Epa Epd06084 Final Report

434
-1

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
434
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
2
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Epa Epd06084 Final Report

  1. 1. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Report Type: Phase II EPA SBIR Final ReportDate of the report: May 2010EPA Contract Number: EP-D-06-084Title: Multiplexed Chemical Sensor for Water SecurityPI: Dr. Stuart FarquharsonBusiness name: Real-Time Analyzers, Inc.EPA contact: James GentryProject period: May 1, 2006 to May 31, 2010Research category: SBIR, Topic I1. Drinking Water and Wastewater Security (2004)Purpose of the research:The overall goal of this proposed program (through Phase III) is to provide the EPA with achemical sensor that can be multiplexed into water distribution systems to provide early warningof poisoned water supplies.Brief description of the research carried out:The overall goal of the Phase II program was to fully develop the proposed analyzer and improvesensitivity to detect poisons at 10 µg/L (10 parts-per-billion, ppb) in 10 minutes. This wasaccomplished by optimizing the surface-enhanced Raman active sol-gel chemical selectivity,ruggedizing the capillaries, developing a universal sampling system with a stream-to-capillaryinterface and a capillary-to-fiber optic probe interface, and developing a comprehensive analysisthat included a searchable spectral library of 96 poison related chemicals capable of rapidlyidentifying these chemicals.Research findings:Twenty target chemicals, consisting of chemical agents, their hydrolysis products, simulants,pesticides and toxic industrial chemicals, were measured reproducibly at 10 µg/L (10 ppb) in 10minutes, with a statistical confidence of 95% or greater! A universal and automated samplingsystem that controlled flow, pressure and delivery of water samples to the surface-enhancedRaman active capillaries, was successfully designed and used to measure samples from NewYork City’s Kensico Reservoir. This included measurement of methyl phosphonic acid (75ppb), thiodiglycol (100 ppb), and cyanide (100 ppb), the primary hydrolysis products of thenerve agents, mustard gas, and cyanide salts, close to or exceeding the required detection limits(10, 100, and 6000 ppb, respectively).Potential applications:In addition to the proposed application of monitoring water supplies to ensure safe drinkingwater, the proposed analyzer could be used by first responders to assess safety of any watersupply. It could also be used to evaluate groundwater contaminated by cyanide (leachingoperations) or chromium (plating operations). This entire document is considered Proprietary Information, except for this Cover Page and the Executive Summary. 362 Industrial Park Road Providing Chemical Information When & Where You Need It Middletown, CT 06457 1
  2. 2. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 “Multiplexed Chemical Sensor for Water Security” EXECUTIVE SUMMARYThe overall goal of this proposed program (through Phase III) is to provide the EPA with a chemical sensor that canbe multiplexed into water distribution systems to provide early warning of poisoned water supplies. This will beaccomplished by developing surface-enhanced Raman (SER) sensors that can be integrated into water supplysystems and coupled to a central Raman analyzer via fiber optics.The overall goal of the Phase II program was to fully develop the proposed analyzer and improve sensitivity todetect poisons at 10 µg/L (10 parts-per-billion, ppb) in 10 min (~the 5 day/5L values in Table E.1). This includedoptimizing the SER-active sol-gel chemical selectivity, ruggedizing the capillaries, developing a universal samplingsystem with a stream-to-capillary interface and a capillary-to-fiber optic probe interface, and developing acomprehensive analysis that includes rapid chemical identification. These goals were largely met as summarizedby the following accomplishments:1) The sol-gel chemistry was successfully optimized to achieve the required sensitivity of at least 10 µg /L (ppb) forall of the 20 target chemicals within 10 minutes using a solid phase extraction cartridge that was included in thesampling system. The Lowest Measured Concentrations (LMC) for these chemicals are summarized in Table E.1.SER spectra are shown in Figure E.1 for methyl phosphonic acid, thiodiglycol, and cyanide, the primary hydrolysisproducts of the nerve agents, mustard gas, and cyanide salts.Table E.1. Lowest Measured Concentrations (LMC) for the 20 primary chemicals studied compared to theRequired Detection Limit (RDL, Military Drinking Water Guidelines, Short Term, 19991), along with the parentchemical agents, stimulants, pesticides, chlorinated by-products and their selected hydrolysis products. Chemical Agents & Hydrolysis RDL (5-day/5L LMC Simulants (Abbreviation) Products (µg/L (ppb) (µg/L (ppb)) Sarin (GB) isopropyl methylphosphonic acid (IMPA) 28 10 Soman (GD) pinacolyl methylphosphonic acid (PMPA) 12 10 Tabun (GA) ethyldimethyl-phosporamidate (EDMPA) 140 Cyclohexyl Sarin (GF) cyclo methylphosphonic acid (CMPA) 28 10 VX ethyl methylphosphonic acid (EMPA), 15 10 EA2192, methylphosphonic acid (MPA), 1 di-isopropylamino ethanethiol (DIASH) 10 EA2192 same as for VX 30 Mustard (HD) thiodiglycol (TDG), 1,4-dithiane 100 10 2-chloroethyl ethylsulfide 2-hydroxyethyl ethyl sulfide (HEES) 10 (CEES, half mustard) 10 2-chloroethyl methyl sulfide same as for CEES (CEMS, HD simulant) 10 cysteamine S-phosphate sodium salt (CSPS, VX simulant) 10 Hydrogen Cyanide (HCN) cyanide (CN) 6000 0.1 Pesticides chlorpyrifos (CP) trichloropyridinol (TCP) 40 10 fonofos (FON) O,O-dimethyl hydrogen thiophosphate, 30 10 potassium salt (DMHTP) 10 methyl parathion (MP) dimethylthiophosphoric acid DMTPA 300 10 disulfoton (DS) disulfoton sulfoxide (DS-SO) 140 10, 10 Chlorination By-products 3,5-dichlorobenzoic acid (DCBA) 1500 10 4,4-dichlorobiphenyl (DCBP) 1400 12) The two most active sol-gel chemistries were successfully developed to withstand flow rates of 5 mL/min andpressures of 30 psi. The sample system was successfully designed to reduce flow and pressure to at least thesevalues. 2
