Final Report Daad13 02 C 0015 Part5 App L P
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Final Report Daad13 02 C 0015 Part5 App L P Final Report Daad13 02 C 0015 Part5 App L P Document Transcript

  • CRC Book Chapter 5 Draft Appendix L Surface-enhanced Raman detection of chemical agents in water Steven Christesen, Kevin Spencer, Stuart Farquharson, Frank Inscore, Kristina Gonser, and Jason Guicheteau I. INTRODUCTION In 1994 and 1995, sarin gas was released in the Japanese cities of Matsumoto and Tokyo,1 respectively bymembers of the AUM Shinrikyo religious cult. Later in 1995, the same group attempted to poison commuters inTokyo with cyanide.1,2 Fortunately, the cyanide producing devices were discovered before they could be used.Although unsophisticated by military standards, the two sarin attacks resulted in 19 deaths and almost 6000 peopleinjured. More than 30 deliberate chemical releases were reported in Japan in 1998 alone causing more deaths andinjuries. The agent used in the Tokyo and Matsumoto attacks (sarin or GB) is one of a class of toxic organophosphorusnerve agents that include soman (GD), tabun (GA), cyclo-sarin GF and VX (no common name). These nerve agentsare particularly toxic and have LD50’s ranging from 24 milligrams per kilogram of body weight for sarin to 0.07mg/kg for VX, where the LD50 is defined as the lethal dose of a liquid agent causing death in 50% of a givenpopulation via percutaneous liquid exposure on bare skin.3 Organophosphorus nerve agents are toxic because theybind to acetylcholinesterase enzymes (AChE) thereby inactivating them and allowing the neurotransmitteracetylcholine to accumulate at synapses. Symptoms of nerve agent poisoning include twitching, pinpointed pupils,convulsions, coma, and eventually death if the level of exposure is high enough. The threat of terrorism within the United States became a reality in 2001 with the attacks on the Pentagonbuilding and the World Trade Center towers. The mailing of anthrax, shortly thereafter, and the salmonellapoisonings of salad bars in Oregon by the followers of Bhagwan Shree Rajneesh are just two examples of biologicalterrorism in the US. The variety of terrorist attacks and the widespread use of GA, GB, and GF in the Iraq/Iran warsuggest that chemical warfare agents must be considered as a potential weapon against the US. Although themajority of these incidents have involved vapor or aerosol dispersal of the agent, the threat to water supplies isobvious and techniques for quickly and accurately identifying the threat are needed. The Army’s water quality standards for allowable chemical agent contamination levels in drinking water arepublished in the Department of the Army’s Technical Bulletin TB MED 577 Sanitary Control and Surveillance ofField Water Supplies.4 This document is in the process of being updated to include new standards for chemical agentcontamination. The new standards are expected to conform generally to the recommendations of the NationalAcademy of Sciences (NAS) Subcommittee on Guidelines for Military Field Drinking-Water Quality,5 which areshown in Table 1. In the case of nerve agents, these limits are based on a modeled 25% inhibition of AChE, andrepresent a “no observed adverse effect level” (NOAEL). Another class of chemical agents is the vesicants that include sulfur mustard (HD), three variations of nitrogenmustard (HN-1, HN-2, and HN-3), and lewisite (L). The ingestion of low concentrations of HD in water is expectedto result in gastrointestinal irritation. Based on toxicity studies on rats, the military guideline limits were set at 47µg/L and 140 µg/L for water consumption rates of 15 and 5 liters/day, respectively. Although used in World War I,and by the Aum Shinrikyo terroists, hydrogen cyanide is not considered a militarily significant agent due to its highvolatility and rapid detoxification by humans. Environmental cyanide contamination of water, however, can occuras the result of industrial processes such as electroplating and metal polishing. Cyanide is not nearly as toxic as thenerve agents or mustard, but its ready availability lends itself to possible use by terrorists to poison water supplies. The military’s M272 water testing kit, first fielded in 1984, is currently used to detect and identify chemicalagents in treated and source water. Agents are detected via color changing reactions with sensitivities of 0.02 mg/Lfor nerve agents, 2 mg/L for mustard and lewisite, and 20 mg/L for cyanide.6 In general, the M272 is very sensitiveand meets the current requirements listed in TB MED 577, but it is not sufficiently sensitive to ensure that watermeets the recommended water quality standards shown in Table 1. In addition, the vials and chemicals used in thekit are not easily manipulated when wearing a protective suit, mask, and gloves. In an effort to meet military and national security needs for detecting chemical agents in water,sophisticated laboratory methods have been investigated with reasonable success. More than a decade ago, Black etal. demonstrated the ability of combining gas chromatography with mass spectrometry detection (GC/MS) tomeasure sarin and mustard.7 Sega at al. used GC with a phosphorous-selective flame ionization detector to analyzenerve agent hydrolysis products in groundwater,8 while several researchers used capillary electrophoresis (CE) tomeasure chemical warfare agents and their hydrolysis products.9, 10, 11 The sensitivity of these techniques hasimproved by two orders of magnitude from 1 mg/L to 0.01 mg/L in 10 years. A comprehensive development of 1
  • CRC Book Chapter 5 Draftthese techniques was undertaken by Creasy et al. in analyzing chemical weapon decontamination waste from theJohnston Atoll.12,13 These researchers used GC/MS for nerve agents, GC coupled atomic emission detection forarsenic compounds, LC/MS for mustard compounds, and CE with ultraviolet absorption detection for alkylphosphonic acids. Detection limits of 0.02 and 0.140 mg/L were reported for nerve agents and mustard,respectively. Detection of the alkyl phosphonic acids have proven more difficult, and Liu, Hu and Xie recently usedGC/MS to detect mg/L concentrations of these degradation products.14 However, they concede that all of theseseparation methods require extraction, derivatization, and repeated column calibration, making them labor intensive,time consuming (typically 30 to 60 minutes), and less than desirable for field use. Another variant of theseseparation/mass detection technologies is ion mobility spectrometry (IMS).15 This technology has been successfullydeveloped to measure explosives in air samples, and commercial products can be found at most airports.16 Eicemanet al. have investigated the ability of IMS to measure organophosphorous compounds in air,17 while Steiner et al.have investigated IMS to measure chemical agent simulants in water.18 In the latter case, electrospray ionizationwas coupled to the sample entry point of an IMS, and a time-of-flight MS was added as an orthogonal detector.Water samples spiked with 10 mg/L diisopropylmethylphosponate and thiodiglycol could be measured in 1-min,once sample pretreatment was accomplished. It is worth noting that with proper care these MS-based technologiesare likely to detect chemical agents with virtually no false-positives, but detection limits are still insufficient by 1 to2 orders of magnitude in the case of nerve agents and their hydrolysis products. Raman spectroscopy, using both NIR19 and UV20 laser excitation, has found military application for thedetection and identification of chemical agents. The highly selective nature of the Raman spectrum makes thistechnology ideal for non-intrusive and/or short range remote detection of highly concentrated samples. But the tracelevel detection sensitivity required for chemical agents in water is beyond the capabilities of normal Ramanspectroscopy. Improved sensitivity, however, can be achieved with surface-enhanced Raman spectroscopy (SERS).Work by Vo-Dinh on the SERS detection of organophosphorus insecticides21 and organophosphonate vapors22 usingsilver coated spheres and oxidized silver foils, respectively, demonstrated the potential efficacy of SERS for nerveagent detection. More recently, two different SERS substrates, one produced by electrochemical roughening ofsilver or gold foils23 and one produced by gold- or silver-doped sol-gels24,25 were used to measure the primaryhydrolysis of nerve agents, methyl phosphonic acid, with detection limits of 50 to 100 µg/L, respectively. In orderto develop a SERS sensor for detecting chemical agents in water, however, sensitivity and reproducibility need to bedemonstrated for actual chemical agents in all classes. To this end, results on the detection of VX, HD, CN, andtheir hydrolysis products using SERS these substrates are presented. II. EXPERIMENTALA. SERS Substrates 1. Electrochemically Roughened Silver Foils The electrochemically roughened silver substrate foils (EIC Laboratories, Inc., Norwood, MA) were prepared asdescribed in Reference 26 from silver foil coupons (Surepure) cut to a size of ¼” x ½” on a dedicated jeweler’s saw.The cut edges and faces were smoothed to mirror flatness using 0.3 µm Al2O3 polish then washed and stored in 0.1M KOH solution prior to electrochemical roughening in 0.1 M KCl using a platinum gauze counter electrode.Roughening was accomplished by cycling 20 times at a sweep rate of 10 mV/s with upper and lower limits of 0.25and -0.6V versus silver/silver chloride, respectively. The silver substrate foils were electrochemically cleaned atcathodic potential to remove chemical impurities and then soaked overnight in water to remove excess chloride ion.These foils were then electrochemically cycled in sodium hydroxide to create a thick hydroxide layer, whichstabilizes the silver chemistry and reduces its propensity for oxidation. The gold and silver foils were shipped to USArmy Chemical Biological Center (ECBC) for agent testing and generally used within a week of manufacture. Allmeasurements were made by either dipping the foil directly into the solution or by spotting the foil with less than 10µL of the analyte in water. In both cases, the sample was allowed to dry on the substrate foil before recording theSER spectrum. 2. Silver- or Gold-Doped Sol-Gels The sol-gel coated vials were prepared by Real-Time Analyzers, Inc. (RTA, Middletown, CT) using procedurespreviously published by Farquharson et al.27 Silver-doped sol-gels were formed by adding ammonium hydroxide toa solution of silver nitrate, tetramethyl orthosilicate (TMOS), and methanol. Gold-doped sol-gels were coated by 2
  • CRC Book Chapter 5 Draftadding nitric acid to a solution of gold tetrachloride, TMOS and methanol. The two precursor solutions wereprepared, mixed, and transferred to 2-ml glass vials, dried and heated. After sol-gel formation, the incorporatedmetal ions were reduced with dilute sodium borohydride (1 mg/ml), followed by a water wash to remove residualreducing agent. The sol-gel vials were produced at RTA and shipped to ECBC for testing. In all cases, the vialswere filled with the desired agent in solution, capped, and then the SER spectrum was recorded.B. Sample Preparation Stock solutions of HD, VX, and EA2192 were prepared at the ECBC by using Chemical Agent AnalyticalReference Material (CASARM)-Grade neat agent (95+ % purity). Cyanide solutions were made by dissolving KCN(Aldrich) in DI water. For the measurements using the roughened metal foils, the samples were prepared bydissolving the neat agent in distilled, deionized (DI) water at approximately 1 mg/ml and making serial,volumetrically dilutions to achieve the lower concentrations. For the measurements using silver- and gold-dopedsol-gel coated vials the neat agents were dissolved in 2-propanol prior to the addition of DI water. In this case,samples of several concentrations were prepared just prior to the start of each test. The percentage of 2-propanolwas kept constant throughout the volumetric dilution series. Typically, the HD and VX samples contained 1.1 %and 2.0 % 2-propanol, respectively.C. Instrumentation Tests were preformed using two different Raman instruments. For the measurements with roughened silverfoils, a dispersive Raman spectrometer, comprised of a 785 nm diode laser (300 mW), an echelle spectrograph, anda TE cooled CCD camera operating at approximately 45°C below ambient (model RS2000, InPhotonics, Norwood,MA), was used to acquire 1 cm-1 resolution spectra.19 The laser was fiber optically coupled to a sample chamberbox using a RamanProbeTM (InPhotonics). The probe both conveyed the laser light to the sample and served as anoptical filtering device to remove background signals arising in the fiber optic cable. For measurements using sol-gel coated vials, a Fourier transform Raman spectrometer (model IRA-785, Real-Time Analyzers) equipped with a silicon photo-avalanche detector (Perkin Elmer model C30902S, Stamford, CT)was used to acquire spectra at a resolution of 8 cm-1. A 785 nm diode laser (model 785-600, Process Instruments,Salt Lake City, UT) delivered approximately100 mW of power to the sample through a 30 foot fiber optic cable,such that the instrument could be located outside the lab for added safety. The sample system consisted of an XYpositioning stage (Conix Research, Springfield, OR) on which the vials were mounted horizontally just inside thefocal point of an f/0.7 aspheric lens. This lens and the other optics within the fiber optic probe have been previouslydescribed.27 III. RESULTS AND DISCUSSIONA. HD and TDGSulfur mustard (bis(2-chloroethyl) sulfide) hydrolyzes to form mustard chlorohydrin (2-chloroethyl 2-hydroxyethylsulfide), which then hydrolyses to thiodiglycol (TDG). These reactions progress through cyclic sulfonium ionintermediates as shown in Figure 1. Although HD rapidly hydrolyzes to TDG (Table 2), the rate is limited by itslow solubility and solvation rate.28 HD hydrolysis approaches an SN1 mechanism via the pathway shown in Figure 1only when predissolved in organic solvent and at low concentrations (less than 0.001 M or 160 mg/L).29 At theinterface of the HD droplet with water, the sulfonium ions can also interact with TDG to form stable sulfonium salts,such as HD-TDG, CH-TDG, and H-2TDG (Figure 2). The presence of multiple stable HD conformers and theformation of the sulfonium salts complicate the analysis of the SER spectra of sulfur mustard in treated water. The SER spectra of HD in water are dominated by a broad peak with a maximum intensity at 620 cm-1, for bothelectrochemically roughened silver foils and silver-doped sol-gel coated vials, and at 610 cm-1 for gold-doped sol-gel vials. This broad peak aligns with the series of peaks observed between 600 and 800 cm-1 in the normal Ramanspectrum of HD and can be ascribed to the C-S and C-Cl stretching modes (Figure 3).30,31,32 At least two additionalpeaks appear in the spectra at 1003 and 1292 cm-1 for the silver foils, and at 1007 and 1290 cm-1 for the gold-dopedsol-gels. Based on the Raman peaks at 1038 and 1292 cm-1, these peaks are assigned to a C-C stretching mode and aCH2 bend.33 The shift in the C-C stretch is also observed in the C-S or C-Cl stretch. These shifts are consistent with thosereported in the literature by Joo et al.34 for diethyl sulfide (DES) on silver. They report an approximate 20 cm-1 shiftof the C-S stretching modes of the different conformers, and suggest that this is due to DES binding to the surface 3 View slide
  • CRC Book Chapter 5 Draftvia the sulfur atom. The general shift here suggests that it is likely that HD also binds via the sulfur atom. Thesilver foil spectra also contain a peak at 722 cm-1, which is absent or at least weak in both sol-gel spectra. There areat least four possible explanations as to the source of this peak. 1) In the case of the silver foils, the samples weremeasured dried, while the sol-gels were measured in solution, and the 722 cm-1 may represent a different conformeron the surface. 2) The HD was dissolved in water for the foils, and in a combination water and organic solvent forthe sol-gel vials. The latter co-solvent should dramatically increase solvation, expedite hydrolysis and the removalof the terminal chlorines. If so, then the 722 cm-1 peak may be assigned to a C-Cl stretching mode. This issupported by the fact that thiodiglycol does not have this peak, at least under some measurement conditions. 3) The722 cm-1 peak could be due to the formation of one of the sulfonium salts (Figure 2), but these salts are more likelyto contribute new peaks to the sol-gel spectra, not the foil spectra. 4) It was also noted that this peak was moreintense than the 620 cm-1 peak in some foil measurements, and it may alternatively be assigned to a photo-degradation product. This is supported by the generation of a peak at the same frequency in photo-degraded TDG.35Furthermore, at high laser powers and long exposures (several minutes) additional peaks (e.g. 668 cm-1) alsoappeared in HD SER spectra using the gold-doped vials, supporting the assignment of the 722 cm-1 peak to photo-degradation. HD was consistently measured at approximately 50 mg/L using the silver foils (e.g. Figure 3C), andoccasionally at 100 mg/L for the silver-doped sol-gels. Both substrates provided repeatable measurements of 1 g/Lfor HD (e.g. Figure 3B). However, the reproducibility of the SER signal intensity for HD was highly variable at 777mg/L using the silver foils, but considerably better at 1000 mg/L using the silver-doped sol-gels.36 It is not clear,however, how much of the variability in the former is the result of non-reproducibility in the substrate or the dryingprocess, or how much might be explained by the complex and changing mixture of mustard hydrolysis products. The SER spectrum of thiodiglycol was only measured using silver-doped sol-gels. Initial measurements at 1000mg/mL yielded a high quality spectrum that was consistent with SERS of HD and the Raman spectrum of TDG(Figure 4). The SER spectrum is dominated by three peaks at 627, 715, and 1008 cm-1, while the Raman spectrum isdominated by peaks at 652 and 1005 cm-1, which can be assigned to S-C and C-C stretching modes, respectively.Although the 715 cm-1 peak could correspond to either of two weak Raman peaks at 680 and 728 cm-1, it was absentin recent SER measurements of TDG in a flowing stream.35 Here, measurements at low laser powers (15 mW,Figure 4B) confirm that this peak, as well as the 1008 cm-1 peak, are likely due to photo-degradation. Thisconclusion also supports the assignment of the 722 cm-1 peak in the HD SER spectra to a TDG photo-degradationproduct.B. VX, EA2192, and EMPA VX (ethyl S-2-diisopropylamino ethyl methylphosphonothioate) hydrolyzes in distilled water via the pathwaysshown in Figure 537,38,39 with a half-life of greater than 3 days.40 The hydrolysis product EA2192 is itself highlytoxic and much more stable in water, although it will eventually hydrolyze to 2-(diisopropylamino) ethanethiol(DIASH). The ethyl methylphosphonic acid (EMPA) product of Reaction Pathway 1 can also undergo furtherhydrolysis to methylphosphonic acid (MPA). Both the silver foils and sol-gels produced SER spectra that had manyspectra features in common with each other and the normal Raman spectrum (Figure 6). In particular, at least threeoverlapping peaks are seen in all three spectra between 425 and 575 cm-1. Farquharson et al. have assigned thepeaks at 460, 485, and ~530 cm-1 to a POn bending mode, an NC3 stretching mode, and a POnS bending mode,respectively (Table 3).41 Neither substrate provided good sensitivity for VX. The sol-gels provided goodreproducibility at 1000 mg/L (Figure 6B), but only occasionally was a spectrum observed at 100 mg/L, whereas thefoils produced spectra at 100 mg/L on most attempts (Figure 6A). In the case of the latter, a large backgroundcontribution above 800 cm-1, was removed by baseline correction. EA2192 (ethyl S-2-diisopropylamino methylphosphonothioate) the primary hydrolysis product of VX followingReaction Pathway 2 (Figure 5) produced very similar SER spectra using silver foils or silver-doped sol-gels (Figure7). In fact, a high quality spectrum is obtained using the foils at 113 mg/L with peaks at 481, 584, 622, 700, 743,780, 810, 830, 942, 974, 1040, 1120, 1366, 1442, and 1461 cm-1. Many of these peaks have been assignedpreviously (Table 3).41 The SER spectra are however, considerably different than the Raman spectrum of EA2192(Figure 7C). Most notably, the 1055 and 1185 cm-1 peaks, assigned to a PO2S stretch and NC stretch, in the Ramanspectrum are absent in the SER spectra. It is surprising that the PO2S stretch is not SER-active, and its assignmentmay be in doubt. It is also worth noting that the most intense peak in the SER spectra at 942 cm-1, assigned to anNC3 stretch, also dominated the SER spectrum of DIASH.41 4 View slide
  • CRC Book Chapter 5 Draft The silver foils provided reasonable sensitivity for EA2192 and spectra were obtained at a number ofconcentrations to as low as 33 mg/L. The silver-doped sol-gels successfully measured 1000 mg/L, but no lowerconcentrations were tried. The SER spectra for EMPA are more interesting (Figure 8), in that both the sol-gel and foil spectra appear tocontain photo-degradation products. In the case of silver-doped sol-gels, a spectrum can be obtained that has manyof the same features as found in the normal Raman spectrum, as long as low laser powers are used (30 mW, Figure8B). Peaks occur at 505, 730, 792, 893, 1047, 1098, 1293, 1420, and 1454 cm-1 in both spectra, which all have beenassigned.41 The primary difference between the two spectra is that a second intense peak occurs at 745 cm-1, albeitthe normal Raman spectrum contains a shoulder at close to this frequency. As soon as the laser power is increasedto 100 mW, this peak increases in intensity substantially, indicating photo-degradation (Figure 8A). This effect iseven more dramatic for the silver foils, where the this peak completely replaces the 730 cm-1 peak, especially at lowconcentrations (100 µg/L, Figure 8D). Additional peaks also grow in at 610, 915, and 955 cm-1. It is reasonable toassign the 745 cm-1 peak to the formation of methyl phosphonic acid, since it has a dominant peak at 755 cm-1, butMPA does not contain the latter three peaks, and it is unclear as to composition of the degradation product. It isclear from the data that EMPA degrades rapidly in the presence of silver and laser irradiation.C. Cyanide Hydrogen cyanide (AC) is a highly volatile liquid (boiling point of 25.7 °C) belonging to a class of chemicalagents known as blood agents. It has commercial uses in the extraction of gold from ore and in the manufacture ofother chemicals, such as acrylonitrile and methyl methacrylate. AC is highly soluble in water and hydrolyzes slowlyto ammonia and formic acid. Hydrogen cyanide and its potassium and sodium salts release toxic free cyanide (CN)when dissolved in weak acids such as water. Cyanide’s toxicity results from its attack on the enzyme cytochromeoxidase thereby preventing cell respiration and the normal transfer of oxygen from the blood to body tissues. Research in the past focused on the gold mining and textile industries’ concerns over cyanide leakage into thegroundwater and the EPA’s limit of 1 part per million or less of CN in detoxified industrial waste. The majority ofthese SERS techniques not only yield detection limits below the EPA mandate but well into the low part per billionrange. Detection of cyanide has also become somewhat of a standard assessment of a SERS substrate’s capabilityand sensitivity. SERS applications utilizing gold nanostructures,42,43,44 silver electrodes,45,46,47,48,49 sol-gels,25,50 andothers51,52 have reported great success at detecting CN in a variety of forms. The success can be attributed to thehigh binding efficiency of –(C≡N) to the metal surface resulting in a distinct band between 2120-2150 whoseposition is dependent on pH and concentration.25,42 Both silver- and gold-doped sol-gel vials have been used to measure cyanide in water to 1 mg/L and below(Figure 9A). In fact very reproducible measurements have been made at 10 mg/L. Both electrochemicallyroughened silver and gold foils have successfully been used to measure low concentrations of cyanide, and in thecase of the latter, consistent measurements down to 20 µg/L. The SER signal strength is highly variable, however,as seen for cyanide in water at 200 µg/L (Figure 9B). Data collected on the same day (but different gold foils) weremore consistent than measurements on different days, indicating that the substrates may be changing in storage orshipment. This is illustrated by a fit of the data from the two days by a Langmuir adsorption isotherm (Figure 10).This isotherm can be used to describe both physical and chemical adsorption:53 Kc θ= (1) Kc + 1 The cyanide concentration is given by c, the fractional surface coverage by θ , and the adsorption equilibriumconstant by K. The fractional coverage is calculated as the ratio of the SERS peak intensity divided by the intensityat full surface coverage (I/Imax). In this analysis, both K and Imax were fit using a nonlinear regression technique(DataFit, Oakdale Engineering, Oakdale, PA). The calculated adsorption equilibrium constants for the two days area factor of 10 different (0.4 L/mg vs. 0.04 L/mg). IV. CONCLUSIONS The potential sensitivity and selectivity of SERS coupled with the lack of strong water interference make it anattractive technique for chemical detection in aqueous solution. Two very different SERS-active substrates, 5