  3. 3. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 Methyl Phosphonic Acid 100 Probability of Detection, % 95% Confidence Line 80 60 Thiodiglycol 40 20 Cyanide 0 20 040 60 80 100 Probability of False Positive, % Figure E.1. Surface-enhanced Raman spectra of 10 Figure E.2. Receiver Operator Characteristic curves for µg/L (ppb) methyl phosphonic acid (MPA), 5 µg/L (ppb) methyl phosphonic acid using the raster thiodyglycol (TDG), and sodium cyanide (CN). program (green) and discrete points (red). The black line is the probability of a random guess (50/50).3) Receiver operator characteristic (ROC) curves were used to demonstrate that the required sensitivity could bereproducibly achieved 95% of the time with a 3 minute spectral acquisition for methyl phosphonic acid,thiodyglycol, cyanide, fonofos, dichlorobenzoic acid, and sunset yellow (a food dye selected for field studies).However, this required scanning the length of the capillary (rastering, Figure E.2), which was not implemented inthe final sampling system.4) Software was written that successfully identified any of 96 chemicals within a spectral library data base,consisting of chemical agents, pesticides, toxic industrial chemicals, and hydrolysis products. The spectral searchsoftware ranks all of the chemicals based on the closest match to the unknown. The analysis is virtuallyinstantaneous (<< 1 sec, Figure E.3)Figure E.3. Spectral search software showingidentification of unknown sample (10 ppb MPA Spectral Match (MPA)in water) as MPA using the 96 component library. Measured UnknownConditions: 80 mW, 785 nm, 1-min.Note the following ranking of phosphatecontaining chemicals (a score greater than 0.4represents a mismatch):Hit Quality Name0 0.174 MPA1 0.477 DEHDTP2 0.498 EMPA3 0.512 CMPA4 0.522 DMHP5 0.524 VX5) A computer controlled sample system was designed and successfully built that was capable of being connected tovirtually any water supply. It controls the water flow rate and pressure, directs the sample first through a solid phaseextraction cartridge (for 5 min) into a waste container, then switches flow to pass methanol through the cartridge andtransfer the concentrated sample to the SERS-active capillary (for 5 min). The flow is reset to introduce the nextsample, while the SER spectrum is acquired using a fiber optic coupled Raman spectrometer (Figure E.3). Analysisis updated every 10 minutes. 3
  4. 4. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 Sample In Waste Bypass SERS Capillary SPE A B MeOH Waste D CFigure E.4. A) Photograph of prototype Raman analyzer with fiber optic probe connected to B) the sampling system.The yellow line shows the sample flow through the SPE during the concentration step. The red line shows the flowof methanol through the SPE to the SERS Capillary during the extraction and delivery step. C) User Interfacesoftware used to control the sample and solvent flow. D) User interface of software used during operation (“More”shows spectral match as shown in Figure E.3).6) The automated sample system in conjunction with a Raman analyzer was successfully used to detect 75 µg/L(ppb) methyl phosphonic acid artificially added to water samples obtained from the Kensico Water Reservoir, whichsupplies New York City its drinking water (Figure E.5). The raster method was NOT used, which improvedsensitivity by more than a factor of 10 (and would therefore achieve the required sensitivity).Figure E.5. Surface-enhanced Raman spectrum of75 ppb MPA extracted from a Kensico Reservoirwater sample using the Figure E.4B sample system(SPE and SERS Capillary). The total analysistime is approximately 10 minutes. 4
  5. 5. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Limitations and Suggestions. Although 17 of 20 milestones were met, 3 were not. First, the proposed fiber-opticto SERS-capillary interface, which would use a Parker-Hannifin “Intraflow” machined block, was not pursued. Thiswas largely due to the fact that Parker-Hannifin delayed delivery by more than 1 year of the sample system Intraflowcomponents that they presumably already manufactured. Nevertheless, we successfully built a suitable (non-integrated) probe to perform the measurements. This probe could be readily modified to be a permanent componentof the sample system.Second, the proposed measurements of actual nerve agents at the US Army’s Edgewood Chemical and BiologicalResearch Center were never performed. Although the US Army provided a letter indicating that they would performsuch measurements, and we mailed SERS-active capillaries to them for these measurements, they were not able tofit these measurements into their schedule. We understand their priorities have changed to detecting biologicalwarfare agents.Third, the at-site measurements at Kensico Reservoir were never performed. This was due to the fact that theprototype system requires a number of modifications to perform these tests correctly. These modifications include:1) developing a motorized fiber optic probe system to “scan” the SERS capillary to achieve the necessary sensitivityand/or 2) incorporating additional solid phase extraction material into the SERS-active sol-gel to overcome sampledilution due to the sample system channels to achieve the necessary sensitivity, 3) mounting the probe to the samplesystem, 4) completing the top level software user interface so that it incorporates a) the flow control software, b) theRaman analyzer control software, c) the chemical identification software, d) the ROC curve concentration softwarewith alarms. It should be noted that the personnel at Kensico Reservoir were willing to perform the proposedmeasurements using the food dye sunset yellow, which we measured at 1 µg/mL (ppb).Fourth, although the proposed prototype was built using matching funds and tested using the CommercializationOption funds, due to the limitations cited above (primarily sensitivity), the proposed additional field tests were notperformed. Finally, for these same reasons, the Verification Option was not exercised.Finally, it is worth noting that we (Real-Time Analyzers) have continued talks with Hach and GE Power & Water(March, 2010, April 2010, respectively), and will pursue Phase III commercialization with these companies aspartners. 5
  6. 6. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 Confidential Proprietary Information TABLE OF CONTENTS Cover Page ................................................................................................................................................... 1 Executive Summary ..................................................................................................................................... 2 Table of Contents ......................................................................................................................................... 4 Program Description .................................................................................................................................. 41. Identification and Significance of the Problem or Opportunity................................................................... 62. The Phase II Program Schedule (verbatim from the Phase II proposal) ...................................................... 83. Detailed Summary of Phase II Work ........................................................................................................... 8 Task 1. Refine sol-gel selectivity and sensitivity ..................................................................................... 9 Task 2. Develop SER-active capillary durability .................................................................................. 20 Task 3. Develop Spectral Library.......................................................................................................... 30 Task 4. Test Sol-Gel Capillaries with Real Water Samples ................................................................... 59 Task 5. Establish Performance (ROC Curves) ...................................................................................... 63 Task 6. Design and Test Sample System .............................................................................................. 75 Task 7. Field Tests ................................................................................................................................ 874. Conclusions ............................................................................................................................................... 895. Publications ............................................................................................................................................... 896. Commercialization .................................................................................................................................... 90 References ................................................................................................................................................. 90 Appendix (Publications) ............................................................................................................................ 92 PROGRAM DESCRIPTION 1. Identification and Significance of the Problem or OpportunityThe nation’s drinking water supply is a potential target for terrorists. Chemical sensors or sensor systems are needed toprovide an early warning of poisoned water supplies to protect US citizens. This program will develop such a sensor tomeet this need. The remainder of this section is verbatim from the Phase I Proposal. The Phase II summary beginson page 8.1.a. The Problem or Opportunity - Countering terrorist attacks requires recognizing likely deployment scenariosand having the required technology to rapidly detect the deployment event. In addition to the expected use ofchemical agents released into the air, terrorists may also poison water supplies. The National Strategy for HomelandSecurity designates the Environmental Protection Agency with the task of securing the nations drinking water.2 Inresponse the EPA has defined four broad categories of both public and private labs based on analysis type:environmental, radiochemical, biotoxins, and chemical weapons.3 In the case of attack (real or suspected) the EPAhas developed protocols for collecting samples, sending them to EPA designated labs, and performing analyses. Inthe case of chemical warfare agents (CWAs) there are only two labs with the surety to perform these analyses.Furthermore, the analytical methods employed (e.g. gas chromatography coupled with mass spectrometry) requiresample extraction and calibration, and are time consuming. The positive determination that a water supply iscontaminated is likely to take as much as a day. This is entirely inadequate for the prevention of widespread illness,death, and terror. To overcome this limitation, the EPA has identified a number of field test kits, but unfortunately,they lack chemical selectivity and yield positive response to other chemicals. Clearly, a system of integrated sensorswith chemical specificity is needed to monitor the safety of drinking water in real-time.1.b. The Innovation - We at Real-Time Analyzers (RTA) believe that a series of chemical sensors, based onsurface-enhanced Raman (SER) spectroscopy, can be multiplexed into water distribution systems to provide earlywarning of poisoned water supplies. The proposed analyzer would employ sensors composed of 1 mm diameterwindows coated with chemically selective sol-gels that will extract and concentrate target chemical agents,pesticides or harmful industrial chemicals from flowing streams (Figure 1.1). The sol-gel sensor will also containmetal particles to generate SER spectra of these analytes allowing detection of 10 microg/L in 10 minutes. Thecoated sensor windows will be hermetically mounted to a stainless steel flange, such that it can handle highpressures (100 psi) and variable temperatures (5-40 C). Fiber optics will allow placement of sensors at critical nodesthroughout the distribution system at distances up to 100 m from a central Raman analyzer. A 10-position fiberoptic coupling wheel interfaced to the Raman analyzer will allow sequential analysis of the nodes. Multiplexingsoftware and supervisory control and data acquisition (SCADA) system software will provide the appropriate 6
  7. 7. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010warnings to EPA and/or water authority personnel.The proposed SERS-active, chemically-selective Fiber Opticsensors are based on several important advances Coupled Probedeveloped at RTA. First, we have developed andpatented a sol-gel process that incorporates silver Fibers toand/or gold nanoparticles into a stable porous silica Ramanmatrix.4,5 Second, no special reagents, conditions or Analyzersample treatments are required, and aqueous solutionsranging in pH from 2 to 11 can be used. Third, the sol-gel process is highly reproducible, and we guaranteeSER-activity at 20% RSD for our Simple SERS Water Pipe SER-ActiveSample Vials, now sold commercially for 2 years Window(Figure 1.2). Fourth, we have used these metal-dopedsol-gels to measure SER spectra of several hundredchemicals,6-11 with typical detection limits of 10 mg/Lusing 100 mW of 785 nm and 3-min acquisition time.Fifth, we have measured cyanide (CN), mustard (HD), Figure 1.1. Idealized concept of a SERS-based chemicalVX, as well as several CWA hydrolysis products, (e.g. agent detection node integrated into a water distributionpinacolyl methyl phosphonic acid), and numerous system.pesticides at 10 mg/L in 1 minute, with