  • CRC Book Chapter 5 Draftelectrochemically roughened gold and silver foils, and gold- and silver-doped sol-gels both proved capable ofmeasuring sulfur mustard, VX, cyanide and several hydrolysis products of these chemical agents. However, only inthe case of cyanide was sensitivity sufficient for a SERS-based chemical agent water monitor. Substantialimprovements in sensitivity are required for the other agents. Furthermore, low laser powers are required tominimize photo-degradation. Finally, the ability to manufacture substrates that yield reproducible results remainselusive. Nevertheless, the detection limits for some of the phosphonic acid nerve agent hydrolysis products andcyanide show promise. Efforts to improve sensitivity and reproducibility will continue to be pursued.Table 1. Recommended Field Drinking Water Guidelines CONSUMPTION RATE Chemical Agent 5 L/day 15 L/day Cyanide (µg/L) 6000 2000 Sulfur mustard (µg/L) 140.0 47.0 Nerve agents (µg/L) GA 70 22.5 GB 13.8 4.6 GD 6.0 2.0 VX 7.5 2.5Table 2. Hydrolysis half-lives and solubilities of chemical agents and their primary hydrolysis products. Chemical Water Solubility (at Hydrolysis ½ life Agent 25°C) Sarin (GB) 39 hr (pH 7) completely miscible IMPA stable but can hydrolyze to MPA 4.8 g/L MPA very stable >1000 g/L VX >3 days (pH 7) 150 g/L EA2192 > 10 x VX ∞ sol. DIASH stable ca. 1000 g/L EMPA >8 days 180 g/L MPA very stable >1000 g/L HD 5 min 0.648 g/L* Mustard 3 min** Chlorohydrin TDG stable 6900 g/L*Seidell A. 1941. Solubilities of organic compounds. A compilation of quantitative solubility data from theperiodical literature. Vol. 11, 3rd Edition. New York: D. Van Nostrand Company, Inc. 241-242.**Ogston, A. G.; Holiday, E. R.; Philpot, J. St. L.; Stocken, L. A., Trans. Faraday Soc., 1948, 44, 45-52. 6
  • CRC Book Chapter 5 DraftTable 3. Tentative vibrational mode assignments for EA2192 and VX:41 Normal Raman, Sol-gel SER, andRoughened Ag SER. EA2192 VX Sol-Gel Roughened Sol-Gel Roughened NR NR Tentative Assignments SER* Ag SER SER* Ag SER 386 387 372 376 SPO bend 418 413 CC or CN bend 453 456 461 458 441 POn bend 484 481 481 484 484 487 NC3 breathing 499 POn bend 513 526 523 528 539 532 POn(S) bend 587 584 586 NCn bend 645 623 667 622 PSC bend CSH bend 693 700 696 682 CS stretch 732 735 743 744 731 735 PC stretch + backbone (CPOCC) 769 769 771 PC stretch and/or backbone 814 811 811 805 SC stretch + NC3 breathing 831 830 830 836 820 863 856 CH3 bend 905 891 883 891 885 889 OPC stretch / CCN stretch 925 947 939 943 931 939 940 NC3 stretch 966 971 975 965 POn stretch 1010 1006 1015 1006 1009 POn or CH3 bend 1043 1040 1029 1031 SCCN bend 1054 PO2(S) stretch 1100 1100 1101 1096 1098 OC or CC stretch 1132 1125 1128 1121 1125 NC stretch 1183 1183 1170 NC stretch 1219 1214 1220 NC stretch 1229 1228 1237 CH2 bend 1306 1300 1300 1301 CH3 bend 1329 1327 1329 1343 CN bend + CC bend 1366 1365 1369 1366 1399 1399 1394 1400 CH3 bend / NC3 stretch 1418 CH3 bend 1427 1423 1443 1439 1439 CH2 bend 1451 1446 CHn bend 1460 1464 1463 1462 1462 1461 CHn bend 1493 7
  • CRC Book Chapter 5 Draft + S H2O S H2O SCl Cl Cl + Cl- Cl OH + HCl I Mustard HD Chlorohydrin CH + S H2O S - H2O SCl OH HO + Cl HO OH + HCl II TDGFigure 1. HD hydrolysis pathway. S SCl S+ HO S+ HO OH HO OH H-TDG CH-TDG OH S S + S+ HO HO OH H-2TDGFigure 2. Sulfonium salts produced in reaction of I and II (Figure 1) with TDG. 8
  • CRC Book Chapter 5 DraftFigure 3. SERS of HD using A) gold-doped sol-gel, B) silver-doped sol-gel, and C) electrochemically roughenedsilver foil. D) Raman spectrum of HD. Conditions: A) and B) 1 g/L in isopropanol/water, 100 mW of 785 nm, 1-min, C) 0.777 g/L in distilled water, 100 mW of 785 nm, 0.5-min, D) neat HD, 300 mW of 785 nm, 1-min.Figure 4. SERS of TDG using silver-doped sol-gels using A) 100 and B) 15 mW of 785 nm excitation, and C)Raman of neat TDG. Conditions: A) and B) 1 g/L, and C) 300 mW. 9
  • CRC Book Chapter 5 Draft OH 1 H N + O P O S 34%-37% DIASH EMPA O S O P N H2O 2 S P N O + EtOH 42%-50% O VX H EA2192 3 S- N ~10% O P O + HO O-ethyl 2-(diisopropylamino) methylphosphonothioate ethanolFigure 5. VX hydrolysis pathways.Figure 6. SERS of VX using A) roughened silver foil and B) silver-doped sol-gel, and C) Raman spectrum of neatVX. Conditions: A) 1 g/mL B) 129 mg/L. 10
  • CRC Book Chapter 5 DraftFigure 7. SERS of EA2192 using A) silver-doped sol-gel vial and B) roughened silver foil, and C) Raman spectrumof solid EA2192. Conditions: A) 1 g/L, B) 113 mg/L. The substrate was dipped into the solution for 2 minutes priorto collecting a 0.5 min spectrum.Figure 8. SERS of EMPA in silver-doped-sol-gel vials using A) 100 and B) 30 mW of 785 nm excitiation. SERS ofEMPA on electrochemically roughened silver foils for D) 0.1 and E) 1 mg/L samples. Raman spectra of neat EMPAin C) and E) for comparison. Conditions A) and B) 1 g/L, ... 11
  • CRC Book Chapter 5 DraftFigure 9. SER spectra of sodium cyanide A) in three different silver-doped sol-gel coated vials at 1, 10, and 100mg/L and B) on four different roughened gold foils all at 0.2 mg/L. Conditions: A) 100 mw 785 nm, 1-min, 8, B)300 mw 785 nm, 0.5-min, 1. The top two traces were measured on the same day, as were the bottom two traces. 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 1 10 100 1000 10000 100000 1000000 Concentration (µg/L)Figure 10. Plot of surface coverage (θ) vs. concentration for CN on electrochemically roughened gold. Thediamonds and open circles are results from two different days, and each point represents data from a differentsubstrate. The solid line and dashed line are fits of the data to the Langmuir adsorption isotherm and have R2 valuesof 0.971 and 0.944, respectively. 12
  • CRC Book Chapter 5 Draft References1 Global Proliferation of Weapons of Mass Destruction: A Case Study on the Aum Shinrikyo, The Senate Government Affairs Permanent Subcommittee on Investigations, October 31, 1995 Staff Statement, http://www.fas.org/irp/congress/1995_rpt/aum/index.html,2 The Japan Times Online Tuesday July 18, 2000. http://www.japantimes.co.jp/cgi- bin/getarticle.pl5?nn20000718a1.htm.3 Committee on Toxicology. Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents, Nat. Acad. Press (Washington, D.C.) 1997.4 http://chppm-www.apgea.army.mil/documents/TBMEDS/TBMED577.pdf5 Committee on Toxicology. Guidelines for Chemical Warfare Agents in Military Field Drinking Water, Nat. Acad. Press (Washington, D.C.) 19956 McKone, T.E., Huey, B.M., Downing, E., and Duffy, L.M., Strategies to Protect the Health of Deployed U.S. Forces: Detecting, Characterizing, and Documenting Exposures, Division of Military Science and Technology and Board on Environmental Studies and Toxicology, National Research Council, NATIONAL ACADEMY PRESS, Washington, D.C.,207, 2000. http://www.nap.edu/books/0309068754/html.7 . R.M. Black, R.J. Clarke, R.W. Read, M.T. Reid: J. Chromat. 662, 301 (1994)8 . G.A. Sega, B.A. Tomkins, W.H. Griest: J Chromat. A 790, 143 (1997)9 . S.A. Oehrle, P.C. Bossle: J. Chromat. A 692, 247 (1995)10 . J.E. Melanson, B.L-Y. Wong, C.A. Boulet, C.A. Lucy: J. Chromat. A 920, 359 (2001)11 . J. Wang, M. Pumera, G.E. Collins, A. Mulchandani: Anal. Chem. 74, 6121 (2002)12 . W. Creasy, M. Brickhouse, K. Morrissey, J. Stuff, R. Cheicante, J. Ruth, J. Mays, B. Williams, R. O’Connor, H. Durst: Environ. Sci. Technol. 33, 2157 (1999)13 . W.R. Creasy: Am. Soc. Mass. Spectrom. 10, 440 (1999)14 . Q. Liu, X. Hu, J. Xie: Anal. Chim. Acta 512, 93 (2004)15 . G.A. Eiceman, Z. Caras: Ion Mobility Spectrometry. (CRC Press, 1994)16 . See products from Smiths Detection, Bruker Daltronics, etc.17 . N. Krylova, E. Krylov, G.A. Eiceman: J. Phys. Chem. 107, 3648 (2003)18 . W.E. Steiner, B.H. Clowers, L.M. Matz,W.F. Siems, H.H. Hill Jr.: Anal. Chem. 74, 4343 (2002)19 Christesen, S., MacIver, B., Procell, L., Sorrick, D., Carrabba, M., and Bello, J., Non-intrusive analysis of chemical agent identification sets (CAIS) using a portable fiber-optic Raman spectrometer, Appl. Spectr., 53, 850, 1999.20 Sedlacek III, A.J., Christesen, S.D., Chyba, T., and Ponsardin, P., Application of UV-Raman spectroscopy to the detection of chemical and biological threats, in Proc. SPIE Vol. 5269, Sedlacek III, A.J, Christesen, S.D., Colton, R. and Vo-Dinh, T., Eds., SPIE, Bellingham, Washington, 2004, 23.21 Alak, A.M. and Vo-Dinh, T., Surface-enhanced Raman spectrometry of organophosphorus chemical agents, Anal. Chem., 59, 2149, 1987.22 Taranenko, N., Alarie, J-P., Stokes, D.L., VoDinh, T., Surface-enhanced Raman detection of nerve agent simulant (DMMP and DIMP) vapor on electrochemically prepared silver oxide substrates, J. Raman Spectrosc., 27, 379, 1996.23 Spencer, K., Sylvia, J., Clauson, S. Janni, J., Surface-enhanced Raman as a water monitor for warfare agents, in Proc. SPIE Vol. 4577, Christesen, S.D. and Sedlacek III, A.J, Eds., SPIE, Bellingham, Washington, 2002, 15824 Farquharson, S., P. Maksymiuk, K. Ong, and S. Christesen, Chemical agent identification by surface-enhanced Raman spectroscopy, in Proc. SPIE Vol. 4577, Christesen, S.D. and Sedlacek III, A.J, Eds., SPIE, Bellingham, Washington, 2002, 166.25 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F. E., and Smith, W. W., pH dependence of methyl phosphonic acid, dipicolinic acid, and cyanide by surface-enhanced Raman spectroscopy, in Proc. SPIE Vol. 5269, Sedlacek III, A.J, Christesen, S.D., Colton, R. and Vo-Dinh, T., Eds., SPIE, Bellingham, Washington, 2004, 117.26 Spencer, K.M., Sylvia, J.M., Marren, P.J., Bertone, J.F., and Christesen, S.D., Surface-enhanced Raman spectroscopy for homeland defense, in Proc. SPIE Vol. 5269, Sedlacek III, A.J, Christesen, S.D., Colton, R. and Vo-Dinh, T., Eds., SPIE, Bellingham, Washington, 2004, 1.27 Farquharson, S, Gift, A., Maksymiuk, P. and Inscore, F., Appl. Spectrosc. 58, 351 (2004).28 Ogsten, A.G.; Holiday, E.R.; Philpot, J. St. L.; Stocken, L. A., The replacement reactions of b,b-dichlorodiethyl sulphide and of some analogues in aqueous solution: the isolation of b-chloro-b-hydroxydiethyl disulphide, Trans. Faraday Soc., 44, 45, 1948. 13
  • CRC Book Chapter 5 Draft29 Yang, Y-C., Szafraniec, L.L, Beaudry, W.T., and Ward, J.R., Kinetics and mechanism of the hydrolysis of 2- chloroethyl sulfides, J. Org. Chem., 53, 3293, 1988.30 Sosa, C., Bartlett, R.J., KuBulat, K. and Person, W.B., A theoretical study of the harmonic vibrational frequencies and infrared intensities of XCH2CH2SCH2CH2X and XCH2CH2SH (X=H, Cl), J. Phys. Chem., 93, 577, 1989.31 Donovan, W.H. and Famini, G.R., Conformational analysis of sulfur mustard from molecular mechanics, semiempirical, and ab initio methods, J. Phys. Chem., 98, 3669, 1994.32 Christesen, S.D., Vibrational spectra and assignments of diethyl sulfide, 2-chlorodiethyl sulfide and 2,2’- dichlorodiethyl sulfide, J. Raman Spectrosc., 22, 459, 1991.33 Donovan, W.H. and Famini, G.R., Jensen, J.O., and Hameka, H.F., Phosphorus, Sulfur, and Silicon, 80, 47, 1993.34 Joo, T.H., Kim, K. and Kim, M.S., Surface-enhanced Raman study of organic sulfides adsorbed on silver, J. Mol. Struct., 162, 191, 1987.35 Inscore, F., and Farquharson, S., Detecting hydrolysis products of blister agents in water by surface-enhanced Raman spectroscopy, in Proc. SPIE Vol. 5993, Vo-Dinh, T., Lieberman, R.A., and Gauglitz, G., Eds., SPIE, Bellingham, Washington, 2005, 19.36 Farquharson, S., A. Gift, P. Maksymiuk, F. Inscore, W. Smith, K. Morrisey, and S.D. Christesen, Chemical agent detection by surface-enhanced Raman spectroscopy, in Proc. SPIE Vol. 5269, Sedlacek III, A.J, Christesen, S.D., Colton, R. and Vo-Dinh, T., Eds., SPIE, Bellingham, Washington, 2004, 16.37 www.mitretek.org/home.nsf/homelandsecurity/VX38 Szafraniec, L. J.; Szafraniec, L. L.; Beaudry, W. T.; Ward, J. R., On the Stoichiometry of Phosphonothiolate Ester Hydrolysis, CRDEC-TR-212, July 1990, AD-A25077339 Epstein, J.; Callahan, J. J.; Bauer, V. E., The kinetics and mechanisms of hydrolysis of phophonothiolates in dilute aqueous solution, Phosphorus, 1974, 4, 157-163.40 Yang, Y-C., Chemical detoxification of nerve agent VX, Acc. Chem. Res., 1999, 32, 109-11541 Farquharson, S, Gift, A., Maksymiuk, P. and Inscore, F., Surface-Enhanced Raman Spectra of VX and its Hydrolysis Products, Appl. Spectrosc., 59, 654, 2005.42 Tessier, P. M., Christesen, S. D., Ong, K. K., Clemente, E. M., Lenhoff, A. M., Kaler, E. W., and Velev, O. D., On-line spectroscopic characterization of sodium cyanide with nanostructured gold surface-enhanced Raman spectroscopy substrates, Applied Spectroscopy, 56, 1524, 2002.43 Kuncicky, D. M., Christesen, S. D., and Velev, O. D., Role of the micro- and nanostructure in the performance of SERS substrates assembled from gold nanoparticles, Appl. Spectrosc., 59, 401, 2005.44 Tessier, P. M., Christesen, S. D., Ong, K. K., Clemente, E. M., Lenhoff, A. M., Kaler, E. W., and Velev, O. D., Assembly of gold nanostructured films templated b colloidal crystals and used in surface-enhanced Raman spectroscopy, in Proc. SPIE Vol. 4577, Christesen, S.D. and Sedlacek III, A.J, Eds., SPIE, Bellingham, Washington, 2002, 53.45 Shelton, R. D., Hass, J. W., and Wachter, E. A., Surface-enhanced Raman detection of aqueous cyanide, Appl. Spectrosc., 48, 1007, 1994.46 Mahoney, M. R., and Cooney, R. P., The evidence for stoichiometric silver oxide-cyanide phase in cyanide in cyanide SERS from silver electrodes, Chem. Phys. Lett., 117, 71, 1985.47 Benner, R. E., Dornhaus, R., Chang, R. K., and Laube, B. L., Correlations in the Raman spectra of cyanide complexes adsorbed on silver electrodes with voltammograms, Surf. Sci., 101, 341, 1980.48 Kellogg, D. S. and Pemberton, J. E., Effects of solution conditions on the surface-enhanced Raman scattering of cyanide species at Ag electrodes, J. Phys. Chem., 91, 1120, 1987.49 Billmann, J., Kovacs, G., and Otto, A., Enhanced Raman effect from cyanide adsorbed on a silver electrode, Surf. Sci., 92, 153, 1980.50 Premasiri, W. R., Clarke, R. H., Londhe, S., and Womble, M. E., Determination of cyanide in waste water by low-resolution surface enhanced Raman spectroscopy on sol-gel substrates, J. Raman Spetrosc. 30, 827, 1999.51 Vo-Dinh, T., Surface-enhanced Raman spectroscopy using metallic nanostructures, Trends Anal. Chem., 17, 557, 1998.52 Wachter, E. A., Storey, J. M. E., Sharp, S. L., Carron, K. T., and Jiang, Y., Hybrid substrates for real-time SERS-based chemical sensors, Appl. Spectrosc., 48, 193, 1995.53 Adamson, A.W. and Gast, A.P., Physical Chemistry of Surfaces (Wiley Interscience, New York, 1997), 6th ed., p. 599. 14
  • Springer Book Kneipp Editor Appendix M Draft 125. Detecting chemical agents and their hydrolysis products in water Stuart Farquharson, Frank E. Inscore and Steve Christesen Real-Time Analyzers, Middletown, CT, 0645725.1 INTRODUCTIONThe use of chemicals as weapons was introduced during World War I. It is estimated that chlorine, phosgene andsulfur-mustard (HD) resulted in an estimated death of 100,000 soldiers and 1 million injuries [1]. Over the next 20years, chemicals designed specifically for warfare were developed; this included the substantially more toxic nerveagents, tabun, sarin, and soman (GA, GB, and GD, respectively). Fortunately, these abhorrent chemicals were notused in WWII, as world leaders feared reprisal attacks on their cities. During the Iran-Iraq war in the 1980s, theIraqis used HD, GA, GB, and GF (cyclo-sarin), and in 1988, Saddam Hussein used mustard and possibly nerveagents in killing several thousand Kurds [1].In more recent years, chemical agents have been used by terrorists. In Japan, the Aum Shinrikyo religious cultreleased GB within the Tokyo subway system in 1995 [2]. The release of GB in this confined space had devastatingeffects resulting in 12 fatalities and hospitalization of thousands. This event and the mailing of anthrax causingspores through the US Postal System in 2001 demonstrated that deployment of chemical and biological agents donot require sophisticated delivery systems, and a wide range of attack scenarios must be considered. Among thesescenarios is the deliberate poisoning of drinking water. This includes water supplies used in military operations andwater delivered to major cities from reservoirs and through distribution systems. Countering such an attack requiresdetecting poisons in water rapidly, and at very low concentrations.The required detection sensitivity for each agent depends on several factors, such as toxicity and hydrolysis (Table25.1). In the case of cyanide (AC) it known that 4 milligrams per liter of water produces detectable changes inhuman blood chemistry and 8 mg L-1 causes severe, but reversible symptoms [3]. The military has used this andother toxilogical data to set a field drinking water standard (FDWS) for cyanide at 2 mg L-1 [4]. The FDWSrepresents the maximum allowable concentration that is assumed safe when 15 L of water per day is consumed over5 days (expected soldier intake in arid climates). Human toxicity data for the other chemical warfare agents in waterhave, in general, not been determined. The normal route of exposure for chemical warfare agents is inhalation, andmost of the toxicity data is given as the LCt50s [1], the concentration that is lethal to 50% of an exposed populationas a function of exposure time. In the case of mustard, animal studies along with the inhalation LCt50, the oral lethaldosage of 0.7 mg per kg of body mass (LD50), and modeling studies [5], have been used to set the FDWS at 0.047mg L-1. Similar analyses of LCt50s and LD50s for GB and VX have been used to set their FDWS at 0.0046 and0.0025 mg L-1, respectively. The FDWS concentrations have also been used by the military to set the minimumdetection requirement for poisons in water.Table 25.1. Military field drinking water standard [4], lethal exposures and dosages [1,3,5], and water properties forselected chemical warfare agents. Chemical FDWS LCt50 LD50 Water Hydrolysis Hydrolysis 5-day/15L inhalation oral Solubility Half-Life* Product (mg L-1) (mg-min m-3) (mg kg-1) at 25°C HCN (AC) 2 2000 - - CN NaCN 480 g L-1 Mustard (HD) 0.047 900 0.7 0.92 g L-1 2-30 hours TDG Sarin (GB) 0.0046 70 2 completely 20-40 hours IMPA, MPA miscible VX 0.0025 35 0.07 150 g L-1 82 hours DIASH, EMPA, EA2192, MPAIn order to detect these poisons in water, their properties in water must also be considered, i.e. the solubility, rate ofhydrolysis, and hydrolysis products formed. In the case of cyanide, as HCN, KCN, or NaCN, all of these chemicalsare extremely soluble in water (completely miscible, 716, and 480 g L-1, respectively) [6]. In solution the cyanide
  • Springer Book Kneipp Editor Draft 2ion is formed in equilibrium with the conjugate acid, HCN (Figure 25.1A), according to the Ka of 6.15x10-10 [7 ]. Inthe case of cyanide then it is important to know the pH, if one form of the chemical is to be detected versus theother. For example, if 2 mg L-1 of NaCN is added to water (the FDWS), then 1.25 mg L-1 of CN- and 0.75 mg L-1 ofHCN will be present. A B C DFigure 25.1. Hydrolysis reaction pathways for A) CN, B) HD, C) GB, and D) VX.In the case of sulfur-mustard, the situation is somewhat more complex. It is marginally soluble in water tending toform droplets, and hydrolysis occurs at the droplet surface. This property has made measuring the hydrolysis rateconstant difficult, and half-lives anywhere from 2 to 30 hours are reported [8]. Chemically, the hydrolysis of HDinvolves the sequential replacement of the chlorine atoms by hydroxyl groups through cyclic sulfonium ionintermediates to form thiodiglycol (TDG, Figure 25.1B) [9]. If a median hydrolysis rate is assumed, then earlydetection of poisoned water will require measuring HD, while post-attack or downstream monitoring will requiremeasuring TDG. For sarin, the analysis is more straightforward, since it dissolves readily into water and it is stablefor a day or more. In this case, detecting poisoned water will largely require measuring sarin, while monitoring theattack will require detecting its sequential hydrolysis products, isopropyl methylphosphonic acid (IMPA) and methylphosphonic acid (IMPA, MPA, respectively, Figure 25.1C) [8,10,11]. The other hydrolysis products, hydrofluoricacid and 2-propanol, are too common to provide definitive evidence of water poisoning and their measurementwould be of limited value. VX is reasonably soluble, and like sarin, is fairly persistent with a hydrolysis half-lifegreater than 3 days [12]. Unfortunately, one of its hydrolysis products, known as EA2192, is considered just astoxic as VX, more soluble and more persistent in water [13]. Consequently, detecting the early stages of poisoningwater should focus on measuring VX, while longer term monitoring should focus on EA2192.The earliest technologies developed for CWA detection were based on electrochemical, ionization, or colorimetricanalysis. Examples of the latter include phosgene, M8 and M9 tape, which change color when in contact with asample like pH paper. Although these tapes are easy to use, they are not generally agent specific and suffer from ahigh percentage of false-positives [14]. For example, M8 changes color when in contact with common solvents suchas acetonitrile, ethanol, methanol, or common petroleum products such as brake fluid, lighter fluid, or WD-40 [15].More rigorous laboratory methods have been successfully developed to detect chemical agents with minimum false-positive responses. More than a decade ago, Black et al. demonstrated the ability of combining gas chromatography
  • Springer Book Kneipp Editor Draft 3with mass spectrometry detection (GC/MS) to measure sarin and mustard [16]. Sega at al. used GC with aphosphorous-selective flame ionization detector to analyze nerve agent hydrolysis products in groundwater [17],while several researchers used capillary electrophoresis (CE) to measure chemical warfare agents and theirhydrolysis products [18,19,20]. The sensitivity of these techniques has improved by two orders of magnitude from 1mg L-1 to 0.01 mg L-1 in 10 years. A comprehensive development of these techniques was undertaken by Creasy etal. in analyzing chemical weapon decontamination waste from the Johnston Atoll [11,21]. These researchers usedGC/MS for nerve agents, GC coupled atomic emission detection for arsenic compounds, LC/MS for mustardcompounds, and CE with ultraviolet absorption detection for alkyl phosphonic acids. Detection limits of 0.02 and0.140 mg L-1 were reported for nerve agents and mustard, respectively. Detection of the alkyl phosphonic acidshave proven more difficult, and Liu, Hu and Xie recently used GC/MS to detect mg L-1 concentrations of thesedegradation products [22]. However, they concede that all of these separation methods require extraction,derivatization, and repeated column calibration, making them labor intensive, time consuming (typically 30 to 60minutes), and less than desirable for field use. Another variant of these separation/mass detection technologies is ionmobility spectrometry (IMS) [23]. This technology has been successfully developed to measure explosives in airsamples, and commercial products can be found at most airports [24]. Eiceman et al. have investigated the ability ofIMS to measure organophosphorous compounds in air [25], while Steiner et al. have investigated IMS to measurechemical agent simulants in water [26]. In the latter case, electrospray ionization was coupled to the sample entrypoint of an IMS, and a time-of-flight MS was added as an orthogonal detector. Water samples spiked with 10 mgL-1 diisopropylmethylphosponate and thiodiglycol could be measured in 1-min, once sample pretreatment wasaccomplished. It is worth noting that with proper care these MS-based technologies are likely to detect chemicalagents with virtually no false-positives, but detection limits are still insufficient by 1 to 2 orders of magnitude in thecase of nerve agents and their hydrolysis products.More rapid analysis of agents in the solid, liquid and gas phase has been demonstrated by vibrational spectroscopy[27-31]. Hoffland et al. reported infrared absorbance spectra and absolute Raman cross sections for severalchemical agents [27], while Christesen measured Raman cross sections for sarin, tabun, mustard gas, and VX [28].Again, however these technologies also have limitations. Raman spectroscopy is simply not a very sensitivetechnique, and detection limits are typically 0.1% (1000 ppm). And infrared spectroscopy would have limited valuein analyzing poisoned water, since the very strong infrared absorption of water would obscure most other chemicalspresent. Nevertheless, efforts to overcome these limitations have been demonstrated. Braue and Pannella quantifiedthe G-series nerve agents (tabun, sarin, and soman) in terms of infrared attenuated total reflectance using a circle-cell [29].Enormous improvements in sensitivity for Raman spectroscopy can be achieved through surface-enhancement [32].The interaction of surface plasmon modes of metal particles with target analytes can increase scattering efficiencyby as much 14-orders of magnitude, although 6-orders of magnitude are more common. The details of surface-enhanced Raman spectroscopy (SERS) can be found in the beginning of this book. The utility of SERS to measurechemical agents was first demonstrated by Alak and Vo-Dinh by measuring several organophosphonates assimulants of nerve agents on a silver-coated microsphere substrate [33]. Spencer, et al. used SERS to measurecyanide, MPA, HD and EA2192 on electrochemically roughed gold or silver foils [34,35,36]. However, in all ofthese measurements, the sample needed to be dried on the substrates to obtain the best sensitivity (e.g. 0.05 mg L-1for MPA). More recently, Tessier et al. obtained SERS of 0.04 mg L-1 cyanide in a stream flowing over a substrateformed by a templated self-assembly of gold nanoparticles [37]. However, optimum sensitivity requiredintroduction of an acid wash and the measurements were irreversible.In the past few years, we have also been investigating the ability of SERS to measure chemical agents at 0.001 mgL-1 in water and with sufficient spectral uniqueness to distinguish the agent and its hydrolysis products [38-43]. Inour work, we have developed silver-doped sol-gels as the SERS-active medium. These sol-gels can be coated on theinside walls of glass vials, such that water samples can be added to perform point-analysis, or they can beincorporated into glass capillaries, such that flowing measurements can be performed [44]. Here, both samplingdevices were used to measure and compare SER spectra of AC, HD, VX and several of their hydrolysis products,TDG, EA2192, EMPA, and MPA. In addition, a field-usable Raman analyzer was used to measure 0.01 mg L-1cyanide flowing in water with a detection time of less than 1-min.