estimated limits of detection of 1 mg/L (Figure 1.3). Sixth, the choice ofmetal and alkoxide can be used to develop chemically selective sensors. We have successfully developed sol-gelsthat select for polar-positive, polar-negative, weakly polar-positive, and weakly polar-negative chemical species.12Seventh, we can coat a variety of surfaces to produce a wide range of sensor designs, including the glass discsproposed here. We have filled capillaries and micro-channels to detect flowing samples, as well as to performchemical separations.13 1008 cm-1 band intensity for BA A 45 40.0-45.0 40 35.0-40.0 35 30.0-35.0 30 25.0-30.0 25 B 20.0-25.0 20 15.0-20.0 15 10.0-15.0 10 5.0-10.0 5 6 0 0.0-5.0 C 330 9 300 270 240 210 12 180 150 Height 120 90 along 15 60 30 15o increments around vial 0 vial (mm)Figure 1.2. Reproducible SER-intensity response for Figure 1.3. SER spectra of A) cyanide, B)benzoic acid over entire surface of a Simple SERS pinacolyl methyl phosphonic acid and C) fonofos,Sample Vial. Average = 29.1± 4.26 (14.6%) for 240 all at 10g/L in water. Conditions: 100 mW of 785points (10 sec per point). nm, 1-min.Finally, it is worth noting that RTA has developed an extremely rugged, compact Raman instrument that employsinterferometry for absolute wavelength accuracy and an avalanche Si detector that improves sensitivity by ~100times.14 And we are currently developing a portable, battery powered version of the system for the Navy, which willweigh 21.5 pounds, occupy 0.5 cubic foot, require 23.5 W, and will be capable of wireless communication.15 7
  8. 8. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 2. The Phase II Program Schedule (verbatim from the Phase II proposal)Performance Schedule (24 Months) Quarters 0 1 2 3 4 5 6 7 8Task 1 - Refine sol-gel chemistry (6 mo) 1 2 3 .Task 2 - Develop capillary durability (4 mo) 4 5 .Task 3 - Develop spectral library (2 mo) 6 7.Task 4 - Identify real sample interferents (3mo) 8 9 10 .Task 5 - Define performance (ROC) (4 mo) 11 12 .Task 6 - Design and test sampling system (3 mo) 13-16.Task 7 - Perform field tests (2 mo) 17 18 19 20. Milestones 1. Prepare various Chem. 2 sol-gel capillaries 11. Measure 5 conc, 5 samples 2. Test extraction and SER-activity for 20 analytes 12. Plot ROC curves, calc. K 3. Determine baseline LODs 13. Finalize sample system design 4. Develop capillary coating process 14. Build SERS-capillary interface 5. Test flow and pressure integrity 15. Build FO interface 6. Measure chemicals, calc LODs 16. Test sample system 7. Test library search algorithms 17. Obtain Kensico samples 8. Measure artificially prepared interferents 18. Perform Edgewood measurements 9. Measure real sample interferents 19. Perform Kensico measurements 10. Design solution (filter) as needed 20. Summarize Data in a Final Report. All data will be summarized in terms of existing and estimated (Phase III product) capabilities in the Final Report. 3. Detailed Summary of Phase II WorkThe overall goal of Phase II will be to fully develop the proposed analyzer and improve sensitivity to allow detectionat 10 microg/L in 10 min (~the 5 day/5L values in Table 2). This will include ruggidizing the SER-active sol-gelcapillaries, developing a universal sampling system with a stream-to-capillary interface and a capillary-to-fiber opticprobe interface, and developing comprehensive analysis that includes rapid chemical identification. Capabilitieswill be developed using real-world samples and performing two field tests. The American Water Works will supplynumerous samples from the NJ drinking water distribution system. One field test will involve the analysis of a fooddye artificially added to a NYC water supply, while the other field test, performed at the US Army’s EdgewoodChem Bio Research Center, will involve the analysis of HD and VX added to a close-loop water test system. 8
  9. 9. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 Task 1. Refine sol-gel selectivity and sensitivity. The overall objective of this task is to finalize the sol-gel chemistry so that the target chemicals can be detected at the required concentrations (e.g.10 microg/L (10 ppb)). This will be accomplished by improving chemical extraction and taking advantage of improved SER-active sol-gels to detect 20 targeted chemicals. Twenty primary target chemicals listed in Table 1.1 (Bold) were tested in this Task (as well as in Task 3) with a refined subset of the SERS-active sol-gel chemical libraries summarized in Table 1.2. The SER activities and lowest measured concentrations for the 20 chemicals and the 6 sol-gel libraries are summarized in Table 1.3. Table 1.1. Chemical agents, stimulants, pesticides, chlorinated by-products and selected hydrolysis products with the Military Drinking Water Guidelines (Short Term, 1999).16 Bold indicates the 20 primary chemicals to be included in this study. Chemical Agents & 5-day/5L 5-day/15L Hydrolysis Hydrolysis Simulants (mg/L) (mg/L) Half-Life* Products Sarin (GB) 0.028 0.0093 21.3 hours IMPA Soman (GD) 0.012 0.004 2.3 hours PMPA Tabun (GA) 0.14 0.046 4.1 hours CN/EDMPA Cyclohexyl Sarin (GF) 0.028 0.0093 21.3 hours CMPA VXL 0.015 0.005 82.1 hours EMPA, EA2192, MPA, DIASH EA2192 0.03 0.01 9 years same as for VX Mustard (HD)L 0.1 0.05 2-30 hours TDG, 1,4-dithianeL CEES (1/2mustard) 2-4hrs HEES CEMS (HD simulant) 1-2 hrs same as for CEES CSPS (VX simulant) HCN 6 2 (0.2)** Stable CN Pesticides CP 0.04 0.014 (0.09)** 35-78 days TCPL FON 0.03 0.0009 2 days DMHTP (EEPA) MP 0.3 0.1 (0.002)** 11.2 days DMTPAL DS 0.014 0.005 (0.01)** 5-12 hrs DS-SO Chlorination By-products DCBA 1.5 0.5 (0.06)** DCBP 1.4 0.5 * pH 7 to 7.5 and 20 to 25 oC, ** EPA MCL, L = to be measured as part of the spectral library. CN = cyanide, IMPA = isopropyl methylphosphonic acid, PMPA = pinacolyl methylphosphonic acid, EDMPA = ethyldimethyl-phosporamidate, EMPA = ethyl methylphosphonic acid, CMPA = cyclo methylphosphonic acid, MPA = methylphosphonic acid, DIASH = di-isopropylamino ethanethiol, TDG = thiodiglycol, CEES = 2-chloroethyl ethylsulfide, HEES = 2-hydroxyethyl ethyl sulfide, CEMS = 2-chloroethyl methyl sulfide, CSPS = cysteamine S-phosphate sodium salt, TCP = trichloropyridinol, EEPA = O-ethyl ethylphosphonothioic acid, DMHTP = O,O-dimethyl hydrogen thiophosphate, potassium salt, DMTPA = dimethylthiophosphoric acid, DS = disulfoton, DS-SO = disulfoton sulfoxide, DCBA = 3,5- dichlorobenzoic acid, DCBP = 4,4-dichlorobiphenyl, CP = chlorpyrifos, FON = fonofos, and MP = methyl parathion. Italics mean not in SERS library; of these GA, GB, GD, EEPA and DMTPA have not yet been measured. We are in process of measuring G-agents at Aberdeen. Chemicals in parentheses mean could not be purchased. Table 1.2. Updated summary of chemically-selective, SERS-active, sol-gel libraries (capillaries) used in Task 1.Chemistry Selectivity/Analyte Metal Solution A/ Metal precursor A (µL) B (µL) Solution B/ Sol-gel precursor Type M Component ratio volume volume Si-Alkoxide ratio + additional componentsstandard P-C Ag 1N AgNO3/28%NH3OH/CH3OH/H2OL1 polar - negative silver 5:1:10:0 100 120 TMOS/MTMS (1:6)L2 non-polar - negative silver 5:5:10:0 100 100 MTMSL3 non-polar – negative silver 5:5:10:0 100 175 MTMS/ODS/TMOS (5:1:1) P-C Au 0.25N HAuCl4 /70% HNO3L4 polar - positive gold 4:1 100 100 TMOS OTC Ag 1N AgNO3 /0.026M NaBH4L6 polar-negative silver 3:1 120 120 APTES (95/5 in EtOH)modified P-C (polymer) Ag 1N AgNO3/28%NH3OH/CH3OH/H2OL1_PEG polar - negative silver 5:1:10:0 100 120 TMOS/MTMS (1:6) + 10 PDMSL2_PEG non-polar – negative silver 5:5:10:0 100 120 TMOS/MTMS (1:6) + 10 PEGL3_PDMS non-polar – negative silver 5:5:10:0 100 100 MTMS/ODS/TMOS (5:1:1) + 10 PDMS Note: Initial metal precursors/reagents prepared in water unless noted. Sol-gel chemistries in Italics are new chemistries developed during two NASA PII SBIRs. P-C designates filled packed-capillaries and OTC designates open tubular capillaries. Si-alkoxide precursors: TMOS (tetramethyl-orthosiloxane), MTMS (methyltrimethoxy-siloxane), ODS (octadecyl-trimethoxysilane) and APTES (3- aminopropyltrimethoxysilane). Polymer additives: PDMS (polydimethyl-siloxane) and PEG (polyethyleneglycol). 9
  10. 10. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Table 1.3. SERS-activity (+/-) and LMC (ppb) summary of the 20 target chemicals measured (on L1-L6). CN CSP MPA DIASH EMPA IMPA CMPA PMPA CEES CEMS TDG HEES S L1 + + + - + + + + + + peg + + + + + + + + + + + - L2 + + + + + + + peg + + + + - + - + + + - L3 + + + + + + + + + + + + pdms + + + + 2/1 + L4 + - - + - - - - + + - - L6 + + + + + + + + + + + + Static L2 1k L1 1k L3 1k L3100 L3 1k L3 10k L3100k L3 10k L3100k L1 10k -1kL3 L6 1k L6 10 L6 10 L6 10 L6 100k L61000k L61000k L6 100k L6 1k L6 1k L3pdms10k L4 1k L4 1k Flow L2 1 L2 1k L3 1k -10 L3 L3 1k -1kL2 -1k L2 -1k L3pdms L3 1k L3 500wk L11k L2 1k L32/1 L2 100 -500L1peg L2 100 500 L4 50 SPE L2 0.1 L6 10 L3 1k L3 10 L2 10 L1 10 L2 10 L1peg10 L6 10 L4 10 L1peg 10 AIEX L3 10 L2 10 L3 10 L3 10 L2 10 L2 10 L3 10 L6 10 L6 1 CP MP FON DS DSSO DMHTP DCBA 44DCBP L1 + + + + + peg + + + + L2 + + + + + peg + + L3 + + + + + + + pdms - 2/1 + L4 - - wk - - - - + L6 + + + + + + + + Static L3 1k L3 1k L2 1k L3 1k -1k L3 L6 L6 50 L6 10 L6 10 100 L32/1500 L4 10 Flow L3 1k L3 1k -10 L3 L2 1k -1k L2 L2 1k L2 100 -1k L2 -1k L2 -1k L2 L1peg 1k L32/150 -1kL1peg -1k L1peg L4 0.1 SPE L3 10 L3 10 L3 10 L3 10 L3 10 L2 10 L1peg10 L6 10 L6 10 AIEX L2 10 L2 10 L3 10Red indicates successful low ppb measurements.SERS measurements were performed in glass capillaries (1.1 mm outer diameter, 0.8 mm inner diameter) filled withmetal-doped sol-gels. The basic design and use of the SER-active capillaries is shown in Figure 1.1, and areprepared as follows. The alkoxide and amine precursors are prepared according to Table 1.2, mixed, and then drawninto the capillary by syringe. Typically 0.1 mL of solution coats a 4 cm length of capillary. The sol solution gels in5 minutes, and a more rigid structure is obtained after 24 hours. A solution of 0.1g/100mL NaBH4 is drawn throughthe capillary to reduce the metal. This is followed by a 0.035% HNO3 acid wash, and then the capillary is ready tobe used. 10
  11. 11. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Fig.1.1. Photograph of silver-doped sol-gel coated melting point capillaries attached to syringes, before (top) and after (bottom)reduction with sodium borohydride. Note: capillaries filled with gold-doped sol-gels are similarly prepared, but reduced twice.Initial screening of the sol-gel SER-activity employed 1 mg samples in 1 mL HPLC grade methanol or water. For“static” measurements, 50 µL of the samples were drawn into the capillaries, which were mounted on an XY samplestage above a fiber optic probe coupled to RTA’s Industrial Raman Analyzer. Spectra were obtained using 80 to100 mW of 785 nm excitation at the sample and 1 minute acquisition time unless noted otherwise. Once the initialscreening was performed, the stock samples were serially diluted to determine sensitivity. Also, normal Raman(NR) spectra of the analytes were acquired as pure solids, neat liquids or solutions (in appropriate solvents) in glasscapillaries (or vials) using 300 mW at 785 nm for 5 minutes. Table 1.3 above shows the activity table for the 20primary chemicals screened on the different chemistries, as well as the lowest measured concentrations (LMC) usingthe static, flow and solid phase extraction methods. Figures 1.2 to 1.21show a stack plot of the NR (solid), NR(solution) and SERS respectively for the 20 target chemicals. Most of the SERS are for 100 or 1000 ppm (0.1 or 1mg/mL) and are intended to clearly show the Raman peaks (high signal-to-noise ratios) and are not intended to showthe lowest possible concentrations (which come later). A A B B C CFig.1.2. A) NR (solid), B) NR solution (20 mg/mL in Fig.1.3. A) NR (solid), B) NR solution (30 mg/mL inHPLC water) and C) SERS of 100 ppm sodium cyanide HPLC water) and C) SERS of 1000 ppm cysteamine S-in water on chem. L2_PEG. Conditions: A) and B) phosphate sodium salt in water on chem. L2.200mw, 785 nm, 5-min, and C) 80mW, 785 nm, 1-min. Conditions: as in Fig.1.2. A A B B C CFig.1.4. A) NR (solid), B) NR solution (400 mg/mL in Fig.1.5. A) NR (solid), B) NR solution (1000 mg/mL inHPLC water) and C) SERS of 1 ppm HPLC water) and C) SERS of 1000 ppmmethylphosphonic acid in water on chem. L6. di-isopropylamino ethanethiol in methanol on chem.Conditions: as in Fig.1.2. L2_PEG. Conditions: as in Fig.1.2. 11
  12. 12. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B B C CFig.1.6. A) NR (solid), B) NR solution (200 mg/mL in Fig.1.7. A) NR (solid), B) NR solution (250 mg/mL in3:1 HPLC water/MeOH) and C) SERS of 1000 ppm HPLC water) and C) SERS of 1000 ppm isopropylethyl methylphosphonic acid in methanol on chem. methylphosphonic acid in methanol on chem. L2.L3. Conditions: as in Fig.1.2. Conditions: as in Fig.1.2. A A B B C CFig.1.8. A) NR (solid), B) NR solution (saturated in 1N Fig.1.9. A) NR (solid), B) NR solution (200 mg/mL inKOH) and C) SERS of 1000 ppm 3:1 HPLC water/MeOH) and C) SERS of 1000 ppmcyclo methylphosphonic acid in methanol on chem. pinacolyl methylphosphonic acid in methanol onL2. Conditions: as in Fig.1.2. chem. L2. Conditions: as in Fig.1.2. A A B BFig.1.10. A) NR (neat liquid) and B) SERS of 1000 ppm Fig.1.11. A) NR (neat liquid), and B) SERS of 1000 ppm2-chloroethyl ethylsulfide in methanol on chem. L3. 2-chloroethyl methyl sulfide in methanol on chem.Conditions: as in Fig.1.2. L3_PDMS. Conditions: as in Fig.1.2. 12