  • Springer Book Kneipp Editor Draft 425.2 EXPERIMENTALSodium cyanide, 2-hydroxyethylethyl sulfide (HEES), 2-chloroethylethyl sulfide (CEES) and methylphosphonicacid (MPA) were purchased from Sigma-Aldrich (St. Louis, MO) and used as received. Ethyl methylphosphonicacid (EMPA), isopropyl methylphosphonic acid (IMPA), 2-(diisopropylamino) ethanethiol (DIASH), andthiodiglycol (TDG, bis(2-hydroxyethyl)sulfide) were purchased from Cerilliant (Round Rock, TX). Highly distilledsulfur mustard (HD, bis(2-chloroethyl)sulfide), isopropyl methylphosphonofluoridate (GB), ethyl S-2-diisopropylamino ethyl methylphosphonothioate (VX), and ethyl S-2-diisopropylamino methylphosphonothioate(EA2192) were obtained at the U.S. Army’s Edgewood Chemical Biological Center (Aberdeen, MD) and measuredon-site. All samples were initially prepared in a chemical hood as 1000 parts-per-million (1 g L-1 or 0.1% byvolume, Environmental Protection Agency definition) in HPLC grade water (Fischer Scientific, Fair Lawn, NJ) or insome cases methanol or ethanol (Sigma-Aldrich) to minimize hydrolysis.Once prepared, the samples were transferred into 2-ml glass vials internally coated with a silver-doped sol-gel(Simple SERS Sample Vials, Real-Time Analyzers, Middletown, CT) or drawn by syringe or pump into 1-mmdiameter glass capillaries filled with the same SERS-active material [45,46,47]. In the case of flow measurements, aperistaltic pump (variable flow mini-pump, Control Co., Friendswood, TX) was used to flow the various cyanidesolutions through a SERS-active capillary at 1 mL min-1. The vials or capillaries were placed on aluminum platesmachined to hold the vials or capillaries on a standard XY positioning stage (Conix Research, Springfield, OR),such that the focal point of an f/0.7 aspheric lens was positioned just inside the glass wall. The probe optics andfiber optic interface have been described previously [40]. SER spectra were collected using a Fourier transformRaman spectrometer equipped with a 785 nm diode laser and a silicon photo-avalanche detector (IRA-785, Real-Time Analyzers). All spectra were nominally collected using 100 mW, 8 cm-1 resolution, and 1-min acquisitiontime, unless otherwise noted. Complete experimental details can be found in Reference 48. For added safety, allsamples were measured in a chemical hood. In the case of actual agents measured at Edgewood, the FT-Ramaninstrument was placed outside the laboratory and 30 foot fiber optic and electrical cables were used to allow remoteSERS measurements and plate manipulation.25.3 RESULTS AND DISCUSSION25.3.1 Cyanide. Sodium cyanide completely dissolves in water forming the ions in equilibrium with the conjugateacid, HCN as described above. Concentrations of 1.0, 0.1, and 0.01 mg L-1 result in CN- concentrations of 0.52,0.016, and 0.00021 mg L-1 as the corresponding pH decreases from just above the pKa of 9.21 at 9.24 to 8.48 and7.54. This is significant in that only CN- appears to interact sufficiently with silver to produce a SER spectrum, andno spectral signal is observed below pH 7 (except on electrodes at specific potential conditions [49]). The SERspectra of cyanide are dominated by an intense, broad peak at 2100 cm-1 attributed to the C≡N stretch (Figure 25.2).This mode occurs at 2080 cm-1 in Raman spectra of solutions, and the frequency shift in SER spectra is attributed toa strong surface interaction, which is supported by the appearance of a low frequency peak at 135 cm-1 due to a Ag-CN stretch (not shown). It is also observed that as the concentration decreases, the CN peak shifts to 2140 cm-1.This shift has been attribute to the formation of a tetrahedral Ag(CN)32- surface structure [50], as well as to CNadsorbed to two different surface sites [51]. Alternatively, it has also been suggested that at concentrations near andabove monolayer coverage, the CN- species is forced to adsorb end-on due to crowding, and at lower concentrationsthe molecule can reorient to lie flat. This suggests that the 2100 and 2140 cm-1 peaks correspond to the end-on andflat orientations, respectively. However, a previous concentration study of cyanide on a silver electrode observedthe reverse trend, i.e. greater intensity was observed for the 2100 cm-1 peak at low concentration [49].Repeated measurements of cyanide in the SERS-active vials consistently allowed measuring 1 mg L-1 (1 ppm), butrarely below this concentration (Figure 25.2A). Nevertheless, this sensitivity is in general sufficient for pointsampling of water supplies. In the case of continuous monitoring of water, the capillaries are a more appropriatesampling format, and they also allowed routine measurements at 0.01 mg L-1 and repeatable measurements at 0.001mg L-1 (1 ppb, Figure 25.2B). Employing this format, a 50 mL volume of 0.01 mg L-1 cyanide solution was flowedat 2.5 mL min-1 through a SERS-active capillary, and spectra were recorded every 20 seconds. As Figure 25.3shows, the cyanide peak was easily discerned as soon as the solution entered the capillary and remained relativelystable over the course of the experiment. It is worth noting, as indicated above, that the SERS peak in Figure 25.3 isin fact due to 210 ng L-1!
  • Springer Book Kneipp Editor Draft 5 A BFigure 25.2. Surface enhanced Raman spectra of CN in water in silver-doped sol-gel A) coated glass vials and B)filled glass capillaries. All spectra were recorded using 100 mW of 785 nm in 1-min and at a resolution of 8 cm-1.Figure 25.3. 2100 cm-1 peak height measured during continuous flow of a 0.01 mg L-1 (10 ppb) cyanide in water.Surface-enhanced Raman spectra are shown for 1 and 6 min after sample introduction. A 2.5 mL min-1 flow ratewas used and spectra were recorded every 20 sec using 100 mW of 785 nm.
  • Springer Book Kneipp Editor Draft 625.3.2 HD and CEES. The surface-enhanced Raman spectrum of HD is dominated by a peak at 630 cm-1 with anextended high frequency shoulder composed of at least two peaks evident at 695 and 830 cm-1, as well as amoderately intense peak at 1045 cm-1 (Figure 25.4A). The latter peak is assigned to a CC stretching mode, based onthe assignment for a peak at 1040 cm-1 in the Raman spectrum of HD [52]. The assignment of the 630 cm-1 peak isless straightforward, since the Raman spectrum of HD contains five peaks in this region at 640, 655, 700, 740, and760 cm-1 [40,52]. Theoretical calculations for the Raman spectrum of HD indicate that the first three peaks are dueto CCl stretching modes, and the latter two peaks to CS stretching modes [53]. Based on these calculations, and theexpected interaction between the chlorine atoms and the silver surface, it is reasonable to assign the 630 cm-1 SERSpeak to a CCl mode [40]. However, recent SERS measurements of diethyl sulfide produced a very simple spectrumwith an intense peak at 630 cm-1 [54,55], strongly suggesting CS or CSC stretching modes as the appropriateassignment for this peak [56]. The authors of the theoretical treatment concede that the CCl and CS assignmentscould be reversed [53]. The CS assignment also indicates that HD interacts with the silver surface through the sulfurelectron lone pairs. But, interaction between chlorine and silver is still possible and may be responsible for the 695cm-1 peak. The 830 cm-1 peak is left unassigned. A BFigure 25.4. Surface-enhanced Raman spectra of A) HD in methanol and B) TDG in water. Spectral conditions asin Fig. 25.2, samples were 1 g L-1.The surface-enhanced Raman spectrum of TDG is also dominated by a peak at 630 cm-1 with minor peaks at 820,930, 1210, and 1275 cm-1 (Figure 25.4B). Again, the 630 cm-1 peak is preferably assigned to a CSC stretching modeversus a CCl mode, especially since the chlorines have been replaced by hydroxyl groups. Furthermore, the lack ofa 695 cm-1 peak in the TDG spectrum supports the assignment of this peak in the HD spectrum to a CCl mode. The930, 1210 and 1275 cm-1 SERS peaks are assigned to a CC stretch with CO contribution, and two CH2 deformationmodes (twist, scissors, or wag) based on the assignments for the corresponding peaks at 940, 1230 and 1290 cm-1 inthe Raman spectrum of TDG [52,54 ]. It is worth noting that irradiation at high laser powers or for extended periodsproduces peaks at 715 and 1010 cm-1, which are attributed to a degradation product, such as 2-hydroxy ethanethiol[54].The SERS of CEES is very similar to HD, dominated by a peak at 630 cm-1 that is accordingly assigned to a CS orCSC stretching mode (Figure 25.5A). This peak also has a high frequency shoulder centered at 690 cm-1, and a thirdpeak appears at 720 cm-1 in this region. Again, these can be assigned to CCl or CS modes. The quality of thisspectrum also reveals weak peaks at 1035, 1285, 1410, and 1445 cm-1. Peaks at 1035, 1285, 1425, and 1440 cm-1
  • Springer Book Kneipp Editor Draft 7appear in the Raman spectrum of CEES, and the previous peak assignments are used here [52], i.e. the first peak isassigned to a CC stretch, while the remaining peaks are assigned to various CH2 deformation modes. A BFigure 25.5. Surface-enhanced Raman spectra of A) CEES and B) HEES. Spectral conditions as in Fig. 25.2,samples were 1 g L-1 in methanol.Replacing the chlorine atom of CEES by a hydroxyl group in forming HEES produces SER spectral changesanalogous to those cited above for HD and TDG. Again, the SER spectrum is dominated by an intense peak at 630cm-1 attributed to a CS or CSC stretching mode, and the other CEES peaks in this region, specifically the 720 cm-1peak, disappear (Figure 25.5B). Peaks with modest intensity at 1050 and 1145 cm-1 are assigned to a CC stretchingmode and CH2 deformation, respectively. A new peak at 550 cm-1 is likely due to a skeletal bending mode, such asCSC, SCC, or CCO. Finally, it is worth stating that HD, TDG, CEES, and HEES all produce moderately intensepeaks at 2865 and 2925 cm-1 (not shown), that can be assigned to symmetric and asymmetric CH2 stretching modes.Only a limited number of measurements of HD were performed to evaluate sensitivity, due to the safetyrequirements. HD was repeatedly observed at 1 g L-1 and usually observed at 0.1 g L-1 (100 ppm) in the SERS-active vials [40] But even at the latter concentration, substantial improvements in sensitivity are required toapproach the required 0.05 mg L-1 (50 ppb) sensitivity. More extensive experiments were performed on HD’shydrolysis product, TDG since this chemical is safely handled in a regular chemical lab. Flowing TDG throughSERS-active capillaries allowed repeatable measurements at 10 mg L-1, and routine measurements at 1 mg L-1 (1ppm) [55]. These SERS measurements of TDG suggest that the required HD sensitivity may be achievable usingthis technique. Similar flowing measurements in capillaries for HD, CEES, and HEES have not been performed.25.3.3 Sarin. SERS measurements of GB have not been made, but its primary hydrolysis products, IMPA andMPA, have been measured using the SERS-active vials. The SERS of IMPA is very similar to its Raman spectrum[42], which in turn is very similar to the Raman spectrum of sarin [28]. The SER spectrum is dominated by a peakat 715 cm-1 (Figure 25.6A), which is assigned to a PC or PO plus skeletal stretching mode, as is a weak peak at 770cm-1. These assignments are also consistent with a theoretical treatment of the Raman spectrum for sarin [57].Similarly, a modest peak at 510 cm-1 can be assigned to a PC or PO plus skeletal bending mode. Other SERS peaksof modest intensity occur at 875, 1055, 1415, and 1450 cm-1, and based on the spectral analysis of sarin and theRaman spectrum of IMPA with peaks at 880, 1420, and 1455 cm-1, are assigned to a CCC bend, a PO3 stretch, a CH3bend, and a CH2 rock, respectively.