  13. 13. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B BFig.1.12. A) NR (neat liquid), and B) SERS of 1000 ppm Fig.1.13. A) NR (neat liquid), and B) SERS of 1000 ppmthiodiglycol in methanol on chem. L3. Conditions: as in 2-hydroxyethyl ethyl sulfide in water on chem. L3.Fig.1.2. Conditions: as in Fig.1.2. A A B B C CFig.1.14. A) NR (solid), B) NR solution (100 mg/mL in Fig.1.15. A) NR (solid), B) NR solution (neat liquid)methanol) and C) SERS of 1000 ppm chlorpyrifos in and C) SERS of 500 ppm methyl parathion inmethanol on chem. L2. Conditions: as in Fig.1.2. methanol on chem. L2_PEG. Conditions: as in Fig.1.2. A A B BFig.1.16. A) NR (neat liquid) and B) SERS of 1000 ppm Fig.1.17. A) NR (neat liquid) and B) SERS of 1000 ppmfonofos in methanol on chem. L3. Conditions: as in disulfoton in methanol on chem. L1. Conditions: as inFig.1.2. Fig.1.2. 13
  14. 14. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A BFig.1.18. A) NR (neat liquid) and B) SERS of 1000 ppm Fig.1.19. SERS of 1000 ppm dimethyl hydrogendisulfoton sulfoxide in methanol on chem. L6. Conditions: thiophosphate in methanol on chem. L3. Conditions:as in Fig.1.2. as in Fig.1.2. Note; no pure sample was available to generate NR. A A B BFig.1.20. A) NR (solid) and B) SERS of 1000 ppm Fig.1.21. A) NR (solid) and B) SERS of 1000 ppm3,5-dichlorobenzoic acid in methanol on chem. L3. 4,4-dichlorobiphenyl in methanol on chem. L3.Conditions: as in Fig.1.2. Conditions: as in Fig.1.2.From the above it was found that chem. L2, L3 and L6 are universal chemistries for routine screening of the 20target chemicals at nominal concentrations. Once the screening was performed, the chemicals were serially dilutedto 10 ppb (desired sensitivity). Initially, two methods were experimented with to achieve the desired sensitivity.The first method was the static method, which simply involved loading a small sample plug over the sol-gel andmaking SERS measurement. The second method was the flow method, which involved flowing a fixed volume ofthe sample through the sol-gel capillaries.The static method, in general, allowed measuring a few chemicals in the range of 100 ppm to 10 ppb (for e.g. MPA,DS and DSSO at 10 ppb on chem. L6, CN at 100 ppb on chem. L2 and CEES at 1 ppm on chem. L4) as can be seenfrom Figures 1.22 (A) to 1.41 (A). Unfortunately, the static method could not achieve the desired sensitivity of 10ppb for all the 20 target chemicals. Thus flow experiments were performed to test the ability of the sol-gels toextract the target analytes by measuring the SERS signal as the sample flowed through a capillary as a function oftime.For the flow experiments, a syringe pump (Sage model 341B, Thermo Electron, Waltham, MA) was used to flowthe sample (10-50 mL) through the capillary at a rate of 1 mL/min until a signal was observed. SER spectralcollection was initiated when the sample solution entered the capillary and spectra were collected continuously (20sec/spectrum) for ~5-30 minutes. This was followed by stop-flow measurements (i.e. measure 9 points along thecapillary after flowing the fixed volume of sample). The flow method, in general, allowed measurements in therange of 1ppm to 10 ppb for few of the target chemicals, (for e.g. CN on chem. L2, DIASH on chem.L3, and DCBPon chem. L4 at 10 ppb, CEES on chem. L4 at 50 ppb and EMPA on chem. L3 at 1 ppm). See Figures 1.22 (B) to1.41 (B). Unfortunately, the flow method also did not achieve the desired sensitivity of 10 ppb for all the 20 targetanalytes. 14
  15. 15. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010In an effort to improve sensitivity several variations to the 3 chemistries (L3, L6 and L4) were performed bychanging the ratios of the metal to the alkoxide and by the addition of polymers like polydimethyl siloxane (PDMS)and polyethylene glycol (PEG). Table 1.4 shows the initial modifications made on chem. L3. NOTE: not allpermutations were tried.Table 1.4. Initial modifications for making chem.L3 more polar. Chem Selectivity/Analyte Metal Solution A/ Metal precursor A(µL) B (µL) Solution B/ Sol-gel precursor Type M Component ratio volume volume Si-Alkoxide ratio P-C Ag 1N AgNO3/28%NH3OH/MeOH MTMS/ODS/TMOS 5:5:10 5:1:1 L3 non-polar - negative Silver A = 25 + 25 + 50 100 175 B = 125 + 25 + 25 5:1:1 L31 less non-polar – neg. Silver A= 25 + 25 + 50 100 175 B= 125 + 20 + 30 100 175 B= 125 + 15 + 35 100 175 B= 125 + 10 + 40 100 175 B= 125 + 5+ 45 more polar – neg. 100 175 B= 125 + 0+ 50 5:0:2 L32 less non-polar – neg. Silver A= 25 + 25 + 50 100 170 B= 125 + 20 + 25 100 165 B= 125 + 15 + 25 100 160 B= 125 + 10 + 25 100 155 B= 125 + 5+ 25 more polar – neg. 100 150 B= 125 + 0+ 25 5:0:1Two alkyl phosphonic acids (APA’s), PMPA and EMPA were chosen for preliminary screening with the modifiedchem.L3. The preliminary results obtained for PMPA indicate that it is enhanced on the standard non-polarchem.L3 as opposed to the more polar L.3 chemistries (L.3_PDMS>L3>L32&L31). In contrast, the SERS-responseof EMPA appeared to be improved with these new modified chem. L3 polar subsets (L32>L31>L3). Note:L3_PDMS = inclusion of 10 microL of PDMS within chemistry L3. (chem.L3_PDMS) provided a static detectionof PMPA in water at 10 ppm, as opposed to 100 ppm for chem.L3.Similarly, 3 modifications were performed on chem.L6. In the first modification, 0.5% APTMS solution was usedin place of a 1% APTMS. This produced a better signal at 1 ppm, but the thinner coat resulted in lessreproducibility. In the second modification, a 10/1 ratio of 1% APTMS and 1% MTMS was used to make a morehydrophobic coating. In this case also MPA was only detected at 1 ppm. In the third modification, 1% aminopropyl 3-ethoxysilane (APTES) was used instead of APTMS. This resulted in a more uniform coat and betterreproducibility and MPA was reproducibly detected at 1 ppm to 125 ppb, and sporadically at 100 ppb.Finally, modifications to chem.L4 were made. This included making the chemistry more non-polar with theaddition of MTMS (6/1 TMOS/MTMS, chem3b), 1/1 TMOS/MTMS (chem3c) and PTMS (1/1 TMOS/PTMSchem4b_PTMS). CEES, CEMS and 44DCBP were measured on the modified chemistries. The SERS-response ismuch weaker on chem3c and chem4b_PTMS with respect to chemL4. Static chemL4 LMC = 10 ppb for 44DCBPwhile