  • Springer Book Kneipp Editor Draft 8 A B CFigure 25.6. Surface-enhanced Raman spectra of A) IMPA, B) MPA, and C) EMPA. Spectral conditions as in Fig.25.2, samples were 1 g L-1 in water.MPA has been well characterized by infrared and Raman spectroscopy [58,59], as well as normal coordinateanalysis [60], and the literature assignments are used here for the SERS of MPA. The SER spectrum is dominatedby a peak at 755 cm-1, which is assigned to the PC symmetric stretch (Figure 25.6B). In comparison to IMPA, it isclear that removing the isopropyl group shifts this frequency substantially (40 cm-1), as the mode becomes a purerPC stretch. Additional peaks with comparatively little intensity occur at 470, 520, 960, 1040, 1300, and 1420 cm-1,and are assigned to a PO3 bending mode, a C-PO3 bending mode, a PO3 stretching mode, another PO3 bendingmode, and two CH3 deformation modes (twisting and rocking).SERS-active vials allowed repeatable measurements of MPA at 10 mg L-1 and routine measurements at 1 mg L-1,and repeatable measurements of IMPA at 100 mg L-1 and routine measurements at 10 mg L-1. Again, however,substantial improvements in sensitivity are required to achieve the minimum requirement of 0.004 mg L-1.25.3.4 VX. The hydrolysis of VX can occur along two pathways (Figure 25.1D) [11,22], either being converted toDIASH and EMPA or EA2192 and ethanol with the former pathway favored four to one. These products alsohydrolyze, and EMPA forms MPA and ethanol, while EA2192 forms DIASH and MPA. Here the SER spectra ofVX, EA2192 and DIASH are compared, while EMPA is compared to IMPA and MPA.The SER spectrum of VX is similar to its Raman spectrum with corresponding peaks at 375, 460, 540, 730, 1095,1300, 1440, and 1460 cm-1 (Figure 25.7A). Since a computer predicted Raman spectrum contains most of themeasured Raman spectral peaks [43,61], it is used to assign the above SERS peaks respectively to an SPO bend, aCH3-P=O bend, a PO2CS wag, an OPC stretch, a CC stretch, and three CHn bends. As previously described forCEES and HD, the 730 cm-1 peak could alternatively be assigned to a CS stretch, but the SER spectra of thesechemicals suggest otherwise.The SER spectrum of EA2192 is somewhat different than VX with the PO modes having limited intensity and theNC3 modes having significant intensity (Figure 25.7B). Specifically, the EA2192 spectrum has moderately intensepeaks at 480, 585, 940, and 1125 cm-1 that can be assigned to an NC3 breathing mode, an NCC bending mode,another NC3 stretching mode, and a NCC stretching mode. Two additional peaks with significant intensity at 695
  • Springer Book Kneipp Editor Draft 9and 735 cm-1 are assigned to a CS stretching mode and an OPC stretching mode, respectively. Two peaks of modestintensity at 525 and 970 cm-1 are attributed to a PO2S bending mode and a PO2 stretching mode. A B CFigure 25.7. Surface-enhanced Raman spectra of A) VX, B) EA2192, and C) DIASH. Spectral conditions as in Fig.25.2, samples were 1 g L-1 in water.The SER spectrum of DIASH contains most of the NC3 modes cited previously for EA2192 (Figure 25.7C),specifically peaks appear at 480, 585, 940, and 1120 cm-1, and can be assigned as above. Additional peaks at 740,810, and 1030 cm-1, are assigned to CH bending, a combination of SC stretching and NC3 bending, and SCCNbending modes, based on the Raman spectrum of DIASH [43]. A broad peak centered at 695 cm-1 also occurs thathas previously been assigned to an SC stretch, but the frequency and intensity of this mode in the HD and CEESspectra above, makes this assignment less certain.It is worth noting the similarity between the EA2192 and DIASH SER spectra, the principle difference being theaddition of the SCCN bending mode at 1030 cm-1 for the latter. This may simply be due to the fact that bothmolecules interact through the sulfur with the metal surface to similar extents resulting in similar spectra. However,it is also possible that the EA2192 spectrum is of DIASH formed either by hydrolysis or photo-degradation. Sincethe sample was measured within one hour of preparation, and the hydrolysis half-life is on the order of weeks [12],the former explanation seems unlikely. Since the peak intensities did not change during these measurements, photo-degradation catalyzed by silver also seems unlikely. Further experiments are required to clarify this point.The SER spectrum of the other hydrolysis product formed from VX, EMPA, is shown in Figure 25.6. It is includedwith MPA and IMPA, the hydrolysis products of GB, for convenient spectral comparison of these structurallysimilar chemicals. The spectrum is dominated by a peak at 745 cm-1 with a substantial low frequency shoulder at725 cm-1. Both are assigned, similarly to IMPA, to PC or PO plus skeletal stretching modes. In fact, virtually all ofthe peaks in the SER spectrum correspond to peaks of similar frequency in the SER spectrum of IMPA, and areassigned as follows: the peaks at 480 and 500 cm-1 to PC or PO plus skeletal bends; 890, 1415, and 1440 cm-1 toCHn deformations; 945 and 1060 cm-1 to POn stretches; and 1095 to a CO or CC stretch. A peak at 1285 cm-1 isassigned to a CHn deformation based on the MPA spectral assignment for a peak at 1300 cm-1.In this series of chemicals VX and EA2192 were routinely measured at 100 mg L-1, and on occasion at 10 mg L-1using the SERS-active vials. Again, however, only a limited number of measurements were attempted. More
  • Springer Book Kneipp Editor Draft 10extensive measurements of EMPA using the SERS-active capillaries allowed repeatable measurements of 10 mg L-1and routine measurements of 1 mg L-1. No concentration studies of DIASH were undertaken.25.4 ConclusionsThe ability to obtain surface-enhanced Raman spectra of several chemical agents and their hydrolysis products hasbeen demonstrated using silver-doped sol-gels. Two sampling devices, SERS-active vials and capillaries, provideda simple means to measure water samples containing chemical agents. No sample pretreatment was required and allspectra were obtained in 1 minute. It was found that the SER spectra can be used to identify chemical agents byclass. Specifically, cyanide contains a unique peak at 2100 cm-1, HD and CEES both have a unique peak at 630cm-1, while VX has a unique peak at 540 cm-1. In the case of HD and CEES, their hydrolysis products produce verysimilar spectra, and it may be difficult to determine relative concentrations in an aqueous solution. In the case of theVX hydrolysis products, EA2192 and DIASH were spectrally similar, as was IMPA and MPA. However, thereappears to be sufficient differences when comparing entire spectra, such that chemometric approaches might allowsuccessful compositional analysis of aqueous solutions.The SERS-active vials and capillaries provided sufficient sensitivity to measure cyanide below the required 2 mg L-1sensitivity either as a point measurement or as a continuous flowing stream measurement. Measurements of TDGsuggest that the sensitivity requirements for it and HD may be attainable with modest improvements. In contrast,the vials and capillaries did not provide sensitivity sufficient to meet the requirements of VX. In this casesubstantial improvements in sensitivity are required and are being pursued.25.5 AcknowledgementsThe authors are grateful for the support of the U.S. Army (DAAD13-02-C-0015, Joint Service Agent Water Monitorprogram) and the Environmental Protection Agency (EP-D-05-034). The authors would also like to thank Mr.Chetan Shende for sol-gel chemistry development.25.6 References1 S.L. Hoenig: Handbook of Chemical Warfare and Terrorism. (Greenwood Press, 2002) p. 8, 19, 34-632 H. Nozaki, N. Aikawa: Sarin poisoning in Tokyo subway. Lancet 345, 1446 (1995)3 Committee on Toxicology: Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents. (Nat Acad Press, 1997)4 Committee on Toxicology: Guidelines for Chemical Warfare Agents in Military Field Drinking Water. (Nat Acad Press, 1995)5 T.C. Marrs, R.L. Maynard, F.R. Sidell: Chemical Warfare Agents: Toxicology and Treatment. (John Wiley and Sons, 1996)6 Material Safety Data Sheets, available at www.msds.com7 D.R. Lide, Ed: Handbook of Chemistry and Physics: (CRC Press, 1997) p. 8-438 N.B. Munro, S.S. Talmage, G.D.Griffin, L.C. Waters, A.P. Watson, J.F. King, V. Hauschild: Environ. Health Perspect. 107, 933 (1999)9 A.G. Ogsten, E.R. Holiday, J.St.L.Philpot, L.A. Stocken: Trans. Faraday Soc. 44,45 (1948)10 G. Wagner, Y. Yang: Ind. Eng. Chem. Res. 41, 1925 (2002)11 W. Creasy, M. Brickhouse, K. Morrissey, J. Stuff, R. Cheicante, J. Ruth, J. Mays, B. Williams, R. O’Connor, H. Durst: Environ. Sci. Technol. 33, 2157 (1999)12 Y. Yang: Acc. Chem. Res. 32, 109 (1999)13 Y. Yang, J. Baker, J. Ward: Chem. Rev. 92, 1729 (1992)14 B. Erickson: Anal. Chem. News & Features, 397A (1998)15 Product literature at http://www.wmdetect.com/Library/M8/M8%20Paper.htm16 R.M. Black, R.J. Clarke, R.W. Read, M.T. Reid: J. Chromat. 662, 301 (1994)17 G.A. Sega, B.A. Tomkins, W.H. Griest: J Chromat. A 790, 143 (1997)18 S.A. Oehrle, P.C. Bossle: J. Chromat. A 692, 247 (1995)19 J.E. Melanson, B.L-Y. Wong, C.A. Boulet, C.A. Lucy: J. Chromat. A 920, 359 (2001)20 J. Wang, M. Pumera, G.E. Collins, A. Mulchandani: Anal. Chem. 74, 6121 (2002)
  • Springer Book Kneipp Editor Draft 1121 W.R. Creasy: Am. Soc. Mass. Spectrom. 10, 440 (1999)22 Q. Liu, X. Hu, J. Xie: Anal. Chim. Acta 512, 93 (2004)23 G.A. Eiceman, Z. Caras: Ion Mobility Spectrometry. (CRC Press, 1994)24 See products from Smiths Detection, Bruker Daltronics, etc.25 N. Krylova, E. Krylov, G.A. Eiceman: J. Phys. Chem. 107, 3648 (2003)26 W.E. Steiner, B.H. Clowers, L.M. Matz,W.F. Siems, H.H. Hill Jr.: Anal. Chem. 74, 4343 (2002)27 L.D. Hoffland, R.J. Piffath, J.B. Bouck: Opt. Eng. 24, 982 (1985)28 S.D. Christesen: Appl. Spectrosc. 42, 318 (1988)29 E.H.J. Braue, M.G. Pannella: Appl. Spectrosc. 44, 1513 (1990)30 C-H. Tseng, C.K. Mann, T.J. Vickers: Appl. Spectrosc. 47, 1767 (1993)31 S. Kanan, C. Tripp: Langmuir 17: 2213 (2001)32 D.L. Jeanmaire, R.P. Van Duyne: J. Electroanal. Chem. 84, 1 (1977)33 A.M. Alak, T. Vo-Dinh: Anal. Chem. 59, 2149 (1987)34 K.M. Spencer, J. Sylvia, S. Clauson, J. Janni: Proc. SPIE 4577,158 (2001)35 S.D. Christesen, M.J. Lochner, M. Ellzy, K.M. Spencer, J. Sylvia, S. Clauson: 23rd Army Sci. Conf. (2002)36 S.D. Christesen, K.M. Spencer, S. Farquharson, F.E. Inscore, K. Gosner, J. Guicheteau: In: S. Farquharson, Ed. Applications of Surface-Enhanced Raman Spectroscopy. (CRC Press, in preparation)37 P. Tessier, S. Christesen, K. Ong, E. Clemente, A. Lenhoff, E. Kaler, O. Velev: Appl. Spectrosc. 56, 1524 (2002)38 Y. Lee, S. Farquharson: Proc. SPIE 4378, 21 (2001)39 S. Farquharson, P. Maksymiuk, K. Ong, S. Christesen: Proc. SPIE 4577, 166 (2001)40 S. Farquharson, A. Gift, P. Maksymiuk, F. Inscore, W. Smith, K. Morrisey, S. Christesen: Proc. SPIE 5269, 16 (2004)41 S. Farquharson, A. Gift, P. Maksymiuk, F. Inscore, W. Smith: Proc. SPIE 5269, 117 (2004)42 F. Inscore, A. Gift, P. Maksymiuk, S. Farquharson: Proc. SPIE 5585, 46 (2004)43 S. Farquharson, A. Gift, P. Maksymiuk, F. Inscore: Appl. Spectrosc. 59, 654 (2005)44 S. Farquharson, P. Maksymiuk: Appl. Spectrosc. 57, 479 (2003)45 S. Farquharson, Y.H. Lee, C. Nelson: U.S. Patent Number 6,623,977 (2003)46 S. Farquharson, P. Maksymiuk: U.S. Patent Numbers 6,943,031 and 6,943,032 (2005)47 S. Farquharson, A. Gift, P. Maksymiuk, F. Inscore: Appl. Spectrosc. 58, 351 (2004)48 F. Inscore, A. Gift, P. Maksymiuk, J. Sperry, S. Farquharson: In: S. Farquharson, Ed. Applications of Surface- Enhanced Raman Spectroscopy. (CRC press, in preparation)49 D. Kellogg, J. Pemberton: J. Phys. Chem. 91, 1120 (1987)50 J. Billmann, G. Kovacs, A. Otto: Surf. Sci. 92,153 (1980)51 C.A. Murray, S. Bodoff: Phys. Rev. B 32,671 (1985)52 S.D. Christesen: J. Raman Spectrosc. 22, 459 (1991)53 C. Sosa, R.J. Bartlett, K. KuBulat, W.B. Person: J. Phys. Chem. 93, 577 (1993)54 F. Inscore, S. Farquharson: J. Raman Spectrosc. (submitted)55 F. Inscore, S. Farquharson: Proc. SPIE 5993, accepted (2005)56 T. Joo, K. Kim, M. Kim: J. Molec. Struct. 16, 191 (1987)57 H. Hameka, J. Jensen: CRDEC-TR-326 (1992)58 R. Nyquist: J. Molec. Struct. 2:123 (1968)59 B.J. Van der Veken, M.A. Herman: J. Molec. Struct. 15, 225 (1973)60 B.J. Van der Veken, M.A. Herman: J. Molec. Struct. 15, 237 (1973)61 H. Hameka, J. Jensen: ERDEC-TR-065 (1993)
  • Appendix N Detecting hydrolysis products of blister agents in water by surface-enhanced Raman spectroscopy Frank Inscore and Stuart Farquharson Real-Time Analyzers, Middletown, CT, 06457 ABSTRACTProtecting the nation’s drinking water from terrorism, requires microg/L detection of chemical agents and theirhydrolysis products in less than 10 minutes. In an effort to aid military personnel and the public at large, we have beeninvestigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect microgram per liter (part-per-billion)concentrations of chemical agents in water. It is equally important to detect and distinguish the hydrolysis products ofthese agents to eliminate false-positive responses and evaluate the extent of an attack. Previously, we reported the SERspectra of GA, GB, VX and most of their hydrolysis products. Here we extend these studies to include the chemicalagent sulfur-mustard, also known as HD, and its principle hydrolysis product thiodiglycol. We also report initialcontinuous measurements of thiodiglycol flowing through a SERS-active capillary.Keywords: chemical warfare agent detection, CWA, hydrolysis, SERS, Raman spectroscopy 1. INTRODUCTIONThe July 2005 terrorist bombings of the London transit system are a stark reminder that such attacks on the UnitedKingdom and the United States will continue. Countering such attacks requires recognizing likely deployment scenariosand having the required technology to rapidly detect the deployment event. In addition to the expected use of chemicalagents released into the air, terrorists may also poison water supplies with chemical warfare agents (CWAs). TheNational Strategy for Homeland Security designates the Environmental Protection Agency with the task of securing thenations drinking water.1 Presently, the EPA employs several field test kits to monitor drinking water supplies, and gaschromatography coupled with mass spectrometry in supporting laboratories to confirm positive responses.2Unfortunately, these test kits are prone to false-positive responses, and follow-up analysis typically takes a day. This isentirely inadequate for the prevention of widespread illness and potential fatalities.In the past several years we have been investigating the use of surface-enhanced Raman spectroscopy (SERS) to be usedas a field-usable analyzer that can detect chemical agents in water at the required microg/L sensitivity and 10 minutetimeframe.3,4,5,6,7 The expected success of SERS is based on the million-fold or more Raman signal increase obtainedwhen a molecule interacts with surface plasmon modes of metal nanoparticles.8 In the case of cyanide, an industrial-based CWA and methyl phosphonic acid, the final hydrolysis product for the nerve agents, we have measured at orbelow 10 microg/L in one minute.9 The expected success of SERS is also based on the unique set of Raman spectralpeaks associated with the molecular vibrational modes of each molecule. The unique SER spectra should not onlyreduce false-positive responses, but also allow discriminating hydrolysis products of CWAs. This is important, sinceCWAs can hydrolyze rapidly in the presence of water,10 and detection of the hydrolysis products could allowdetermining 1) the state of an attack (ratio of CWA to hydrolysis product(s)), 2) the point of attack initiation, and 3) thecontinued extent and severity of the CWA attack throughout a water distribution system.Previously, we used SERS to measure sarin, tabun, VX, and EA2192, and their respective hydrolysis products.3,4,6,7 Herewe extend these studies to include the chemical warfare agent sulfur-mustard, designated HD, and its primary hydrolysisproduct thiodiglycol (TDG, Figure 1). The physical and chemical properties of this blister agent are well known. It’ssolubility in water is 0.92 g/L with a hydrolysis half-life of 8.5 min (both at 25 C).10 HD has an oral LD50 of 0.7 mg/kgin humans,11 and the military drinking water guideline places the 5-day 5L limit at 100 microg/L.12 TDG is relativelynon-toxic, very water soluble at 690 g/L, and stable in water with a hydrolysis half-life of approximately 6 days.Accordingly, a reasonable sensitivity goal to ensure safe water is placed at 10 microg/L for HD and an equivalent goal tomap HD usage is placed at 10 microg/L for TDG.13 SPIE-2005-5993 19
  • H2O + 2HClFigure 1. Hydrolysis of bis(2-chloroethyl)sulfide (HD) to bis(2-hydroxyethyl)sulfide (TDG). 2. EXPERIMENTALHighly distilled sulfur mustard, designated HD (bis(2-chloroethyl)sulfide), was measured at the U.S. Army’s EdgewoodChemical Biological Center (Aberdeen, MD). Thiodiglycol, designated TDG here (bis(2-hydroxyethyl)sulfide), waspurchased as an analytical reference material from Cerilliant (Round Rock, TX). TDG was measured at Real-TimeAnalyzers, Inc. (RTA, Middletown, CT). All solvents, including methanol, ethanol, and HPLC water, as well as all sol-gel precursor chemicals including AgNO3, tetramethyl orthosilicate, methyltrimethoxysilane, HNO3 and NaBH4, werepurchased from Sigma-Aldrich (St. Louis, MO). HD samples prepared for SERS analysis consisted of 0.1% v/v HD inmethanol. The methanol was used to minimize hydrolysis. The final concentration is 1000 parts-per-million (ppm, EPAdefinition). TDG samples were prepared for SERS analysis using methanol for static measurements and HPLC gradewater for flow measurements. All HD measurements were performed in SERS-active vials (Simple SERS Sample Vials,RTA),14 while all TDG measurements were performed in SERS-active capillaries (1-mm diameter glass capillaries filledwith silver-doped sol-gels).15,16 In the case of flow measurements, a peristaltic pump (variable flow mini-pump, ControlCo., Friendswood, TX) was used to flow the 1 and 10 ppm TDG samples through a SERS-active capillary at 1 mL permin.The vials or capillaries were mounted horizontally on an XY positioning stage (Conix Research, Springfield, OR), suchthat the focal point of an f/0.7 aspheric lens was positioned just inside the glass wall. The probe optics and fiber opticinterface have been described previously.16 In all cases a 785 nm diode laser was used to deliver ~100 mW of power tothe SERS samples and 300 mW to the Raman samples. A Fourier transform Raman spectrometer equipped with asilicon photo-avalanche detector (RTA, model IRA-785), was used to collect both the RS and SERS at 8 cm-1 resolution. 3. RESULTS AND DISCUSSIONThe surface-enhanced and normal Raman spectra of HD have been measured and are shown in Figure 2. The SERspectrum is dominated by a peak at 630 cm-1 with an extended high frequency shoulder composed of two or more peaks(695, 830 cm-1), as well as a moderately intense peak at 1045 cm-1. It is possible to assign these peaks based on thenormal Raman spectrum of HD, and previous assignments.17 Theoretical studies assigned the 640, 655, 700 cm-1 peaksto C-Cl stretching modes and the 740, and 760 cm-1 peaks to C-S stretching modes. Additional peaks are observed at1040, 1190, 1270, 1295, 1410, 1425, and 1440 cm-1. The first peak is assigned to a C-C stretch, while the remainingpeaks are all CH2 deformation modes (scissors, twists, and wags). Based on these assignments, then only the C-Cl peakmaintains significant intensity in the SER spectrum occurring at 630 cm-1. If the C-Cl assignments are correct, then theSER spectra suggest that the molecule to metal interaction is strongest through the chlorine end groups. Alternatively,the electron lone pairs of the tetrahedrally coordinated sulfur of HD could interact with the silver surface. Consequently,the 630 cm-1 SERS peak could be assigned to CS or CSC stretching modes (see below).18The surface-enhanced and normal Raman spectra of TDG have been measured and are shown in Figure 3. The SERspectrum is dominated by three peaks at 630, 715, and 1010 cm-1 with minor peaks at 400, 820, 930, 1210, 1275, 1410,and 1460 cm-1. Similarly, the Raman spectrum contains two intense peaks at 660 and 1010 cm-1, while moderatelyintense peaks occur at 400, 680 (shoulder), 735, 770, 830, 950, 1040, 1230, 1290, 1420, and 1465 cm-1. In both spectra,the assignment of the peaks near 1000 cm-1 can be confidently assigned to C-C stretching modes, while the peaks from1200 to 1465 cm-1 can be confidently assigned to various CH2 deformation modes. Here, however, it is difficult toassign the 630 cm-1 SERS peak to a C-Cl mode, since the chlorines have been replaced by hydroxyl groups. SPIE-2005-5993 20