flowing 10 mL aqueous sample improved the LMC to 100 ppt. These modifications also however did notallow detection at the required sensitivity for all the 20 target chemicals using the flow method. However, it isworth pointing out that the standard and modified L1-L6 libraries were used to further test and extensively screenover 71 additional chemicals in Task 3, spanning a wide range of different classes and subclasses of relevance.As an alternative method to flow we investigated the use of solid phase extraction (SPE) and ion-exchange (IEX)techniques as a way to pre-concentrate the sample to achieve the desired sensitivity. SPE is a form ofchromatography designed to extract, partition, and/or adsorb one or more components (sample) from a liquid phase(sample matrix) onto stationary phase (sorbent). The steps involve 1) conditioning the SPE sorbent with methanoland water, 2) flowing the sample through the sorbent and 3) eluting the extracted sample with a solvent. As part ofthe method development, we experimented with various SPE sorbents (C2, C8 and C18), IEX sorbents (anionexchange and cation exchange), different flow rates, and eluting solvents (methanol, acetonitrile, dichloromethaneand hexane). These experimental conditions allowed us to develop SPE/IEX methods for all the 20 target analytes.Table 1.5 lists the different SPE/IEX conditions for all the target chemicals, while Figures 1.22 (C) to 1.42 (C)shows the SERS of the 20 chemicals at10 ppb obtained using the SPE/IEX pre-concentration method. 15
  16. 16. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Table 1.5. SPE/IEX sample pre-concentration conditions for the 20 target chemicals.Chemical Sorbent Elution Solvent ProcedureCN AEX 0.01M HNO3 Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.4 mL of 0.01 M HNO3CSPS ENVI- MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOH CARBMPA mixed mode 0.01M HCl in MeOH Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.4 mL of 0.01M (C8+AEX) HCl in MeOHDIASH C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHEMPA AEX 0.01 M NaCl Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.3 mL of 0.01 M NaClIMPA AEX 0.01 M NaCl Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.3 mL of 0.01 M NaClCMPA AEX 0.01 M NaCl Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.3 mL of 0.01 M NaClPMPA AEX 0.01 M NaCl Load 50 mL sample at 0.5mL/min, wash sorbent with water, elute with 0.3 mL of 0.01 M NaClCEES C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHCEMS C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHTDG DPA-6S MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHHEES C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHCP C18 DCM/MeOH (4:1v/v) Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of DCM/MeOH (4:1v/v)MP C18 DCM/MeOH (4:1v/v) Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of DCM/MeOH (4:1v/v)FON C18 DCM/MeOH (4:1v/v) Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of DCM/MeOH (4:1v/v)DS C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHDSSO C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHDCBA C8 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOH44DCBP C18 MeOH Load 50 mL sample at 1mL/min, wash sorbent with water, elute with 0.2 mL of MeOHAEX=anion-exchange, MeOH=methanol, C8=silica based reversed-phase packing with monomerically bonded octyl (9%) carbon load, DPA-6S=polyamide resin with reverse phase retention mechanism, C18= silica based reversed-phase packing with monomerically bonded octadecyl(18%) carbon load, DCM=dichloromethane.Figures 1.22 to 1.41 shows the stack plot of the SER spectra of the LMC obtained using the static, flow and theSPE/IEX methods, respectively. A A B B C CFig.1.22. LMC for CN obtained by A) static (100 ppb, Fig.1.23. LMC for CSPS obtained by A) static (10 ppb,chem.L2), B) flow (10 ppb, chem.L2), and C) SPE (10 chem.L6), B) flow (1000 ppb, chem.L2), and C) SPE (10ppb, chem.L2). Conditions: as in Fig.1.2. ppb, chem.L3). Conditions: as in Fig.1.2. 16
  17. 17. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B B C CFig.1.24. LMC for MPA obtained by A) static (10 ppb, Fig.1.25. LMC for DIASH obtained by A) static (1000 ppb,chem.L6), B) flow (100 ppb, chem.L3), and C) SPE (1 chem.L3), B) flow (10 ppb, chem.L3), and C) SPE (10 ppb,ppb, chem.L6). Conditions: as in Fig.1.2. chem.L3). Conditions: as in Fig.1.2. A A B B CFig.1.26. LMC for EMPA obtained by A) static (1000 ppb, Fig.1.27. LMC for IMPA obtained by A) static (100 ppm,chem.L3), B) flow (1000 ppb, chem.L3), and C) SPE (10 chem.L3), and B) SPE (10 ppb, chem.L3). Conditions: asppb, chem.L3). Conditions: as in Fig.1.2. in Fig.1.2. NOTE: No SERS from flowing 1 ppm. A A B BFig.1.28. LMC for CMPA obtained by A) static (100 ppm, Fig.1.29. LMC for PMPA obtained by A) static (10 ppm,chem.L3), and B) SPE (10 ppb, chem.L2). Conditions: as in chem.L3_PDMS), and B) SPE (10 ppb, chem.L2).Fig.1.2. NOTE: No SERS from flowing 1 ppm. Conditions: as in Fig.1.2. NOTE: No SERS from flowing 1 ppm. 17
  18. 18. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B B C CFig.1.30. LMC for CEES obtained by A) static (1000 ppb, Fig.1.31. LMC for CEMS obtained by A) static (1000 ppb,chem.L4), B) flow (50 ppb, chem.L4), and C) SPE (10 ppb, chem.L4), B) flow (500 ppb, chem.L3), and C) SPE (10chem.L1). Conditions: as in Fig.1.2. ppb, chem.L2). Conditions: as in Fig.1.2. A A B B C CFig.1.32. LMC for TDG obtained by A) static (10 ppm, Fig.1.33. LMC for HEES obtained by A) static (100chem.L1), B) flow (1 ppm, chem.L1), and C) SPE (10 ppm, chem.L3), B) flow (1 ppm, chem.L2), and C) SPEppb, chem.L1_PEG). Conditions: as in Fig.1.2. (10 ppb, chem.L6). Conditions: as in Fig.1.2. A A B B C CFig.1.34. LMC for CP obtained by A) static (10 ppm, Fig.1.35. LMC for MP obtained by A) static (1 ppm,chem.L3), B) flow (1 ppm, chem.L3), and C) SPE (10 chem.L6), B) flow (1 ppm, chem.L2), and C) SPE (10 ppb,ppb, chem.L3). Conditions: as in Fig.1.2. chem.L3). Conditions: as in Fig.1.2. 18