  • Consequently, in the case of HD and TDG, assigning the 630 cm-1 peak to a CS or a CSC stretch, is favored. Althoughthe 620-680 cm-1 peaks are normally assigned to C-Cl modes, and the 700-750 cm-1 peaks to CS modes, most authorsconcede that the reverse assignments are possible. A A B BFigure 2. A) SERS and B) RS of HD. A) 0.1% v/v (1000 Figure 3. A) SERS and B) RS of TDG. A) 0.1% v/v inppm) in MeOH in a SERS-active vial, 100 mW of 785 nm, MeOH in SERS-active capillary, 100 mW of 785 nm, 1-1-min, B) neat sol. in glass container, 300 mW of 785 nm, min, B) neat sol. in glass capillary, 300 mW of 785 nm,5-min. 5-min.Of possibly greater importance, is that the TDG SER spectrum is of high quality, with three distinct peaks. With thegoal of detecting this hydrolysis product of HD in water, a number of samples of decreasing concentration were preparedand measured. As Figure 4 shows, these peaks are evident even at 10 ppm (0.001% v/v in methanol). However,repeated measurements of 1 ppm did not yield any discernable peaks (lowest trace in Figure 4). Notwithstanding,measurements were also performed in a flowing stream. Initial measurements of a 10 ppm sample yielded qualityspectra and prompted measurements of a 1 ppm sample. As Figure 5 shows, reasonable spectra are obtained, even at 1minute resolution. It is worth stating that the 630 cm-1 peak was evident in all spectra collected over a 12 minute period.There is an important difference between the TDG spectra recorded for static and flowing samples, namely that the 715cm-1 peak is noticeably more intense in the static sample. This suggests that it may represent a photo-degradationproduct. Further studies are required to clarify this point. Figure 4. SERS of 1000, 100, 10 and 1 ppm TDG in Figure 5. SERS of 1 ppm TDG in water flowing water (top to bottom). All in SERS-active capillaries, through a SERS-active capillary at 1, 2, 3, 4, and 5 min. 100 mW of 785 nm, 1-min. (top to bottom), 100 mW of 785 nm, 1-min each. SPIE-2005-5993 21
  • 4. CONCLUSIONSThe ability to measure and distinguish HD and TDG using SERS-active capillaries has been demonstrated. Specifically,the peak at 715 cm-1 is unique to TDG, as both chemicals produce an intense SERS peak at 630 cm-1. The latter peak islikely due to CS or CSC stretching modes favorably enhanced by the interaction of the sulfur lone electron pairs to silversurface. Measurements of similar chemicals, such as diethylsulfide, are ongoing to clarify this assignment. Detection ofTDG at 1 mg/L in 1 minute in a flowing system suggests that the goal of 10 microg/L in 10 minutes is possible.Improvements in the enhancement achieved by the SERS-active capillaries, as well as their durability, are the focus ofcurrent research and product development. 5. ACKNOWLEDGMENTSThe authors are grateful for the support of the U.S. Army (DAAD13-02-C-0015, Joint Service Agent Water Monitorprogram) and the Environmental Protection Agency (EP-D-05-034). The authors would also like to thank Dr. SteveChristesen for helpful discussions, and Mr. Chetan Shende for sol-gel chemistry development. 6. REFERENCES1 Whitman, CT, “EPA’s Strategic Plan for Homeland Security”, 2002, available at http://www.epa.gov/epahome/downloads/epa_homeland_security_strategic_plan.pdf2 Creasy, W., Brickhouse, M., Morrissey, K., Stuff, J., Cheicante, R., Ruth, J., Mays, J., Williams, B., O’Connor, R., Durst, H., “Analysis of chemical weapons decontamination waste from old ton containers from Johnston atoll using multiple analytical methods”, Environ. Sci. Technol., 33, 2157-2162, (1999).3 Farquharson, S., Maksymiuk, P., Ong, K., Christesen, S., “Chemical agent identification by surface-enhanced Raman spectroscopy”, SPIE, 4577, 166-173 (2001).4 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., Smith, W., Morrisey, K., Christesen, S., “Chemical agent detection by surface-enhanced Raman spectroscopy”, SPIE, 5269, 16-22 (2004).5 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., Smith, W., “pH dependence of methyl phosphonic acid, dipicolinic acid, and cyanide by surface-enhanced Raman spectroscopy”, SPIE, 5269, 117-125 (2004).6 Inscore, F., A. Gift, P. Maksymiuk, S. Farquharson, “Characterization of chemical warfare G-agent hydrolysis products by surface-enhanced Raman spectroscopy” SPIE, 5585, 46-52 (2004).7 Farquharson, S., A. Gift, P. Maksymiuk, F. Inscore “Surface-enhanced Raman spectra of VX and its hydrolysis products”, Appl. Spectrosc., 59, 654-660 (2005).8 Jeanmaire, D.L., and R.P. Van Duyne, J. Electroanal. Chem., 84, 1-20 (1977).9 Inscore, F., P. Maksymiuk, and S. Farquharson, “SERS detection of chemical agents in flowing streams”, in preparation.10 Munro, N.B., Talmage, S.S., Griffin, G.D., Waters, L.C., Watson, A.P., King, J.F., and Hauschild V. “The Sources, Fate, and Toxicity of Chemical Warfare Agent Degradation Products”, Environ. Health Perspect. 107, 933-974 (1999).11 Committee on Toxicology, Review of Acute Human-Toxicity Estimates for Selected Chemical-Warfare Agents, Nat. Acad. Press (Washington, D.C.) 199712 Hauschild, V. et al. “Short-Term Exposure Guidelines for Deployed Military Personnel”, USACPPM TG 230A (May, 1999) available at http://chppm-www.apgea.army.mil/imo/ddb/dmd/DMD/TG/TECHGUID/Tg230.pdf13 These values are only estimates made by the authors.14 Farquharson, S., Y.H. Lee, and C. Nelson, “Material for surface-enhanced Raman spectroscopy and SER sensors, and method for preparing same", U.S. Patent Number 6,623,977 (2003)15 Farquharson, S. and P. Maksymiuk “Simultaneous chemical separation and surface-enhanced Raman spectral detection using metal-doped sol-gels” and “Separation and Plural-point surface-enhanced Raman spectral detection using metal-doped sol-gels”, U.S. Patent Numbers 6,943,031 and 6,943,032 (2005)16 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., “Rapid dipicolinic acid extraction from Bacillus spores detected by surface-enhanced Raman spectroscopy”, Appl. Spectrosc. 58, 351-354 (2004).17 Sosa, C., R.J. Bartlett, K. KuBulat, and W.B. Person, “A theoretical study of harmonic vibrational frequencies and infrared intensities of XCH2CH2SCH2CH2X and XCH2CH2SH (= H, Cl)”, J. Phys. Chem., 93, 577-588 (1993).18 Joo, T., K. Kim, M. Kim “Surface-enhanced Raman study of organic sulfides adsorbed on silver”, J. Molec. Struct.,16, 191-200 (1987). SPIE-2005-5993 22
  • Paper in preparation Appendix O 1Surface-enhanced Raman spectroscopic characterization of the chemical warfare agent vesicant HD and related mono-sulfides Frank Inscore, Paul Maksymiuk and Stuart Farquharson* Real-Time Analyzers, Middletown, CT, 06457ABSTRACTSurface-enhanced Raman spectroscopy (SERS) is a useful technique for detecting extremely low concentrations (e.g. part-per-billion) of chemical agents, as might be found in poisoned water supplies. Since trace quantities of nerve agents (VXand G-series) and blister agents (mustard) can be hydrolyzed in the presence of water, it is important to characterize thedegradation products. We have previously demonstrated the ability of SERS to detect the primary hydrolysis products ofVX, and of GB, GD and GF. This present study is focused on the vesicant mustard (HD) and its primary hydrolysisproducts thiodiglycol and related mono-sulfides. Our SERS-active medium consists of silver or gold nanoparticlesincorporated into a sol-gel matrix, which is immobilized in a glass capillary. The choice of sol-gel precursor allowscontrolling hydrophobicity, while the porous silica network offers a unique environment for stabilizing the SERS-activemetals. Here we present the use of these metal-doped sol-gels to selectively enhance the Raman signal of mustard andrelated hydrolysis products.Keywords: chemical warfare agent detection, CWA, hydrolysis, SERS, Raman spectroscopy 1. INTRODUCTIONThe potential use of chemical and biological warfare agents by terrorist organizations directed against U.S. military andCoalition forces in the Middle East, and civilians at home, is an issue that has generated considerable concern in the post9/11 era. The ability to counter such attacks, requires recognizing likely deployment scenarios, among which includes thedistribution of chemical warfare agents (CWAs) through water supplies. In response to this threat we and others haveemployed surface-enhanced Raman spectroscopy to measure extremely lethal nerve agents such as VX and EA2192, aswell as HD (a representative vesicant).1,2,3,4,5,6,7 Since CWAs can hydrolyze rapidly in the presence of water8,9,10,11 we havealso measured the primary hydrolysis products of VX,12 and of the G-series of nerve agents13 with our SERS-active sol-gelcoated capillaries. The utility of SERS derives from the extreme sensitivity of this technique afforded by the interaction ofsurface plasmon modes of metal particles with target analytes,14 the ability to quantitate species in water without spectralinterference, and to identify molecular structure through the abundant vibrational information provided by Ramanspectroscopy.15 In a continued effort to characterize CWAs in water, we now present the SERS of mustard HD and of otherrelated sulfur complexes including primary hydrolysis products.The physical and chemical properties of the vesicant Bis(2-chloroethyl)sulfide, designated HD for the ultra-pure distilledform of the blistering agent known as sulfur-mustard, are well known, and are certainly different in many aspects than thoseof the more lethal nerve agents. HD has an oral LD50 of 0.7 mg/kg in humans, and is not very soluble in water (Table 1)due to an inherently slow dissolution rate. However, once dissolution of HD occurs, the rate of hydrolysis is very rapid(Figure 1), with formation of thiodiglycol (TDG) as the primary product through a sulfonium intermediate. Althoughconsiderably less toxic than HD, this relatively more stable hydrolysis product is also a major precursor for the industrialpreparation of sulfur mustard, and as a result the use and availability of the TDG sulfide complex is monitored and has beenclassified by the Chemical Weapons Convention (CWC) as a Schedule 2B chemical. TDG, which has greater solubility inwater than HD, can be oxidized in the presence of air to thiodiglycol sulfoxide (TDG-SO). Furthermore, under certainconditions TDG can react with HD, the sulfonium intermediate or Hemi-mustard (2-chloroethyl 2-hydroxyethyl)sulfide toform secondary degradation products.Table 1. Properties of sulfur-mustard and primary hydrolysis products investigated in the present study. Chemical Agent Hydrolysis ½ life a Water Solubility b @25°C Mustard (HD) 8.5 min @25°C distilled water 0.92 g/L TDG stable ~6 weeks (can oxidize to TDG-SO) 690 g/L TDG-SO stable miscibleTDG = thiodiglycol, TDG-SO = thiodiglycol sulfoxide. a from Reference 10, b from Reference 11. Note the JSAWM required detectionlimit of HD in water is 3 mg/L in less than 10 minutes. 1
  • Paper in preparation 2 O H 2O [Ox] TDG-SO TDGHD 2 HCl + S S S HO OH HO OH Cl ClFigure 1. Primary Hydrolysis pathway of HD: degradation products shown in their protonated forms.The ability to detect and characterize the more persistent hydrolysis products of HD such as TDG is important for a numberof reasons: 1) they are indicators for identifying the parent CWA present (or provide strong supporting evidence for prioruse of), 2) for assessing if degradation of the CWA has occurred, and 3) they provide a means for predicting when the watersupply was poisoned. 2. EXPERIMENTALThe CWA vesicant Bis(2-chloroethyl)sulfide (designated HD or distilled sulfur mustard) was supplied as a neat liquid bythe U.S. Army at the Edgewood Chemical Biological Center (Aberdeen, MD). All Raman and SERS measurementsinvolving HD were acquired at this facility, while the other chemicals presented here were measured at Real-TimeAnalyzers (RTA, Middletown, CT). The primary HD hydrolysis product Bis(2-hydroxyethyl)sulfide (designated TDG orthiodiglycol) and subsequent oxidation product Bis(2-hydroxyethyl)sulfoxide (designated TDG-SO or thiodiglycolsulfoxide) were purchased as analytical reference materials from Cerilliant (Round Rock, TX). TDG was purchased as aneat liquid. Although the pure liquid form of TDG-SO was available, it was purchased here in forensic quantities (1mg/mL in MeOH). The additional mono-sulfides studied, which included dimethyl sulfide (MMS), diethyl sulfide (EES),2-hydroxyethyl ethylsulfide (HEES), 2-chloroethyl ethylsulfide (CEES), 2-chloroethyl methylsulfide (CEMS), and 2-chloroethyl phenylsulfide (CEPS), were obtained as neat liquids at the highest purity available from Sigma-Aldrich (St.Louis, MO) and used here without further purification. The other chemicals purchased, which include the additional testanalytes ethanethiol (EtSH), 2-hydroxy ethanethiol (HOEtSH) and 3-chloro propanethiol (ClPrSH) as neat liquids, andthose chemical reagents and solvents used to prepare the silver-doped and gold-doped sol-gels, were also acquired fromSigma-Aldrich (St. Louis, MO) and used as received. All solvents, including those used for sample preparation were ofHPLC grade. For safety purposes, all samples were prepared and manipulated in a chemical hood, where they wereintroduced to the sampling device and sealed before being measured. Prior to the SERS studies, Raman spectra (RS) of thedi-alkyl- and alkyl-aromatic-sulfides, and the other relevant structural fragments (including thiols and alcohols) weremeasured in capillaries as pure liquids with the exception of TDG-SO (1 mg purchased in a 1mL methanol solution). TheRaman spectrum of ethane thiolate (deprotonated form of EtSH in 1N KOH) was also measured. In the case of surface-enhanced Raman spectral measurements, the sulfides MMS, EES, HEES, CEES, CEMS, CEPS, and TDG were preparedinitially as 1% v/v solutions in methanol (10 mg/mL), as were the thiols EtSH, HOEtSH, and ClPrSH. Samples at lowerconcentrations were prepared by sequential serial dilution of the stock analyte solution using the appropriate solvent. The1mg/mL forensic sample of TDG-SO (0.1% v/v in methanol) was tested as received. In some cases, the test analyte wasdirectly prepared in water at the desired concentration level. All solutions were immediately measured following theirpreparation in order to obtain a base-line spectral reference, with subsequent measurements made over time to determinewhether or not the integrity of the sample had been compromised by potential degradation processes. Samples of HD weretested initially in a water/isopropanol mixture (pre-dissolved in the alcohol and volumetrically brought to the desiredconcentration with water prior to measurements). The SERS-response of HD was also measured in pure methanol. In bothcases the SERS of HD was measured at Aberdeen in 2-mL glass vials internally coated with a layer of silver-doped or gold-doped sol-gel (Simple SERS Sample Vials, Real-Time Analyzers, East Hartford, CT), while the other chemicals weremeasured at RTA in a series of 1-mm diameter glass capillaries filled with a pre-defined library subset of chemicallyselective silver and gold doped sol-gels. CEMS, CEES, CEPS, and TDG were also measured at RTA in vials spin-coatedwith the standard silver-doped sol-gel chemistry that were similar to those used in the previous HD SERS studies.3 Thecapillaries were prepared according to previously published methods, where the silver doped sol-gel chemistry used asilver-amine intermediate formed from the addition of excess ammonium hydroxide to AgNO3.16 However, a combinationof different Si-alkoxides including tetramethyl orthosilicate (TMOS), methyltrimethoxysilane (MTMS), andoctadecyltrimethoxysilane (ODS) were employed instead of plain TMOS. The following four chemically selective silver-doped sol-gel libraries for coating capillaries designated TMOS/MTMS (1:6 v/v), MTMS, MTMS/ODS/TMOS (5:1:1v/v/v) and MTMS/ODS (10:1 v/v) with analyte selectivity ranging from polar-negative to non-polar-negative were usedhere in this study to screen the chemicals for SERS-activity. The gold-doped sol-gel chemistry employed HAuCl4 in nitricacid with pure TMOS or a mixture of TMOS/MTMS. For both the silver and gold chemistries, fresh dilute NaBH4(0.1g/100ml HPLC water, pH=9.65 @23°C) was used to reduce the sol-gels after an appropriate curing period (generally24 hrs), followed by a water wash to remove residual reducing agent. Additional treatment of the sol-gels with various acidwashes using HNO3 and or HCl at different concentrations provided a means to affect analyte selectivity and or increasesensitivity. 2
  • Paper in preparation 3Both sampling configurations (vials and capillaries) were mounted horizontally on an XY positioning stage (ConixResearch, Springfield, OR), such that the focal point of an f/0.7 aspheric lens was positioned just inside the glass wall. Theprobe optics and fiber optic interface have been described previously.16 In all cases a 785 nm diode laser (ProcessInstruments Inc. model 785-600, Salt Lake City, UT) was used to deliver ~100 mW of power to the SERS samples and 100to 300 mW to the Raman samples. A Fourier transform Raman spectrometer (Real-Time Analyzers, model IRA-785, EastHartford, CT), and a silicon photo-avalanche detector (Perkin Elmer model C30902S, Stamford, CT) was used to collectboth the RS and SERS at 8 cm-1 resolution and at 5-min and 1-min acquisition times, respectively, except in the case of theRS of neat HD. This measurement, performed at Aberdeen, used a 785 nm diode laser to deliver 100 to 150 mW to thesample. A dispersive spectrometer and silicon-based CCD detector were used to acquire 1 cm-1 resolution spectra in 1-minacquisitions (InPhotonics, Norwood, MA).17 The SERS of HD samples prepared fresh in methanol at 1.152 and 0.1152mg/mL concentration levels were also measured recently at Aberdeen in the silver coated sol-gel vials using this CCD-based 785nm dispersive Raman system (60 sec and 100 mW). 3. RESULTS AND DISCUSSIONThe assignment of observed peaks in the surface-enhanced Raman spectra of the vesicant HD and related mono-sulfides arein general anticipated to be more complicated relative to their normal Raman spectral counterparts as a result of metal-to-molecule surface interactions, which can shift and enhance various vibrational modes to different extents. Such surfaceinteractions and subsequent enhancement of specific vibrational modes are dependent upon numerous conditions andparameters, which include the nature of the metal substrate and analyte functional groups involved, and how the adsorbedmolecule is oriented with respect to the surface.18,19 Therefore, in order to aid in the interpretation of the SERS, thecorresponding Raman spectrum for each of the chemicals investigated in this study was also measured and included in thespectral analysis. The observed Raman peaks are assigned to vibrational modes visualized in Gauss-View using resultsobtained from density functional calculations performed on the optimized structures (DFT 6-31** with B3LPY, Gaussian03, Wallingford, CT), and assignments that have been previously reported.Additional factors that must be considered in the analysis of HD SERS include degradation as a result of hydrolysis (oroxidation) in water, combined with the potential of metal surface interactions to induce such processes. In addition,sulfides are well known to be photo-reactive on silver (and gold) in that they can form thiolate fragments due to C-S bondcleavage, which subsequently can adsorb to the metal surface.20,21,22,23,24 To further aid in the spectral assignment of HDand to assess the electronic effects of Cl coordination and OH substitution during hydrolysis, a series of mono-sulfides wasexamined with the basic skeletal structure XCH2CH2SCH2CH2X (where X = H, OH, Cl). The Raman and SERS spectra ofthese aliphatic mono-sulfides including EES (HCH2CH2SCH2CH2H), HEES (HCH2CH2SCH2CH2OH), TDG(HOCH2CH2SCH2CH2OH), CEES (HCH2CH2SCH2CH2Cl) and HD (ClCH2CH2SCH2CH2Cl), in addition to several simplemolecular fragments that comprise the skeletal structure of the parent complexes are presented in Figures 1-4 forcomparative purposes. The RS and SERS of this series of sulfide complexes are shown in Figures 2 and 4 respectively.The RS and SERS of the thiol complexes (EtSH, HOEtSH, and ClPrSH) shown in Figures 3 and 5 not only provide aninitial basis for understanding the vibrational spectra of the sulfides and how they interact with the metal surface, but alsoserve as a means for determining if the parent sulfide complex has photo-degraded via scission of the C-S bond uponadsorption and or subsequent irradiation. Although hemi-mustard (ClCH2CH2SCH2CH2OH) is a direct product of HDhydrolysis, albeit a relatively short-lived intermediate that subsequently hydrolyzes to form TDG, and represents anadditional perturbation that would have completed this series, it unfortunately was not available for study at this time.Similarly, 2-chloro-ethanethiol, which represents the primary photo-degradation product of HD (and {CES} complexes ingeneral) resulting from possible C-S cleavage was also not commercially available. However, 3-chloro-propanethiol(ClPrSH) was obtained, and the behavior of Cl on this extended aliphatic thiol was examined instead. Additionaldegradation fragments resulting from the potential cleavage of the C-S bond in the aliphatic mono-sulfides investigated inthis study, which include ethane, 2-chloroethane or 2-hydroxyethane (ethanol) are not anticipated to be SERS-active, and asa result should not be problematic in the SERS analysis. To minimize potential degradation, the initial SERSmeasurements were carried out on fresh pristine samples prepared in methanol with limited exposure to air and water, atlow laser powers (25-100 mW) and short acquisition times (20-60 sec), as well as at excitation wavelengths that areelectronically decoupled from the analyte adsorbed on the metal surface (785 nm and 1064 nm).The dominant vibrational peaks observed in the Raman and surface-enhanced Raman spectra of these analytes (see Figures2-5) are summarized in Table 2 (for the sulfides). Based on a consensus of the results presented here and shown inprevious studies, tentative assignments of the Raman and surface-enhanced Raman spectra of this related series of di-alkylmono-sulfide compounds are also summarized in Table 2. 3
  • Paper in preparation 4 2.600 0.750 2.400 0.700 A 0.650 A 2.200 0.600 2.000 0.550 1.800 1.600 B 0.500 0.450 1.400 0.400 1.200 C 0.350 B 1.000 0.300 0.800 D 0.250 0.200 0.600 0.150 0.400 0.100 C 0.200 E 0.050 0.000 0.000 -0.200 -0.050 350 500 750 1000 1250 1500 1750 1850 350 500 750 1000 1250 1500 1750 1850 Raman Shift, cm-1 Raman Shift, cm-1Figure 2. RS of A) HD, B) CEES, C) TDG, D) HEES and E) Figure 3. RS of A) 3ClEtSH, B) HOEtSH, and C) EtSH.EES. Conditions: neat liquids at 300 mW 5-minutes 785 nm. Conditions: neat liquids at 300 mW 5-minutes 785 nm. 5.500 2.200 5.000 A 2.000 A 4.500 1.800 4.000 B 1.600 3.500 1.400 3.000 1.200 C B 2.500 1.000 2.000 D 0.800 1.500 0.600 1.000 0.400 C 0.500 E 0.200 0.000 0.000 350 500 750 1000 1250 1500 1750 1850 350 500 750 1000 1250 1500 1750 1850 Raman Shift, cm-1 Raman Shift, cm-1Figure 4. SERS of A) HD, B) CEES, C) TDG, D) HEES and Figure 5. SERS of A) 3ClEtSH, B) HOEtSH, and C) EtSH.E) EES. Conditions: 1% v/v in MeOH at 100 mW 1-minute Conditions: 1% v/v in MeOH at 100 mW 1-minute 785 nm,785 nm, with silver-doped ODS/MTMS capillaries (HD with with silver-doped ODS/MTMS capillaries.silver-doped TMOS vials).The RS and SERS of these mono-sulfides and thiols exhibit several common features that appear to be characteristic forthis series of structurally related complexes. The spectra shown here are similar to those reported previously in theliterature. Specifically, the RS, SERS and subsequent spectral assignments of EES, CEES, and HD have been reported inseveral studies.25,3 The RS clearly demonstrate the rich vibrational information that allows for discrimination of these targetchemicals as a function of the structural perturbation imposed on the X-CCSCC-X skeletal backbone. In Figure 2A – 2E,the dominant spectral features for each of these sulfides is clearly evident in the 600-800 cm-1 region. In the case of EES(Fig. 2E), which is the simplest molecule of this aliphatic mono-sulfide series, and most importantly has been wellcharacterized by both IR and Raman spectroscopy in various states at different temperatures, including Ramandepolarization measurements combined with normal coordinate and ab initio calculations for assigning the vibrationalmodes,26,27,28,29 three dominant peaks between 600 – 700 cm-1 are discernible, and have been ascribed to C-S stretchingmodes. The association of features in this region with vibrational modes containing significant CS character is consistentwith the assignment of C-S stretching to peaks of moderate to strong intensity between 600 and 800 cm-1 in the spectrareported for various organic complexes of aliphatic monosulfides and thiols (see Figures 2 and 3).30,31,32,33,34,35,36Substitution of a terminal H in EES for an OH (see HEES and TDG in Fig. 2D-2C) or Cl (see CEES and HD in Fig. 2B-2A) results in noticeable changes, in particular some slight shifting of the three dominant peaks observed in the 600-700cm-1 region and the observation of additional peaks in the 700-800 cm-1 region that have gained intensity. Clearly, theselatter peaks involve contributions due to the OH and Cl substitution. Furthermore, the presence of two OH or Cl groups inTDG and HD respectively, results in an apparent splitting and enhancement of the peak relative to the correspondingfeature in the HEES and CEES spectra. The greater peak intensity observed for CEES and HD in this region is alsonoticeable. There are three additional regions of common interest in this series of sulfides between 800-1500 cm-1 (at 900-1100 cm-1, 1100-1400 cm-1, 1400-1500 cm-1) that are generally attributed to C-C stretching and CHn rocking, twisting,wagging, and or scissor modes. Modes in 300-400 cm-1 region are attributed to CHn deformation and CSC bending. Modes 4
  • Paper in preparation 5between 2800 cm-1 and 3100 cm-1 are generally associated with CHn stretching vibrations. The observed Raman spectralfeatures are summarized in Table 2. The spectral assignments of the sulfide series of compounds are based initially on theprevious studies of EES.26,27 Assignment of the peaks in the Raman of HEES, TDG, CEES and HD follow from theseinitial EES mode assignments and from direct comparison of the subsequent changes that occur following substitution ofthe terminal H with OH and Cl. The SERS of each of these sulfides (Figure 4) is clearly dominated by a common spectralfeature at ~629 cm-1 with additional peaks observed exhibiting little enhancement. In general, the SERS features appear tocorrespond to those peaks observed in the Raman spectrum, but due to interactions with the metal surface, these modesexhibit shifts in frequency and changes in relative intensity. The SERS spectra for the sulfides discussed below have beenassigned based on a comparison to the normal Raman spectrum, the SERS spectra of each sulfide, and theoreticalcalculations.The room temperature Raman spectrum of a neat liquid sample of EES shown in Figure 3 contains sixteen discerniblepeaks between 350 and 1650 cm-1, and is consistent with previously reported data. The most intense spectral peaks occur inthe 600-700 cm-1 region at 640, 656, and 693 cm-1, which have been attributed to C-S stretching modes.27 Theoreticalcalculations performed on the all-trans (TT) C2v structure for EES here and in previous studies28 predict only twovibrational modes with CS character in this spectral region, which can be described primarily as an in-phase CSC stretchand a lower frequency out-of-phase CSC stretching counterpart. Based on previous vibrational and theoretical studiesreported, the additional number of peaks which complicate this spectral region of EES has been attributed to theconformational properties associated with various dialkyl sulfides.26 Preferential assignment of the higher frequency C-Smodes at 689 cm-1 (see Reference 27, but not observed here) and 693 cm-1 to the TT isomer, or in fact any other modesexclusively to a specific conformer is still a matter of debate. Based on the results presented here in this study for the seriesof related sulfide complexes, an alternative assignment that we prefer is that the peak at 693 cm-1 may involve a CH3rocking mode contribution. The peak positions and assignments for EES are provided in Table 2. The SERS spectrum ofEES measured as a 1% (v/v) methanolic solution is shown in Figure 4, and taking into account the observed frequencyshifts upon interaction with the silver surface, the overall appearance is similar to the Raman spectrum of the neat liquid.However, there are noticeable differences in the general pattern within the 600 to 800 cm-1 region. In particular, only asingle peak at 629 cm-1 is distinctly observed between 600 and 700 cm-1, and as shown is significantly enhanced relative toall other peaks. Since it is anticipated that EES will interact with the electropositive silver surface exclusively through theS atom (via the sulfur electron lone-pairs) as reported,25 the very intense peak at 629 cm-1 is similarly ascribed to a C-Sstretching mode consistent with previous vibrational assignments in this region of the Raman spectrum.37 It is believed thatthis interaction shifts the C-S mode from 656 to 629 cm-1. A similar shift of 26 cm-1 has also been observed between theRaman and SERS spectra for CH3CH2SH (ethanethiol), and in other simple alkanethiols as well.38 It should be noted thatthe adsorption of thiols occurs through the S of the thiolate anion formed upon scission of the S-H bond, which is clearlyevident in the NR spectrum of the neat thiol as an intense peak at 2570 cm-1 but absent in the corresponding thiol SERS (seeFigure 5). This was supported by our measurement of the NR of the thiolate (deprotonated thiol in 1N KOH), whichconfirmed the absence of an S-H stretch consistent with previous NR and SERS studies of thiolates such as EtS-.38 Thissignificant shifting of C-S modes to lower wavenumbers in the SERS of thiolates and sulfides has been attributed to theelectron donor properties of sulfur and subsequent redistribution of electron density in the C-S bond upon adsorption of themolecule (via S) to the electropositive silver surface, and to a lesser extent to a relative increase in the effective mass of thesulfur atom as a result of this interaction.39,40 With the exception of the 1074 cm-1 Raman peak that has disappeared and theappearance of a peak in the SERS at 1139 cm-1 that has gained intensity, all other Raman features appear to exhibitcorresponding SERS features, albeit at shifted frequencies. Peaks of modest intensity at 967 and 1046 cm-1 are shiftedslightly relative to their Raman counterparts, and are assigned as a C-C stretch and CH3 rocking modes respectively. Theadditional peak associated with these modes in the Raman spectrum at 1074 cm-1 has lost intensity and shifted such that it isnot clearly observed in the SERS. A peak at 1139 cm-1 is weakly observed, that may correspond to an extremely weak1158 cm-1 Raman peak. The remaining SERS spectral peaks at 1205, 1239, 1246, 1263, 1282, 1369, 1428 and 1448 cm-1are also considerably less intense, and with the exception of the 1205 and 1282 cm-1 peak, appear to correspond tovibrational modes observed at similar frequencies in the Raman spectrum (see Table 2). In addition, peaks of weakintensity at 2863, 2917 and 2960 cm-1 are shifted relative to the corresponding modes assigned as CH stretches in theRaman spectrum. A peak between 300 - 400 cm-1 at 380 cm-1 is also observed, and associated with CSC bending. Theassignment of the Raman and SERS spectra of EES are summarized in Table 2.It is also worth pointing out that the SERS of EES is somewhat similar to that of EtSH (1.0% and 0.1% v/v in MeOH)measured under identical conditions (see Figure 5). The slight frequency shifts of corresponding features and uniquedifferences between 300 – 3000 cm-1 (such as the C-S stretch at 633 cm-1 and the absence of a CSC bend at 385 cm-1) in theSERS of EtSH indicate that the adsorbed species of the EES sample measured on silver is not ethane thiolate (EtS-), but isinstead more than likely intact sulfide (EES) as was reported.25 The SERS spectra of MMS (data not shown) is alsoreported to be that of the intact sulfide, which suggests photo-degradation via C-S scission does not occur spontaneously 5
  • Paper in preparation 6upon adsorption, and under the appropriate conditions does not degrade to MeSH upon irradiation.22 These previousstudies provide confidence in the stability of the aliphatic mono-sulfide on the metal surface following adsorption. Thesimplest mechanism to consider regarding the absence of photodegradation in these dialkyl sulfides can be attributed to thefact that their absorption bands are below 260 nm (e.g. HD), far from resonance with the 785 nm laser employed here.However, it must be considered that the absorption features of the analyte will change upon adsorption, and this change(broadening of band and energy shift) depends on the strength of the surface interaction, and thus the electronic nature ofthe analyte and metal substrate, and subsequent orientation.20 A final point to consider regarding the similar SERS spectrain the absence of degradation of EES to EtS- (and ethane) is the molecular orientation of the adsorbed parent sulfide. It isknown that modes which gain appreciable intensity relative to the other peaks suggest an orientation normal to the surface.Such modes are coupled to the plasmon field more effectively than for modes interacting with the surface in a parallelfashion.18 The relative frequency and intensity of the 629 cm-1 mode in the SERS spectrum implies that EES is orientedsuch that the sulfur atom is interacting with the silver surface and the CH2 group(s) directed away from the surface.Although, there appears to be no degradation of the sulfide to the thiolate, the similarity between the SERS of EES andEtSH may reflect that the sulfide orients on the surface such that one arm is parallel to the surface and the other arm is tiltedaway from the surface. The previous SERS study of EES and MMS suggested that the C2 conformation is preferentiallyadsorbed on the silver surface.25 Additional calculations are in progress to explore the affects of different conformationsand subsequent geometric and electronic structure relationships on the observed vibrational properties and SERS-responsewithin this series of sulfides.The next simplest chemical studied in this series of structurally related mono-sulfide compounds is HEES, which contains asingle hydroxyl group in contrast to TDG (and TDG-SO) discussed below with two such terminal groups. In addition,HEES is reported to be the primary hydrolysis product of CEES (a less toxic vesicant that also serves as a simulant of HD).The analysis of the Raman and SERS spectra of HEES follows from that previously described above for EES, and is alsosummarized in Table 2. The Raman spectrum of HEES presented in Figure 2 is very similar to that of EES. However,subtle spectral differences regarding relative peak positions and intensities as well as the appearance of new features areevident, which result from substitution of the heavier OH group for a terminal methyl H, and subsequent reduction in themolecular symmetry of EES (e.g. from idealized all-trans C2v to CS). Again the most intense peaks are observed in the 600-700 cm-1 region, specifically at ~640 (sh), 656 and 688 cm-1, that appear to be a characteristic feature of this dialkyl-monosulfide series. Calculations initiated here in this study on the all-trans structure predict two vibrational modes withsignificant CS character in this region, an C-S stretch of the SCCH3 moiety and a higher frequency C-S stretch involvingprimarily the HOCCS arm of the sulfide. Furthermore, the calculations suggest that this higher frequency C-S stretchingmode has some XC (OC) character mixed in. The 640 cm-1 feature and dominant 656 cm-1 peak are assigned to theserespective C-S stretching modes that could alternatively be described as skeletal stretching modes with SC and COcharacter, while the 688 cm-1 peak is tentatively assigned to a CH3 rock. The two peaks at 758 and 776 cm-1 could representthe CX + SC asymmetric counterparts of the previous modes with significant CO contribution (or alternatively assigned asCH2 wags). A comparison of relative peak intensities suggests that these two modes in HEES are enhanced with respect tothe corresponding peak(s) in EES. A distinct peak is also discernible in the 800 – 900 cm-1 region at 822 cm-1. The spectralregion of HEES between 900 and 1100 cm-1 is similar to that of EES, exhibiting common features at 975 and 1047 cm-1.Spectral differences between EES and HEES in this region are revealed by a weak peak resolved at 947 cm-1, the apparentshift of the 1074 cm-1 peak to 1064 cm-1 (sh), and a peak now appearing at 1010 cm-1 that has comparable intensity relativeto that at 1047 cm-1. C-C stretching modes are typically assigned to peaks in this region. The peaks in the 1171 to 1453cm-1 region are attributed to CH2 wags, twist and scissor modes respectively (see Table 2). The spectrum of HEES above2700 cm-1 is similar to EES, and exhibits a feature at 2732 cm-1, with intense peaks at 2874, 2926, and 2980 (sh) cm-1assigned to CH stretching. The SERS of HEES (Figure 4) appears to exhibit many of the same features observed in theRaman spectrum. However, only two distinct peaks are revealed in the 600 – 800 cm-1 region. A dominant 629 cm-1 peakis significantly enhanced relative to the weak 714 cm-1 peak in this region, and all other peaks as well. With the exceptionof the peaks at 1020 to 1050 cm-1 and at 1143 cm-1 that are slightly enhanced and correspond to the peaks at similarfrequencies in the Raman spectrum, all other SERS features have very weak intensity. The main difference here betweenthe SERS of EES and HEES is the disappearance of the 975 cm-1 peak in EES and subsequent enhancement of a 1020 cm-1peak in HEES relative to the common 1050 cm-1 peak. To evaluate the possibility of C-S cleavage in HEES (and TDG),the Raman and SERS of HOEtSH were measured in addition to EtSH (see Figures 3 and 5). The SERS of HOEtSH shownhere and previously reported,37 is noticeably different to that of HEES, and supports that this sulfide remains intact.The Raman spectrum of TDG has numerous peaks in the fingerprint region (Figure 2). The spectrum is very similar to theRaman of HEES. Calculations performed on the all-trans (TT) C2v structure for TDG here predict that many of the peaksbelow 900 cm-1 consist of skeletal or backbone modes and contain both SC and CO character. A peak with moderateintensity occurs at 402 cm-1 that is assigned to a skeletal bend consisting of a CSC scissor mode and the CCO bendingmodes. A peak with little intensity occurs at 479 cm-1 and could be the asymmetric counterpart of the previous mode.Overlapping peaks occur at 641, 658, and 687 cm-1, which are assigned to two skeletal stretching modes with both SC and 6
  • Paper in preparation 7CX character, and a CH2 rocking mode, respectively. Again as was observed for HEES, these modes are less resolved thanfor EES. The asymmetric version of these modes again form a doublet at 734 and 770 cm-1. Three peaks at 947, 1012, and1043 cm-1 are assigned to C-C stretches, while peaks at 1180, 1231, 1289, 1424, and 1467 cm-1 are assigned to various CH2wagging, twisting and scissor modes. The SERS of TDG contains many of the same peaks observed in the correspondingRaman spectrum. The most prominent difference is that there appear to be only two distinct peaks between 600 and 800cm-1. Since it is expected that TDG will interact most strongly with the silver surface via the sulfur electron pairs, theskeletal stretching modes with the most S character are assigned to these peaks. It is clear that the SERS of TDG andHEES are different. Most importantly is that the SERS of TDG and HOEtSH are very different, which suggests cleavageof the C-S bond to HOEtS- (and EtOH) has not occurred. The SERS of TDG measured over time as a function of powerbetween 25 – 200 mW show that the intensity ratio of the 629 and 715 feature remains relatively constant (0.60). This datacombined with that for HOEtSH provide additional support that the TDG molecule does not readily degrade on the silversurface via scission of the C-S bond. Based on the previous discussion and results, the peak at 629 cm-1 is assigned to askeletal stretching mode consisting predominantly of CS character with some CO character. According to somecalculations reported for related chloroethyl sulfide complexes this mode consists of 64% SC and 10-20% CX.28Consequently, we assign the intense mode at 658 cm-1 in the Raman spectrum to a stretching skeletal mode consistingpredominantly of CS character with some CO character. The second feature at 715 cm-1 is only weakly observed in theSERS of HEES. Although most publications assign the lower frequency Raman peaks to CX and higher frequency peaks(700 cm-1 region) to CS, all authors concede that the reverse assignments are possible. Regardless, due to the stronginteraction between sulfur and silver, it is consistent for modes with significant S character to be shifted much more thanthose modes with less or no S composition relative to their normal Raman counterparts. As a consequence, modes whichwere assigned to C-S stretching vibrations in the Raman spectrum are shifted to lower frequency in the SERS spectrum.Although oxidation of HD in water does not appear to be as dominant of a process as hydrolysis, it is known that HD canbe photo-oxidized to a chlorinated S=O analog bis(2-chloroethyl) sulfoxide. Furthermore, TDG can also be oxidized toTDG-SO following hydrolysis of HD. Thiodiglycol sulfoxide (TDG-SO), the primary oxidation product of TDG, waspurchased as a forensic sample at 1 mg/mL in methanol, which subsequently did not yield a good Raman spectrum.However, both TDG and TDG-SO at this concentration level are easily detected by SERS as shown in Figure 6. Althoughthe spectra are similar, there are several noticeable differences between the SERS of TDG and TDG-SO, which can beattributed to the electronic effects of the {S=O} moiety on the dialkyl mono-sulfide skeleton and interaction with the metalsurface. The TDG-SO spectrum is dominated by a peak at 608 cm-1 which we assign to the symmetric stretching skeletalmode consisting predominantly of SC character with some CO character. Two other peaks with reasonable intensity appearat 908 and 1031 cm-1. They are assigned to a symmetric S=O stretch and a C-C stretch, respectively. Although the latterpeak is coincident with a normal Raman peak for methanol, the other dominant peak characteristic of MeOH at 2830 cm-1 isnot present in the SERS of TDG-SO. The shift of the characteristic CSC stretching mode observed at ~630 cm-1 in theSERS of the dialkyl mono-sulfides to lower frequency as shown here (~608 cm-1) appears to represent a spectral signatureresulting from the oxidation of the sulfur atom. 0.950 0.900 0.850 0.800 A 0.750 0.700 0.650 0.600 0.550 Figure 6. SERS of A) TDG and B) TDG-SO Conditions: 0.1% 0.500 v/v in MeOH at 100 mW 1-minute 785 nm, with silver-doped 0.450 0.400 ODS/MTMS/TMOS capillaries. 0.350 0.300 B 0.250 0.200 0.150 0.100 0.050 350 500 750 1000 1250 1500 1750 1850 Raman Shift, cm-1Although we have reported the Raman and SERS spectra of CEES (ClCH2CH2SCH2CH2H) and HD(ClCH2CH2SCH2CH2Cl), these spectra are included in Figures 2 and 4 for completeness. The spectra of CEES presented inFigure 4 were obtained from silver-doped sol-gel coated capillaries, and are very similar to the previous vial measurements.In that paper we assigned the peaks between 600 and 800 cm-1 exclusively to C-S and C-Cl modes for both molecules andboth types of spectra. The assignments were based on the references previously cited (w/r to RS and calculations).41,17,28,29,Here we prefer the assignments, which suggests these modes should be considered skeletal modes with both SC and C-Cl 7
  • Paper in preparation 8contributions. Although it is tempting to assign the dominant 629 cm-1 peak in the SERS spectrum of CEES and HD to C-Cl stretching based on a strong chlorine to silver interaction, the fact that very similar peaks occur at ~629 cm-1 in the SERSspectra for EES, HEES and TDG, chemicals that don’t contain chlorine atoms, suggests otherwise. The SERS of HD andCEES, although generally similar, exhibit slight differences between corresponding peaks, which suggests that potentialdecomposition of HD to CESH (and CEt being SERS-inactive) and CEES to CESH (and EtSH being not evident), areadsorbed on surface as intact sulfides (not as thiolates). This stability may reflect the influence of chlorine on the C-S bondstrength enabling CEES and HD to withstand such photo-degradation via C-S cleavage at the conditions imposed here inthis study.A major contribution for developing correlations between the physical and hydrolysis properties of HD has resulted fromstudies of related chloroethyl sulfide (CES) complexes including CEMS, CEES and CEPS.42,43,44 Therefore, we have alsoincluded this series in our SERS studies. Clearly the nature of the substituent group on the CES moiety has a profoundeffect on the SERS and Raman spectra as shown in Figures 7 and 8. In all cases, discernible differences resulting from thestructural perturbation of the alkyl group is observed. It is worth noting that the SERS of CEPS was identical for both 785and 1064 nm excitation. Similar results were obtained on the gold substrates (data not shown). A key feature regardingthese sulfides is that the differences exhibited between CEMS and CEES should allow SERS to distinguish between (2-chloroethyl-2-chloromethyl)sulfide (a schedule I vesicant) and HD. 9.000 5.000 8.500 8.000 A 4.500 A 7.500 4.000 7.000 6.500 3.500 6.000 B B 5.500 3.000 5.000 2.500 4.500 4.000 2.000 3.500 C C 3.000 1.500 2.500 1.000 2.000 1.500 D 0.500 D 1.000 0.500 0.000 350 500 750 1000 1250 1500 1750 1850 350 500 750 1000 1250 1500 1750 1850 Raman Shift, cm-1 Raman Shift, cm-1 Figure 7. SERS of A) CEPS, B) HD, C) CEES, and D) CEMS. Figure 8. RS of A) CEPS, B) HD, C) CEES, and D) CEMS. Conditions: 0.1% v/v in MeOH at 100 mW 1-minute 785 nm, Conditions: 0.1% v/v in MeOH at 300 mW 5-minute 785 nm with silver-doped ODS/MTMS/TMOS capillaries (HD with silver-doped TMOS vials).The effects of solvent on the SERS of CEES and HD, and on the SERS of the expected primary hydrolysis products aredemonstrated below in Figures 9 and 10. The noticeable differences observed between the SERS of CEES and HD in pureMeOH relative to the SERS of each obtained in water (freshly prepared or allowed to age) or in a mixture of alcohol/wateris consistent with previous kinetic studies which showed that the hydrolysis of these CES compounds is greater in a watersolution with an alcohol co-solvent relative to pure water, and for the most part are stable in pure alcohol.42 Furthermore, itappears that the primary hydrolysis products expected to be formed from CEES and HD are much more stable than theparent sulfide complexes in water as evident by the identical spectra obtained for HEES and TDG in water or MeOH. It isclear that due to the different solubility properties, and hence dissolution rates of CEES and HD in water, the hydrolysisrate is affected by the nature of the solvent used to measure the SERS of these sulfides. Although CEES is stable in MeOHand somewhat in fresh water, it is eventually hydrolyzed in pure water at a greater rate than for the less polar and less watersoluble HD, with hydrolysis in water for both accelerated in the presence of a co-solvent such as MeOH or isopropanol.HD is stable in water to an extent as was shown in a previous ESERS study,45 and is similar to that of HD in MeOH asshown here in this study. The induced hydrolysis of CEES in water or HD in water/isoproponal is expected to producechanges in the SERS spectra, which is based on the anticipated loss of chlorine and substitution with OH. However, asshown for both CEES and HD, the hydrolysis products do not exactly match with that of HEES and TDG respectively. Theloss (or shift) of the 700 cm-1 peak in the hydrolyzed spectra of CEES and HD supports the assignment of this mode ascontaining a chlorine contribution. The SERS of HD in the isopropanol/ water mixture was also investigated on the gold-doped sol-gel coated vials.3 In this, the spectrum was similar to that of HD measured on the silver-doped coated vialsshown in Figure 10B, with some slight shifting of peak positions. However, it was observed that additional peaks grew inover time and as the power was increased, which indicated photo-degradation of the sample was occurring. 8
  • Paper in preparation 9 50.000 1.700 1.600 A 45.000 A 1.500 40.000 1.400 35.000 1.300 1.200 B 30.000 1.100 25.000 1.000 20.000 B 0.900 C 15.000 0.800 0.700 10.000 0.600 5.000 0.500 D C 0.000 0.400 -5.000 0.300 0.200 -10.000 350 500 750 1000 1250 1500 1750 1850 350 500 750 1000 1250 1500 1750 1850 Raman Shift, cm-1 Raman Shift, cm-1Figure 9. SERS of 1% v/v A) HEES in water, B) HEES in Figure 10. SERS of 0.1% v/v A) TDG in water, B) HD inMeOH, C) CEES in water, and D) CEES in MeOH isopropanol/water, C) HD in MeOH at 100 mW 1-minute 785Conditions: 0.1% v/v in MeOH at 100 mW 1-minute 785 nm, nm, with silver-doped TMOS vials.with silver-doped TMOS vials.Furthermore, the significant shift of the C-S peak in the hydrolyzed spectra of HD from 629 to 619 cm-1 is similar to theshift of the corresponding peak in TDG to 618 cm-1 in TDG-SO, which may imply that photo-oxidation of HD to bis(2-chloroethyl) sulfoxide46 or related hydrolyzed species may have occurred. The results support the fact that the inherent 629cm-1 peak in the sulfides is due to SC/CX skeletal stretching modes, with the additional peaks observed for CEES and HDat higher frequency (700-722 cm-1) being due to increased C-Cl contributions to these modes.Table 2. Tentative vibrational mode assignments for Raman and SERS peaks for HD, its hydrolysis products, andsimulants.EES HEES TDG CEES HDNR SERS NR SERS NR SERS NR SERS NR SERS334 340/363 348 325/360 w 343 C(CH) def383 380w 403 402 398 m 379 w CSC + CCX bend 415/423sh vw 412/419 478 479640 s 640sh 641sh 637sh 631656 vs 629 vs 656 629 vs 658 630 vs 653 s 629 vs 649 629 s SC + CX stretch 672 m693 ms 688 687 699 vs 668 m 699 673 w CH3/CH2 rock 734 699 m762 vw 741 w 758 715 m 734 715 s 753 s 722 s 757 CX + SC stretch779 vw 776 770 807 mw 822/840sh 822 mw 826/846sh (819 mw) 855 vw 853 (950 mw) 947 947 (931 mw) 930 vw 940975 m 967 m 975 977 w 973 CC stretch1018sh (1015sh) 1010 1012 1008 s 1016sh vvw 1020 s 1038 m 1019/1054 1039 1047 CC stretch1047 vm 1046 s 1047 1050 s 1043 1039sh vm 1054 m1074 m 1064sh 1062sh (1139 w) 1171 1143 mw 1171 1141/1195vw 1197 1205 mw 1226 broad 1231 (1209 mw) 1216 w CH2 twist/ CH2 wag1250 mw 1239 mw 1247 broad 1247 vw CH2 wag1273 mw 1263 mw 1287 1266 mw 1289 (1274 mw) 1270 w 1285 1272 1289 m 12931380 w 1377 w 1382 1378sh 1382 vw CH3 def 1408sh 1408 1428 m 1413 1426 CHn def/ CH2 scissor1430 vm 1428 m 1428 1424 (1409 mw) 1443 m 14421452 ms 1448 m 1453 1448 w 1467 (1463 mw) 1454sh 1447 4. CONCLUSIONSThe ability to measure and identify the various hydrolysis degradation products with our SERS-active silver-doped sol-gel coated capillaries has been demonstrated. Furthermore, we have shown that the vibrational spectra of the degradationproducts are distinguishable from that of the parent CWAs, and could be used as an indicator to identify a specific agentpresent. The Raman spectra of these chemicals were somewhat different relative to their SERS spectral counterparts,suggesting that the molecular structure was affected by the silver interaction with the adsorbed analyte as expected. Therelative intensity of these modes changed significantly in the SERS spectra even for the same derivative, suggesting thestrong and changing interaction of this group with the silver surface. In the case of mustard and corresponding derivatives,all spectra were dominated by a peak near 629 cm-1 attributed to a C-S mode, which interacted significantly with the silversurface. The additional peak at ~700 to 722 cm-1 in CEES and HD are now assigned to skeletal modes with significantchlorine contribution. Measurements to determine the detection limits and pH dependence of these hydrolysis products and 9
  • Paper in preparation 10CWAs using our SERS-active capillaries are in progress. Calculations are in progress for modeling the orientation of theanalyte on the SERS-response. 5. ACKNOWLEDGMENTSThe authors are grateful for the support of the U.S. Army (DAAD13-02-C-0015, Joint Service Agent Water Monitorprogram), and the National Science Foundation (DMI-0215819). The authors would also like to thank Dr. SteveChristesen, for helpful discussions, and Mr. Chetan Shende for sol-gel chemistry development. 6. REFERENCES1 Lee, Y., Farquharson, S., “Rapid chemical agent identification by SERS”, SPIE, 4378, 21-26 (2001).2 Farquharson, S., Maksymiuk, P., Ong, K., Christesen, S., “Chemical agent identification by surface-enhanced Raman spectroscopy”, SPIE, 4577, 166-173 (2001).3 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., Smith, W., Morrisey, K., Christesen, S., “Chemical agent detection by surface-enhanced Raman spectroscopy”, SPIE, 5269, 16-22 (2004).4 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., Smith, W., “pH dependence of methyl phosphonic acid, dipicolinic acid, and cyanide by surface-enhanced Raman spectroscopy”, SPIE, 5269, 117-125 (2004).5 Spencer, K.M., Sylvia, J., Clauson, S. and Janni, J., “Surface Enhanced Raman as a Water Monitor for Warfare Agents in Water”, SPIE, 4577, 158-165 (2001).6 Tessier, P., Christesen, S., Ong, K., Clemente, E., Lenhoff, A., Kaler, E., Velev, O., “On-line spectroscopic characterization of sodium cyanide with nanostructured Gold surface-enhanced Raman spectroscopy substrates”, App.Spectrosc., 56, 1524-1530 (2002).7 S., Christesen, S.D., Lochner, M.J., Ellzy, M., Spencer, K.M., Sylvia, J., Clauson, S., “Surface Enhanced Raman Detection and Identification of Chemical Agents in Water” 23rd Army Science Conference, Orlando, 2002.8 Yang, Y., Baker, J., Ward, J., “Decontamination of chemical warfare agents”, Chem. Rev., 92, 1729-1743 (1992).9 Creasy, W., Brickhouse, M., Morrissey, K., Stuff, J., Cheicante, R., Ruth, J., Mays, J., Williams, B., O’Connor, R., Durst, H., “Analysis of chemical weapons decontamination waste from old ton containers from Johnston atoll using multiple analytical methods”, Environ. Sci. Technol., 33, 2157-2162, (1999).10 http://ehpnet1.niehs.nih.gov/docs/1999/107p933-974munro/abstract.html11 http://www.cbwinfo.com/Chemical/CWList.shtml12 S. Farquharson, A. Gift, P. Maksymiuk, F. Inscore “Surface-enhanced Raman spectra of VX and its hydrolysis products”, Appl. Spectroscopy, 59, 654-660.13 F. Inscore, A. Gift, P. Maksymiuk, S. Farquharson, “Characterization of chemical warfare G-agent hydrolysis products by surface-enhanced Raman spectroscopy” SPIE, 5585, 46-52, 2004.14 Jeanmaire, D.L., and R.P. Van Duyne, J. Electroanalytical Chem., 84, 1-20 (1977).15 Farquharson, S. and P. Maksymiuk, “Simultaneous chemical separation and surface-enhancement Raman spectral detection using silver-doped sol-gels, Appl. Spectrosc., 57, 479-482 (2003).16 Farquharson, S., Gift, A., Maksymiuk, P., Inscore, F., “Rapid dipicolinic acid extraction from Bacillus spores detected by surface-enhanced Raman spectroscopy”, Appl. Spec. 58, 351-354 (2004).17 S. Christesen, MacIver, B., Procell, L. Sorrick, D., Carrabba, M., Bello, J., “Nonintrusive analysis of chemical agent identification sets using a portable fiber-optic Raman spectrometer”, Appl. Spec., 53, 850-855 (1999)18 Suh, J.S., Moskovits, M., “Surface-Enhanced Raman spectroscopy of amino acids and nucleotide bases adsorbed on silver”, J. Am. Chem.,108, 4711-4718, (1986).19 Moskovits, M. “Surface-enhanced Raman spectroscopy: a brief retrospective”, J. Ram. Spectrosc., 36, 485-496 (2005).20 S. Joo, S. Han, K. Kim, “Surface-enhanced Raman scattering of aromatic sulfides in aqueous gold sol”, Appl. Spec., 54, 378-383, (2000)21 Sandroff, C., Hershcbach, D. “Surface-enhanced Raman study of organic sulfides adsorbed on silver: facile cleavage of S-S and C-S bonds”, J. Phys. Chem., 86, 3277-3279, (1982).22 S. Lee, K. Kim, M. Kim, “Electrochemical reduction of organic sulfides investigated by Raman spectroscopy” J. Phys. Chem. 96, 9940-9943 (1992).23 T. Joo, Y. Yim, K. Kim, M. Kim, “Dissociation of some aromatic sulfides on a silver surface: a surface-enhanced Raman spectroscopic study”, J. Phys. Chem. 93, 1422-1425 (1989).24 H. He, C. Hussey, D. Mattern, “Unsymmetrical dialkyl sulfides for self assembled monolayer formation on gold: lack of preferential cleavage of allyl or benzyl substituents”, Chem. Mater. 10, 4148-4153 (1998).25 T. Joo, K. Kim, M. Kim “Surface-enhanced Raman study of organic sulfides adsorbed on silver”, J. Molec. Struct.,16, 191-200 (1987).26 Christesen, S. “Vibrational Spectra and Assignments of Diethyl Sulfide, 2-Chlorodiethyl Sulfide and 2,2’- 10
  • Paper in preparation 11 Dichlorodiethyl Sulfide”, J. Ram. Spec., 22, 459-465 (1991).27 Ohta, M., Ogawa, Y., Matsuura, H., Harada, I., Shimanouchi, T., “Vibration spectra and rotational isomerism of chain molecules.IV. diethyl sulfide, ethyl propyl sulfide, and butyl methyl sulfide”, Bull. Chem. Soc. Jpn., 50, 380, (1977).28 Sosa, C., R.J. Bartlett, K. KuBulat, and W.B. Person, “A theoretical study of harmonic vibrational frequencies and infrared intensities of XCH2CH2SCH2CH2X and XCH2CH2SH (= H, Cl)”, J. Phys. Chem., 93, 577-588 (1993).29 Donovan, W., Famini, G., “ Conformational analysis of sulfur mustard from molecular mechanics, semiempirical, and ab-initio methods”, J. Phys. Chem., 98, 3669-3674 (1994).30 C. Kwon, M. Kim, K. Kim, “Raman spectroscopic study of 2-methyl-1-propanethiol in silver sol”, J. Molec. Struct.,16, 201-210 (1987).31 M. Ohsaku, H. Murata, Y. Shiro, “Part XV C-S stretching vibrations of aliphatic sulfides”, J. Molec. Struct.,42, 31-36 (1977).32 S. Lee, K. Kim, M. Kim, W. Oh, Y. Lee, “Structure and vibrational properties of methanethiolate adsorbed on silver”, J. Molec. Struct.,296, 5-13 (1993).33 M. Schoenfisch, J. Pemberton “Effects of electrolyte and potential on in situ structure of alkanethiol self-assembled monolayers on silver”, Langmuir, 15, 509-517 (1999).34 T. Joo, K. Kim, M. Kim, “Surface-enhanced Raman scattering (SERS) of 1-propanethiol in silver sol”, J. Phys. Chem. 90, 5816-5819 (1986)35 S. Cho, E. Park, K. Kim, M. Kim, “Spectral correlation in the adsorption of aliphatic mercaptans on silver and gold surfaces: Raman spectroscopic and computational study” J. Molec. Struct.,479, 83-92 (1999).36 a). Kudelski, A., Hill, W., “ Raman study on the structure of cysteamine monolayers on silver”, Langmuir, 15, 3162- 3168 (1999). b). Michota, A., Kudelski, A., Bukowska, J., “ Chemisorption of cysteamine on silver studied by surface- enhanced Raman scattering”, Langmuir, 16, 10236-10242 (2000).37 A. Kudelski “Chemisorption of 2-mercaptoethanol on silver, copper, and gold: direct Raman evidence of acid-induced changes in adsorption/desorption equilibria”, Langmuir, 19, 3805-3813 (2003).38 C. Kwon, D. Boo, H. Hwang, M. Kim, “Temperature dependence and annealing effects in surface-enhanced Raman scattering on chemically prepared silver island films”, J. Phys. Chem. B., 103, 9610-9615 (1999).39 Tarabara, V., Nabiev, I., Feofanov, A., “Surface-Enhanced Raman Scattering (SERS) Study of Mercaptoethanol Monolayer Assemblies on Silver Citrate Hydrosol. Preparation and Characterization of Modified Hydrosol as a SERS- Active Substrate”Langmuir, 14, 1092-1098, (1998).40 Wehling, B., Hill, W., Klockow, D., “Crosslinking of organic acid and isocyanate to silver SERS substrates by mercaptoethanol”, Chem. Phys. Lett., 225, 67-71 (1994).41 Christesen, S.D., "Raman cross sections of chemical agents and simulants", Appl. Spec., 42, 318-321 (1988).42 Y. Yang, R. Ward, T. Luteran, “Hydrolysis of mustard derivatives in aqueous acetone-water and ethanol-water mixtures”, J. Org. Chem., 51, 2756-2759 (1986).43 G. Wagner, B. MacIver, “Degradation and fate of mustard in soil as determined by 13C MAS NMR”, Langmuir, 14, 6930-6934 (1998).44 G. Wagner, O. Kolper, E. Lucas, S. Decker, K. Klabunde, “Reactions of VX, GD, and HD with nanosize CaO: autocatalytic dehydrohalogenation of HD”, J. Phys. Chem. B., 104 5118-5123 (2000).45 S. Christesen, K. Spencer, S. Farquharson, F. Inscore, K. Gonser, J. Guicheteau, “Surface-enhanced detection of chemical agents in water” in press CRC 2005.46 R. Gall, M. Faraj, C. Hill, “Role of water in polyoxometalate-catalyzed oxidations in nonaqueous media. Scope, kinetics, and mechanism of oxidation of thioether mustard (HD) analogs by tert-butyl hydrperoxide catalyzed by H5PV2Mo10O40”, Inorg. Chem., 33, 5015-5021 (1994). 11
  • Appendix P EDGEWOOD DATATables of SERS data collected during tests of CN, HD, and VX in water collected at Aberdeen (9/10-12/2002).An example table is shown below with sections numbered and described to guide analysis. 1. Chemical Name gives the chemical agent being tested. 2. The Concentration column gives the concentration of the chemical agent (A1-A5 for 5 conc.). 3. The Slot Number column gives the slot on the instrument where the vial was placed. Only the A slots (5) were used. B slots were inverted, and the software positioning program did not account for vial caps, which would have offset vial measurements. B slots were not used. 4. The Spectrum Number column labels each of the five spectra that were acquired for each vial. Five positions (pts) were measured 1 mm apart along the length of the vials. A glitch in the software program dropped the data for the first position of the 1 mg/ml data for every run (note c3 in table). 5. The remaining columns give the Peak Heights for the spectra that were collected. Peak Areas Tables are also supplied. 6. Each of the Peak Height columns is labeled with the primary stock solution from which they were created. 7. Run numbers represent the 9 repeats in pairs of A and B (3 for each stock solution). HD included a B pair for run #5 that included ethanol (isopropyl alcohol?) in the water. 8. At the bottom of each concentration is the average of peak heights for the 5 spectra for that vial. These rows are labeled “avg of 5 pts”. Except 1mg/ml are 4 pts.At the bottom of each table a preliminary analysis is performed for each concentration. 9. The average, standard deviation, and % error ([(Std/AVG)*100]) of each 5 pt average for each concentration. 10. The average, standard deviation, and % error for each pt for each concentration.The Tables are arranged by Day (1-3) and according to when the samples were measured (CN, VX, HD). Due to alimited supply of vials (350) only 2 DI stock solution repeats were performed for CN and VX. All others used 3repeats.
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005 1. Chemical Name 5. Individual Peak Height 3. Slot Number 2. Concentration 4. Spectrum Number 6. Primary Stock Solution 7. Run # CN Run #1 Run#2 Run #3 Run #4 Run #5 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 A B A B A B A B A0 mg/mL A1 S-00 0.93 0.58 1.52 1.1 0.59 0.74 0.69 0.84 0.44 A1 S-01 1.03 0.69 0.75 0.83 0.39 0.32 0.33 0.99 0.87 A1 S-02 0.34 0.93 1.3 0.59 0.46 0.8 0.71 0.82 0.86 A1 S-03 0.89 0.55 0.52 0.77 1.01 0.63 0.63 0.78 0.73 A1 S-04 c2 1.02 1.06 0.55 1.1 0.31 0.75 0.74 0.4 avg of 5 pts 0.7975 0.754 1.03 0.768 0.71 0.56 0.622 0.834 0.660.001 mg/mA2 S-00 0.81 1.18 0.54 0.6 1 1.17 0.67 0.58 0.6 A2 S-01 0.72 0.91 0.82 0.67 0.84 1.09 0.64 0.76 0.55 A2 S-02 0.64 1 0.95 0.87 0.34 0.77 0.54 0.43 0.64 A2 S-03 0.91 0.89 0.66 0.97 0.71 1 0.51 0.38 A2 S-04 1.18 0.72 1.07 0.54 1.1 0.38 0.57 0.8 0.79 avg of 5 pts 0.8375 0.944 0.854 0.668 0.85 0.824 0.684 0.616 0.5920.01 mg/m A3 S-00 2.73 5.64 0.84 0.98 2.17 0.61 1.65 0.98 1.7 A3 S-01 2.87 4.87 1.02 1.08 1.46 0.74 0.98 1.36 1.61 A3 S-02 3.21 4.51 1.07 1.66 0.87 1.08 0.89 1.25 1.43 A3 S-03 3.62 5.12 1.19 2.32 0.83 0.72 0.99 0.62 2.12 A3 S-04 3.71 5.22 1.16 1.6 1.62 0.77 1.63 1.01 2.13 avg of 5 pts 3.228 5.072 1.056 1.528 1.39 0.784 1.228 1.044 1.7980.1 mg/mL A4 S-00 114.53 120.31 51.27 112.48 180.36 172.23 172.18 47.45 86.26 A4 S-01 101.78 140.26 39.46 117.72 176.32 128.61 158.48 29.06 74.66 A4 S-02 84.3 139.96 37.3 124.12 161.55 109.33 140.81 27.03 233.71 A4 S-03 68.94 152.93 30.33 129.22 c2 84.59 125.04 21.75 224.99 A4 S-04 54.21 156.63 28.96 145.97 133.06 59.08 103.88 26.77 200.42 avg of 5 pts 84.752 142.018 37.464 125.902 162.8225 110.768 140.078 30.412 164.0081.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 137.54 130.04 140.68 128.19 107.57 115.86 111.98 158.04 110.23 A5 S-02 135.19 126.92 144.02 129.09 115.12 112.36 112.43 157.16 88.75 A5 S-03 135.41 127.21 145.46 126.39 115.59 113.76 115.62 152.16 112.18 A5 S-04 134.62 126.48 117.63 126.51 112.14 108.94 116.55 150.84 110.77 avg of 5 pts 135.69 127.6625 136.9475 127.545 112.605 112.73 114.145 154.55 105.4825 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.748389 0.137028 18.3097 0.747273 0.26647 35.65902 A2 0.763278 0.124498 16.31094 0.761591 0.226407 29.72819 A3 1.903111 1.386366 72.84734 1.903111 1.367165 71.83842 A4 110.9138 50.14485 45.21064 109.7341 56.65853 51.63257 A5 125.2619 15.59696 12.45148 125.2619 15.86328 12.66409 8. 5 pt average for this run & concentration 10. Average of all spectra peak heights for that concentration. 9. Average of conc. for all runs 2
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 1. Day 1. Cyanide in deionized water. 0.0001 mg/ml was observed. Limits: 2010.58-2241.13 cm-1. CN Run #1 Run#2 Run #3 Vial PSS-1 PSS-2 PSS-1 PSS-2 PSS-1 PSS-2 A B A B A B0 mg/mL A1 S-00 0.93 1.28 1.38 1.11 0.6 0.89 A1 S-01 0.58 1.51 1.24 0.98 0.42 0.6 A1 S-02 1.5 0.56 1.18 0.9 0.39 0.71 A1 S-03 1.27 0.67 0.84 0.86 0.55 0.8 A1 S-04 0.79 c2 1.14 1.65 0.72 0.37 avg of 5 pts 1.014 1.005 1.156 1.1 0.536 0.6740.001 mg/mLA2 S-00 7.49 3.78 0.95 1.89 6.38 0.93 A2 S-01 c2 3.47 2.26 1.3 6.68 0.68 A2 S-02 9.29 2.98 0.48 1.59 7.77 0.47 A2 S-03 9.03 2.89 1.5 1.07 8.43 0.59 A2 S-04 8.52 3.19 2 0.82 8.26 0.94 avg of 5 pts 8.5825 3.262 1.438 1.334 7.504 0.7220.01 mg/mL A3 S-00 12.25 11.71 5.49 1.27 1 0.66 A3 S-01 11.72 15.72 5.49 1.22 1.07 1.1 A3 S-02 11.75 15.08 5.02 1.17 0.85 0.98 A3 S-03 c2 c2 5.59 0.45 1.74 0.68 A3 S-04 10.11 14.35 6.3 1.05 1.85 1.06 avg of 5 pts 11.4575 14.215 5.578 1.032 1.302 0.8960.1 mg/mL A4 S-00 17.7 2.34 93.84 8.21 251.08 5.4 A4 S-01 20.43 2.64 75.28 14.01 239.64 4.1 A4 S-02 15.32 1.88 69.14 6.61 238.3 5.89 A4 S-03 c2 1.7 59.72 4.05 229.21 5.02 A4 S-04 39.82 0.63 55.83 4.13 216.1 2.54 avg of 5 pts 23.3175 1.838 70.762 7.402 234.866 4.591.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 A5 S-01 72.65 100.49 150.99 119.12 68.52 111.66 A5 S-02 92.93 101.55 149.72 112.84 62.89 107.99 A5 S-03 92.03 102.87 147.12 109.34 62.17 104.13 A5 S-04 92.53 105.32 135.97 108.8 57.03 99.2 avg of 5 pts 87.535 102.5575 145.95 112.525 62.6525 105.745 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.914167 0.24977 27.32213 0.911034 0.355893 39.06468 A2 3.807083 3.406328 89.47343 3.642414 3.136168 86.10136 A3 5.74675 5.828668 101.4255 5.240357 5.27767 100.712 A4 57.12925 90.78517 158.9119 58.29517 85.96108 147.4583 A5 102.8275 27.60459 26.84553 102.8275 26.3002 25.57701 3
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 2. Day 1. VX in deionized water. Only 1 mg/ml was observed (unless spectra are averaged).Limits: 435 - 551 cm-1. VX Run #4 Run#5 Run #6 Vial PSS-1 PSS-2 PSS-1 PSS-2 PSS-1 PSS-2 A B A B A B0 mg/mL A1 S-00 2 3.18 3.22 2.12 1.51 2.2 A1 S-01 1.91 2.4 2.18 2.31 1.3 1.77 A1 S-02 1.04 1.4 1.97 1.76 0.9 1.85 A1 S-03 2.02 2.21 2.2 3.01 0.88 2.1 A1 S-04 2.59 2.82 1.75 2.26 1.3 2.81 avg of 5 pts 1.912 2.402 2.264 2.292 1.178 2.1460.001 mg/mLA2 S-00 2.14 1.29 4.21 1.54 3.04 2.97 A2 S-01 3.34 1.94 5.58 2.56 2.26 3.72 A2 S-02 2.89 1.49 4.83 2.44 1.51 3.86 A2 S-03 2.46 1.62 4.13 1.01 1.88 4.33 A2 S-04 2.85 2.16 2.96 2.45 1.96 3.34 avg of 5 pts 2.736 1.7 4.342 2 2.13 3.6440.01 mg/mL A3 S-00 1.9 0.98 1.83 1.6 2.13 2.83 A3 S-01 2.81 1.94 1.27 4.27 1.45 3.38 A3 S-02 1.41 2.08 1.26 1.83 1.74 3.22 A3 S-03 1.43 2.29 1.4 2.11 1.7 3.57 A3 S-04 1.74 2.13 2.52 2.25 1.92 2.39 avg of 5 pts 1.858 1.884 1.656 2.412 1.788 3.0780.1 mg/mL A4 S-00 3.32 2.54 1.99 3.56 3.1 1.71 A4 S-01 2.56 2.61 2.18 3.69 3.5 3.47 A4 S-02 0.7 2.18 1.71 2.06 2.24 2.06 A4 S-03 2.65 1.64 1.98 1.87 1.67 2.33 A4 S-04 2.77 1.23 2.63 2.98 2.15 2.27 avg of 5 pts 2.4 2.04 2.098 2.832 2.532 2.3681.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 A5 S-01 5.82 14.07 8.13 6.29 6.65 7.13 A5 S-02 10.16 12.98 8.99 6.88 6.6 6.91 A5 S-03 9.59 12.16 7.63 7.16 10.41 7.11 A5 S-04 9.79 9.58 6.53 6.07 8.68 6.98 avg of 5 pts 8.84 12.1975 7.82 6.6 8.085 7.0325 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 2.032333 0.450563 22.16974 2.032333 0.622058 30.60808 A2 2.758667 1.037578 37.61159 2.758667 1.118342 40.53921 A3 2.112667 0.538993 25.51243 2.112667 0.754654 35.72046 A4 2.378333 0.290881 12.23046 2.378333 0.713172 29.98621 A5 8.429167 2.007744 23.81901 8.429167 2.264196 26.86144 4
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 3. Day 1. HD in deionized water. 0.1 mg/ml was marginally observed. Limits:578 - 703 cm-1. 10th columnis alcohol solvent. HD Run #7 Run#8 Run #9 Run #10 Run #11 Vial PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 Blank A B A B A B A B A B0 mg/mL A1 S-00 0.96 0.6 0.98 0.15 1.19 0.46 0.22 1.02 0.45 0.82 A1 S-01 0.68 0.6 0.84 0.83 1.14 1.14 0.35 0.81 1.16 0.75 A1 S-02 1.1 0.47 0.71 0.34 0.73 0.74 0.56 1.09 0.54 1 A1 S-03 0.92 0.84 0.36 0.94 0.6 0.59 0.8 0.78 0.71 1.04 A1 S-04 0.83 0.54 0.51 0.75 0.91 0.77 0.86 1.26 0.43 1.21 avg of 5 pts 0.898 0.61 0.68 0.602 0.914 0.74 0.558 0.992 0.658 0.9640.001 mg/mLA2 S-00 1.03 0.8 0.53 0.85 0.38 0.3 0.9 0.46 0.44 0.42 A2 S-01 0.39 0.54 0.5 0.6 0.61 0.77 0.64 0.73 0.82 0.6 A2 S-02 0.58 0.66 0.41 0.43 0.91 0.82 0.68 0.6 0.93 0.73 A2 S-03 0.59 1.04 0.55 0.68 0.44 0.67 0.71 0.79 0.52 0.66 A2 S-04 0.6 0.86 0.81 0.7 0.23 0.6 0.83 0.39 0.87 0.91 avg of 5 pts 0.638 0.78 0.56 0.652 0.514 0.632 0.752 0.594 0.716 0.6640.01 mg/mL A3 S-00 1.15 0.69 0.68 1.04 0.42 0.69 0.75 0.97 0.32 0.14 A3 S-01 0.51 0.83 0.46 0.62 1.3 1.04 0.35 0.59 0.77 0.56 A3 S-02 0.96 1.02 1.38 0.6 0.73 0.98 1.22 0.95 0.9 0.49 A3 S-03 0.27 0.63 0.34 1.12 0.72 0.42 0.47 0.27 0.46 0.65 A3 S-04 0.71 0.82 0.66 0.98 0.91 1.61 0.64 1 0.64 0.82 avg of 5 pts 0.72 0.798 0.704 0.872 0.816 0.948 0.686 0.756 0.618 0.5320.1 mg/mL A4 S-00 1.36 1.55 0.95 1.03 0.91 1.39 0.76 1.35 1.63 0.61 A4 S-01 0.43 1.04 1.2 0.88 1.44 1.7 1.12 1.32 0.95 0.44 A4 S-02 0.85 1.28 0.65 0.53 0.95 1.67 0.59 0.9 1.14 0.88 A4 S-03 1.31 0.74 1.66 1.05 1.09 0.98 0.56 0.99 1.01 0.61 A4 S-04 0.56 1.11 0.96 1.07 1.82 1.56 0.81 0.46 0.64 0.53 avg of 5 pts 0.902 1.144 1.084 0.912 1.242 1.46 0.768 1.004 1.074 0.6141.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 5.12 5.57 4.15 4.84 5.15 5.82 12.46 7.12 6.65 1.77 A5 S-02 5.26 5.16 3.75 4.19 4.51 5.34 13.32 6.49 4.35 0.74 A5 S-03 5.97 5.74 4.62 4.49 4.67 5.74 11.79 5.28 4.35 0.57 A5 S-04 5.29 5.84 5.41 4.44 5.99 6.3 10.8 6.69 4.58 1.56 avg of 5 pts 5.41 5.5775 4.4825 4.49 5.08 5.8 12.0925 6.395 4.9825 1.16 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.739111 0.157373 21.29213 0.739111 0.270831 36.64274 A2 0.648667 0.087926 13.5549 0.648667 0.194113 29.92498 A3 0.768667 0.101356 13.18592 0.768667 0.307679 40.02762 A4 1.065556 0.204921 19.23141 1.065556 0.360433 33.82579 A5 6.034444 2.35306 38.99381 6.034444 2.332559 38.65408 5
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 4. Day 2. Cyanide in RO water. 0.001 mg/ml was observed. Limits: 2010.58-2241.13 cm-1. CN Run #1 Run#2 Run #3 Run #4 Run #5 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 A B A B A B A B A0 mg/mL A1 S-00 0.91 0.54 0.93 0.83 0.8 1.2 1.1 0.71 0.71 A1 S-01 0.73 1.18 0.81 1.14 1.08 0.41 0.74 0.99 0.54 A1 S-02 0.87 0.85 1 1.02 0.46 0.8 0.88 0.44 0.93 A1 S-03 0.95 0.83 0.51 0.62 0.35 0.64 1.58 0.49 0.84 A1 S-04 0.85 0.86 1.11 c2 0.71 0.62 0.75 0.63 0.7 avg of 5 pts 0.862 0.852 0.872 0.9025 0.68 0.734 1.01 0.652 0.7440.001 mg/mA2 S-00 0.81 0.77 0.66 0.54 0.56 0.66 0.62 1.01 1.27 A2 S-01 0.76 0.86 0.96 0.41 0.47 1.08 0.39 0.82 0.89 A2 S-02 1 1 c2 0.85 0.76 1.18 0.5 0.54 1.37 A2 S-03 1 0.75 c2 1.06 0.66 0.53 1.27 1.01 1.63 A2 S-04 0.28 1.26 1.02 0.67 0.88 0.56 0.34 1.06 0.65 avg of 5 pts 0.77 0.928 0.88 0.706 0.666 0.802 0.624 0.888 1.1620.01 mg/m A3 S-00 3.92 0.49 0.83 2.36 5.6 1.37 4.39 4.07 3.16 A3 S-01 4.14 0.96 1.24 2.33 5.2 1.59 5.07 3.79 2.71 A3 S-02 3.96 1.02 1.14 2.06 5.96 1.47 4.16 4.61 3.22 A3 S-03 4.38 1.19 1.31 1.92 6.59 2.36 4.15 3.86 3.27 A3 S-04 6.01 1.56 2.13 2.15 339.08 2.87 4.01 3.48 3.34 avg of 5 pts 4.482 1.044 1.33 2.164 72.486 1.932 4.356 3.962 3.140.1 mg/mL A4 S-00 86.77 19.14 41.16 3.42 63.27 51.27 40.6 48.62 26.37 A4 S-01 78.59 14.56 39.44 4.05 59.76 51.58 42.16 37.58 27.34 A4 S-02 74.7 9.95 38.36 5.5 51.46 48.92 40.62 31.25 28.14 A4 S-03 76.52 7.48 34.83 6.65 50.15 45.35 39.14 26.27 30.36 A4 S-04 75.39 5.59 32.26 7.21 48.21 43.93 33.76 19.72 34.02 avg of 5 pts 78.394 11.344 37.21 5.366 54.57 48.21 39.256 32.688 29.2461.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 136.7 135.49 135.61 126.22 142.12 132.35 147.81 138.83 152.35 A5 S-02 141.39 140.03 131.02 127.16 139.88 127.28 147.56 141.42 151.65 A5 S-03 143.59 139.26 131.58 130.17 140.79 130.27 148.14 137.87 150.95 A5 S-04 139.08 c2 113.61 128.33 139.5 127.08 145.11 141 151.58 avg of 5 pts 140.19 138.26 127.955 127.97 140.5725 129.245 147.155 139.78 151.6325 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.812056 0.116633 14.3627 0.81 0.245167 30.26756 A2 0.825111 0.163772 19.84842 0.822558 0.299532 36.4147 A3 10.544 23.26352 220.6328 10.544 50.11288 475.2739 A4 37.36489 22.04945 59.01115 37.36489 21.59331 57.79039 A5 138.0844 8.384492 6.072004 138.0794 8.781913 6.360044 6
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 5. Day 2. VX in RO water. Only 1 mg/ml was observed (unless spectra are averaged).Limits: 435 - 551 cm-1. VX Run #6 Run#7 Run #8 Run #9 Run #10 PSS-3 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 A A B A B A B A B0 mg/mL A1 S-00 0.67 1.94 2.02 2.78 3.1 2.63 2.55 3.12 2.71 A1 S-01 1.53 1.61 2.53 2.95 3.2 4.39 3.59 3.34 2.69 A1 S-02 1.51 2.68 3 3.33 2.83 2.82 3.98 3.63 2.51 A1 S-03 2.16 1.57 3 2.92 3.06 2.45 3.92 3.49 2.06 A1 S-04 1.59 2.84 2.02 3.05 2.06 2.47 3.96 2.75 1.75 avg of 5 pts 1.492 2.128 2.514 3.006 2.85 2.952 3.6 3.266 2.3440.001 mg/mA2 S-00 1.2 1.95 2.77 1.97 2.27 2.7 2.64 3.53 2.57 A2 S-01 1.47 2.67 2.23 2.37 3.69 2.22 3.11 2.44 2.96 A2 S-02 1.58 1.57 2.02 2.23 1.18 2.89 3.11 2.16 2.04 A2 S-03 3 3.29 2.08 2.07 2.45 1.85 3.78 2.19 1.89 A2 S-04 2.84 2.92 1.78 2.77 2.14 2.24 2.83 1.52 2.16 avg of 5 pts 2.018 2.48 2.176 2.282 2.346 2.38 3.094 2.368 2.3240.01 mg/m A3 S-00 2.13 2.02 2.58 0.54 1.97 2.03 4.75 1.99 1.72 A3 S-01 3.03 2.46 2.77 1.17 2.12 2.75 3.03 2.07 1.78 A3 S-02 2.68 1.88 2.12 1.86 1.33 1.16 3.38 1.61 1.64 A3 S-03 3.52 2.76 2.39 2.16 1.74 1.19 2.06 2.11 1.6 A3 S-04 2.23 2.43 1.25 1.47 1.29 1.03 1.52 2.19 2.89 avg of 5 pts 2.718 2.31 2.222 1.44 1.69 1.632 2.948 1.994 1.9260.1 mg/mL A4 S-00 3.08 3.9 2.2 1.73 No Spec 2.29 2.33 3.21 2.44 A4 S-01 2.56 3.84 3.03 2.12 No Spec 3.15 2.34 3.07 4.08 A4 S-02 1.85 3.71 3.29 1.75 No Spec 2.92 1.53 3.11 3.27 A4 S-03 1.92 4.23 2.86 2.2 No Spec 3.4 2.48 3.11 2.17 A4 S-04 2.76 3.94 3.09 1.94 No Spec 2.1 2.88 2.54 3.33 avg of 5 pts 2.434 3.924 2.894 1.948 2.772 2.312 3.008 3.0581.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 4.27 5.49 14.2 11.73 12.99 12.51 12.37 5.13 12.1 A5 S-02 4.99 5.82 15.98 13.82 13.87 11.12 11.38 5.46 13.06 A5 S-03 4.94 5.41 15.78 14.69 9.14 11.16 11.83 5.43 14.89 A5 S-04 5.19 5.62 14.86 14.56 11.88 11.15 11.43 7.67 17.64 avg of 5 pts 4.8475 5.585 15.205 13.7 11.97 11.485 11.7525 5.9225 14.4225 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 2.683556 0.637901 23.77074 2.683556 0.771101 28.73429 A2 2.385333 0.29712 12.4561 2.385333 0.61856 25.9318 A3 2.097778 0.503016 23.97853 2.097778 0.758955 36.17901 A4 2.79375 0.595281 21.30759 2.79375 0.705218 25.24268 A5 10.54333 4.023486 38.16142 10.54333 4.010486 38.03812 7
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 6. Day 2. HD in RO water. 0.1 mg/ml was marginally observed. Limits:578 - 703 cm-1. HD Run #11 Run#12 Run #13 Run #14 Run #15 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 Blank A B A B A B A B A B0 mg/mL A1 S-00 0.35 0.6 0.63 0.63 0.67 0.69 0.6 0.92 0.61 0.45 A1 S-01 0.84 0.58 0.61 1.04 0.56 0.5 0.71 0.72 0.73 0.57 A1 S-02 0.4 0.82 0.7 0.67 0.75 0.59 0.57 0.57 0.58 1.02 A1 S-03 0.74 0.62 0.58 0.33 0.52 0.51 0.45 0.69 0.15 0.59 A1 S-04 0.64 0.98 0.6 0.9 0.33 0.88 1.15 1.01 0.52 0.78 avg of 5 pts 0.594 0.72 0.624 0.714 0.566 0.634 0.696 0.782 0.518 0.6820.001 mg/mA2 S-00 0.55 0.67 0.54 0.52 0.43 1.07 0.88 0.47 0.81 0.79 A2 S-01 0.47 0.45 0.69 0.85 0.69 0.81 0.59 0.83 0.68 0.54 A2 S-02 1.03 0.41 0.99 0.38 0.56 0.99 0.49 0.59 0.82 0.41 A2 S-03 0.67 0.5 0.45 0.57 0.69 0.63 0.53 0.46 0.45 0.89 A2 S-04 0.28 0.29 0.35 0.67 0.7 0.67 0.44 0.7 0.84 0.52 avg of 5 pts 0.6 0.464 0.604 0.598 0.614 0.834 0.586 0.61 0.72 0.630.01 mg/m A3 S-00 0.79 0.78 0.48 0.34 0.89 0.57 0.74 0.75 0.47 0.88 A3 S-01 0.44 0.5 0.7 0.45 0.74 0.29 0.33 0.79 0.67 0.6 A3 S-02 0.35 0.55 0.32 0.31 0.34 0.82 0.44 0.38 0.23 0.69 A3 S-03 0.55 0.28 0.5 0.58 0.57 0.36 0.83 0.26 0.8 0.69 A3 S-04 0.76 0.89 0.68 0.27 0.8 0.92 0.64 0.95 0.74 0.95 avg of 5 pts 0.578 0.6 0.536 0.39 0.668 0.592 0.596 0.626 0.582 0.7620.1 mg/mL A4 S-00 1.2 0.54 1.34 1.11 1.35 1.45 1.09 1 0.83 0.57 A4 S-01 1.42 0.68 1.44 1.1 0.77 1.35 0.56 0.63 1.19 0.89 A4 S-02 1.24 0.71 1.26 1.33 1.02 0.85 1.13 0.43 1.19 0.47 A4 S-03 1.53 1.37 1.26 0.8 0.48 0.88 0.38 0.71 1.35 0.73 A4 S-04 1.52 0.89 1.45 1.51 1.46 0.89 0.82 0.58 0.95 0.6 avg of 5 pts 1.382 0.838 1.35 1.17 1.016 1.084 0.796 0.67 1.102 0.6521.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 6.29 7.72 5.57 5.21 5.78 5.2 5.73 5.57 4.73 0.53 A5 S-02 5.8 6.76 5.74 6.28 5.3 5.22 4.16 5.45 4.1 0.43 A5 S-03 4.2 7.15 5.35 6.78 5.48 5.83 3.91 5.43 5.18 0.66 A5 S-04 3.22 7.43 5.34 6.77 5.35 4.32 3.93 4.76 5.5 0.65 avg of 5 pts 4.8775 7.265 5.5 6.26 5.4775 5.1425 4.4325 5.3025 4.8775 0.5675 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.649778 0.084472 13.00007 0.649778 0.19704 30.32429 A2 0.625556 0.101419 16.2126 0.625556 0.19673 31.44878 A3 0.574222 0.077785 13.54608 0.574222 0.213738 37.22222 A4 1.045333 0.243234 23.2686 1.045333 0.336206 32.16257 A5 5.459444 0.848521 15.54227 5.459444 1.020207 18.68701 8
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 7. Day 3. Cyanide in tap water. 0.001 mg/ml was observed. Limits: 2010.58-2241.13 cm-1. CN Run #1 Run#2 Run #3 Run #4 Run #5 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 A B A B A B A B A0 mg/mL A1 S-00 0.93 0.58 1.52 1.1 0.59 0.74 0.69 0.84 0.44 A1 S-01 1.03 0.69 0.75 0.83 0.39 0.32 0.33 0.99 0.87 A1 S-02 0.34 0.93 1.3 0.59 0.46 0.8 0.71 0.82 0.86 A1 S-03 0.89 0.55 0.52 0.77 1.01 0.63 0.63 0.78 0.73 A1 S-04 c2 1.02 1.06 0.55 1.1 0.31 0.75 0.74 0.4 avg of 5 pts 0.7975 0.754 1.03 0.768 0.71 0.56 0.622 0.834 0.660.001 mg/mA2 S-00 0.81 1.18 0.54 0.6 1 1.17 0.67 0.58 0.6 A2 S-01 0.72 0.91 0.82 0.67 0.84 1.09 0.64 0.76 0.55 A2 S-02 0.64 1 0.95 0.87 0.34 0.77 0.54 0.43 0.64 A2 S-03 0.91 0.89 0.66 0.97 0.71 1 0.51 0.38 A2 S-04 1.18 0.72 1.07 0.54 1.1 0.38 0.57 0.8 0.79 avg of 5 pts 0.8375 0.944 0.854 0.668 0.85 0.824 0.684 0.616 0.5920.01 mg/m A3 S-00 2.73 5.64 0.84 0.98 2.17 0.61 1.65 0.98 1.7 A3 S-01 2.87 4.87 1.02 1.08 1.46 0.74 0.98 1.36 1.61 A3 S-02 3.21 4.51 1.07 1.66 0.87 1.08 0.89 1.25 1.43 A3 S-03 3.62 5.12 1.19 2.32 0.83 0.72 0.99 0.62 2.12 A3 S-04 3.71 5.22 1.16 1.6 1.62 0.77 1.63 1.01 2.13 avg of 5 pts 3.228 5.072 1.056 1.528 1.39 0.784 1.228 1.044 1.7980.1 mg/mL A4 S-00 114.53 120.31 51.27 112.48 180.36 172.23 172.18 47.45 86.26 A4 S-01 101.78 140.26 39.46 117.72 176.32 128.61 158.48 29.06 74.66 A4 S-02 84.3 139.96 37.3 124.12 161.55 109.33 140.81 27.03 233.71 A4 S-03 68.94 152.93 30.33 129.22 c2 84.59 125.04 21.75 224.99 A4 S-04 54.21 156.63 28.96 145.97 133.06 59.08 103.88 26.77 200.42 avg of 5 pts 84.752 142.018 37.464 125.902 162.8225 110.768 140.078 30.412 164.0081.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 137.54 130.04 140.68 128.19 107.57 115.86 111.98 158.04 110.23 A5 S-02 135.19 126.92 144.02 129.09 115.12 112.36 112.43 157.16 88.75 A5 S-03 135.41 127.21 145.46 126.39 115.59 113.76 115.62 152.16 112.18 A5 S-04 134.62 126.48 117.63 126.51 112.14 108.94 116.55 150.84 110.77 avg of 5 pts 135.69 127.6625 136.9475 127.545 112.605 112.73 114.145 154.55 105.4825 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.748389 0.137028 18.3097 0.747273 0.26647 35.65902 A2 0.763278 0.124498 16.31094 0.761591 0.226407 29.72819 A3 1.903111 1.386366 72.84734 1.903111 1.367165 71.83842 A4 110.9138 50.14485 45.21064 109.7341 56.65853 51.63257 A5 125.2619 15.59696 12.45148 125.2619 15.86328 12.66409 9
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 8. Day 3. VX in tap water. Only 1 mg/ml was observed (unless spectra are averaged).Limits: 435 - 551 cm-1. VX Run #6 Run#7 Run #8 Run #9 Run #10 PSS-3 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 A A B A B A B A B0 mg/mL A1 S-00 5.18 2.59 3.89 2.56 3.1 2.17 2.87 2.13 2.27 A1 S-01 3.99 2.91 2.62 2.98 2.72 3.44 1.95 2.67 2.8 A1 S-02 4.44 3.07 1.45 3.59 2.42 3.58 2.88 3.14 2.99 A1 S-03 2.49 1.79 2.15 2.44 3.17 2.56 2.49 2.5 3.1 A1 S-04 3.05 1.59 1.54 2.44 2.75 4.06 3.38 3.04 1.83 avg of 5 pts 3.83 2.39 2.33 2.802 2.832 3.162 2.714 2.696 2.5980.001 mg/mA2 S-00 2.67 2.7 2.72 1.77 3.33 2.57 1.8 2.51 3.13 A2 S-01 2.28 2.65 2.82 1.65 2.94 2.66 2.88 1.99 2.29 A2 S-02 1.52 2.08 3.28 3.48 3.36 2.63 2 1.73 3.08 A2 S-03 2.89 3.59 2.92 1.97 3.59 2 2 2.69 2.9 A2 S-04 2.6 3.32 2.42 2.67 3.63 2.87 2.35 2.24 3.62 avg of 5 pts 2.392 2.868 2.832 2.308 3.37 2.546 2.206 2.232 3.0040.01 mg/m A3 S-00 2.13 1.41 2.21 1.56 1.95 2.46 2.83 2.3 3.08 A3 S-01 3 2.44 2.51 2.17 1.85 2.85 0.8 3.36 1.89 A3 S-02 2.21 1.81 1.43 1.61 1.64 2.98 2.26 3.24 2.77 A3 S-03 2.34 2.82 2.62 2.2 2.26 1.65 2.63 2.14 1.87 A3 S-04 1.78 2.33 1.49 2.19 2.24 1.96 2.6 2.44 2.61 avg of 5 pts 2.292 2.162 2.052 1.946 1.988 2.38 2.224 2.696 2.4440.1 mg/mL A4 S-00 3.05 1.72 3.33 3.42 2.5 1.82 2.45 2.07 3.13 A4 S-01 2.21 2.73 3.19 2.15 2.84 3.49 3.24 1.5 3.96 A4 S-02 1.86 2.6 4.04 2.02 2.14 2.53 1.93 2.43 4.6 A4 S-03 2.51 2.39 2.81 2.85 3.51 3.11 3.31 2.99 5.79 A4 S-04 2.82 3.02 3.85 2.54 3.49 4.27 2.8 2.19 5.43 avg of 5 pts 2.49 2.492 3.444 2.596 2.896 3.044 2.746 2.236 4.5821.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 14.64 10.34 9.42 4.67 12.93 10.58 11.27 7.83 16.3 A5 S-02 14.85 9.9 12.1 6.1 9.65 6.97 13.58 8.12 16.14 A5 S-03 14.91 9.89 12.06 5.68 11.12 7.27 13.71 9.08 15.12 A5 S-04 10.41 7.77 12.54 5.53 7.46 6.89 10.97 8.75 13.97 avg of 5 pts 13.7025 9.475 11.53 5.495 10.29 7.9275 12.3825 8.445 15.3825 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 2.817111 0.452542 16.06404 2.817111 0.757369 26.88459 A2 2.639778 0.401501 15.20967 2.639778 0.578291 21.9068 A3 2.242667 0.24068 10.73188 2.242667 0.538539 24.01334 A4 2.947333 0.708629 24.04305 2.947333 0.908479 30.82375 A5 10.51444 3.075776 29.25286 10.51444 3.228544 30.70579 10
  • “sf” RTA P2001#05 DOD SBIR Phase II Contract Number DAAD13-02-C-0015 Final Report September 2005Table 9. Day 3. HD in tap water. 0.1 mg/ml was marginally observed. Limits:578 - 703 cm-1. HD Run #11 Run#12 Run #13 Run #14 Run #15 PSS-1 PSS-2 PSS-2 PSS-3 PSS-3 PSS-1 PSS-1 PSS-2 PSS-3 Blank A B A B A B A B A B0 mg/mL A1 S-00 0.56 0.62 0.57 0.67 0.73 0.63 0.64 c2 0.69 0.63 A1 S-01 0.5 0.86 0.49 0.71 0.49 0.6 1.46 1.15 0.38 0.6 A1 S-02 0.34 0.75 0.17 0.66 0.76 0.74 0.9 0.84 0.56 0.36 A1 S-03 0.58 0.39 0.26 0.42 0.85 0.42 0.47 0.53 0.32 0.57 A1 S-04 0.56 0.66 0.71 0.61 0.55 0.98 0.28 0.52 0.21 0.38 avg of 5 pts 0.508 0.656 0.44 0.614 0.676 0.674 0.75 0.76 0.432 0.5080.001 mg/mA2 S-00 0.41 1.14 0.75 0.89 0.7 0.79 0.53 0.83 0.9 0.55 A2 S-01 0.32 1.03 0.78 0.61 1.12 0.86 0.38 0.58 0.27 0.74 A2 S-02 0.18 0.97 0.53 0.65 1.01 0.52 0.3 1.06 0.79 c2 A2 S-03 0.41 0.57 0.9 0.59 0.54 0.37 0.5 0.83 0.6 1.06 A2 S-04 0.53 0.86 0.59 0.58 0.74 0.46 0.27 0.46 0.58 0.44 avg of 5 pts 0.37 0.914 0.71 0.664 0.822 0.6 0.396 0.752 0.628 0.69750.01 mg/m A3 S-00 0.62 0.85 0.21 1.34 0.69 0.21 0.72 0.28 1.01 0.6 A3 S-01 0.62 0.41 0.59 0.6 c2 0.85 c2 0.5 0.52 0.53 A3 S-02 0.65 0.43 0.47 0.51 0.49 0.58 0.46 0.41 0.57 0.71 A3 S-03 0.4 0.61 0.31 0.59 0.36 0.69 0.69 0.27 0.39 0.31 A3 S-04 0.49 0.82 0.43 0.4 0.79 0.68 0.82 0.76 0.69 0.82 avg of 5 pts 0.556 0.624 0.402 0.688 0.5825 0.602 0.6725 0.444 0.636 0.5940.1 mg/mL A4 S-00 1.14 2.79 0.66 0.96 1.22 2.21 0.38 1.63 1.05 0.47 A4 S-01 1.35 3.73 0.93 1.32 1.46 1.25 0.83 0.99 0.52 0.79 A4 S-02 0.93 5.08 0.77 1.17 1.58 1.36 0.7 1.01 0.12 0.95 A4 S-03 1.49 3.68 0.43 1.05 1.78 1.38 1.48 1.36 0.79 0.63 A4 S-04 0.47 2.91 0.54 1.12 3.85 1.64 0.77 0.46 0.94 0.65 avg of 5 pts 1.076 3.638 0.666 1.124 1.978 1.568 0.832 1.09 0.684 0.6981.0 mg/mL A5 S-00 c3 c3 c3 c3 c3 c3 c3 c3 c3 c3 A5 S-01 5.25 6.09 5.74 4.68 5.75 5.21 4.57 5.89 4.13 0.51 A5 S-02 4.5 6.75 5.3 4.84 4.49 5.36 5.83 4.97 4.27 0.48 A5 S-03 5.27 6.44 5.08 5.09 4.51 5.09 5.44 5.05 4 0.32 A5 S-04 5.59 8.07 5.94 6.69 3.79 5.65 5.28 5 5.09 0.3 avg of 5 pts 5.1525 6.8375 5.515 5.325 4.635 5.3275 5.28 5.2275 4.3725 0.4025 Avg of the Vial Averages Avg of all Vial Points AVG STDEV %ERR AVG STDEV %ERR A1 0.612222 0.124312 20.30503 0.608864 0.242182 39.77608 A2 0.650667 0.180061 27.67332 0.650667 0.244237 37.53646 A3 0.578556 0.097801 16.90428 0.576279 0.219827 38.14593 A4 1.406222 0.936876 66.6236 1.406222 1.027279 73.05237 A5 5.296944 0.683861 12.91047 5.296944 0.848501 16.01868 11