  19. 19. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B B C CFig.1.36. LMC for FON obtained by A) static (1 ppm, Fig.1.37. LMC for DS obtained by A) static (100 ppm,chem.L2), B) flow (500 ppb, chem.L3), and C) SPE (10 chem.L6), B) flow (1 ppm, chem.L3), and C) SPE (10ppb, chem.L3). Conditions: as in Fig.1.2. ppb, chem.L2). Conditions: as in Fig.1.2. A A B C BFig.1.38. LMC for DS-SO obtained by A) static (10 ppb, Fig.1.39. LMC for DMHTP obtained by A) static (1 ppm,chem.L6), B) flow (1 ppm, chem.L1_PEG), and C) SPE chem.L3), and B) SPE (10 ppb, chem.L3). Conditions: as in(10 ppb, chem.L6). Conditions: as in Fig.1.2. Fig.1.2. A A B B C CFig.1.40. LMC for 3,5-DCBA obtained by A) static (100 ppm, Fig.1.41. LMC for 4,4-DCBP obtained by A) static (10 ppb,chem.L6), B) flow (1 ppm, v), and C) SPE (10 ppb, chem.L2). chem.L4), B) flow (1 ppb, 4), and C) SPE (10 ppb, chem.L4).Conditions: as in Fig.1.2. Conditions: as in Fig.1.2.Task 1 Summary: Chem. L2, L3 and L6 are the universal chemistries for screening of the 20 target chemicals atnominal concentrations. Polymer modified chemistries provided some selectivity towards a few classes ofchemicals (e.g. L1_PEG was better for pesticides and L2_PEG was better for Blister and Blood agent simulants likeCEES, CEMS, TDG and CN). Although a few chemicals could be detected at 10 ppb using the static or the flowmethods, none of the modifications provided this detection limit for all the 20 target chemicals. To achieve thedesired sensitivity of 10 ppb, SPE or AIEX methods were necessary. SPE sorbents like C8 and C18 provided auniversal pre-concentration method for the purpose of detecting the various chemical, toxic industrial and pesticideagents of concern, while the AIEX sorbents provide for the pre-concentration of nerve agent hydrolysis products.In conclusion, all of the 20 target chemicals could be detected at 10 ppb using SPE/AIEX methods with sol-gelchemistries L2 and L6. 19
  20. 20. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010Task 2. Develop SER-active capillary durability. The overall objective of this task is to develop the SER-activecapillary fabrication procedure so that modest flow rates, pressure, and temperature can be used for extended periodsof time. This will be accomplished by investigated cure and coating procedures, and performing flow, pressure andtemperature tests.As part of this task, we performed studies to evaluate the stability and shelf-life of our SER active sol-gels. Theprimary issues that must be addressed include determining the optimal conditions (e.g. temperature, time) for curingspecific sol-gel chemistries, under what conditions can the sol-gels (e.g. in capillaries) be reduced and stored withminimal loss of performance (e.g. 3 months) and their resistance to degradation during sample flow. Preliminaryresults have indicated that a constant cure temperature (e.g. cure at 20-25°C for up to 24 hrs) with the sol-gel sensorsproperly sealed (to minimize solvent loss and subsequent drying out) is critical.We performed extensive durability studies on chem.L2, L3, and L6, the three universal chemistries determinedduring Task 1.A. chem.L6 Durability Studies: As described before chem.L6 is an open-tubular chemistry (OTC), where silvernanoparticles are embedded into a thin Si-alkoxide film functionalized on the internal glass capillary surface. Sincethe coating is thin, it was important to know if this open tubular format is durable during continuous water flow andhow frequently the substrates need to be replaced. Hence, to determine the optimum fabrication conditions formanufacturing durable chem.L6 OTCs we performed the following experiments.1. The durability of chem.L6 was demonstrated by flowing pure water for one hour (at 1 mL/min) using a peristaltic pump through such a coated capillary. This was followed by measuring a 0.1 mg/mL sample of MPA, which exhibited no apparent decrease in the SERS signal as compared to similar pre-flow control measurements (see Figure 2.1). A similar set of experiments were performed in which HPLC water was flowed through the standard chem.L6 coated capillaries for 1 and 2 hours prior to the introduction of analyte samples (at RT, 10 mL/min). After 1 hour of flowing pure water, a 1 ppm sample of MPA in HPLC water was drawn into this capillary and measured. No MPA signal was detected (see Figure 2.2). To verify if SER-activity was completely extinguished, a 1000 ppm sample was measured on this same capillary. Again no signal was observed. Flowing water through capillaries coated with chem.L6 at 10 mL/min eliminates the SERS response. A A B BFig.2.1. SERS of MPA at 0.1 mg/mL in HPLC water; A) Fig.2.2. SERS of MPA after flowing HPLC water at 10sample loaded and measured (static) after flowing 50 mL of mL/min for 1 hr on chem.L6A) 1 ppm and B) 1000 ppm.pure HPLC water at 1 mL/min, and B) sample loaded and Conditions: 80 mW, 785 nm, 1-min.measured (static) on a different capillary with no prior flowingof water. Conditions: OTC chem.L6 (APTMS based), 90mW, 785 nm, 1-min.2. We examined the shelf-life of chem.L6. Two batches of chem.L6 OTC capillaries (40 each) were made initially (1 week apart) using the standard procedure. All measurements (here and in Task 5) were performed on multiple capillaries (and 9 spots for each capillary). This allowed evaluating variations within capillaries, between capillaries, and batch-to-batch capillaries. For the shelf-life test, a 30-min reduction was applied to the sol-gel, water removed, and sealed with parafilm. Measurements were made on the first day, and then on the following 4th and 7th days. In each case, MPA at 1 ppm was used to test the response over time (see Figures 2.3-2.4). The results indicate that 1 ppm can still be detected at the 9 equidistant points along the sol-gel coated capillary after 7 days. However, the signal appears to start dropping off substantially after 2 days. 20
  21. 21. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A B CFig.2.3. SERS of MPA at 1 ppm on chem.L6, 9-points, which Fig.2.4. SERS of MPA at 1 ppm on chem.L6, for the averagedwas parafilmed and capped for 7 days. Conditions: in water, 9-point spectra: aged A) 1 (red), B) 4 (black), and C) 7 days785 nm, 80 mw, 1-min (batch 1). (blue); 785 nm, 80 mw, 1-min (batch 1).3. We examined the sol-gel curing process as a function of both temperature and time in our continuing effort to further improve the overall performance (sensitivity, reproducibility and durability) of chem.L6 capillaries. Initial test were carried out on capillaries prepared as above with the exception that after curing for 24-hrs at RT, 4 of the chem.L6 capillaries were placed in a preheated oven set at 35 °C. A single capillary was removed after heating for a period of 10, 30, 60 or 180-min, respectively, which was allowed to cool to room temperature for 45-min, and then reduced (30-min) by the standard method. In each case, MPA at 1 ppm was used to test the response. The 9-point averaged SER spectra obtained for each capillary heated for the specified time at 35 °C are presented in Figure 2.5. This experiment was repeated on a different set of 4 capillaries at 50 °C (see Figure 2.6), and again at 65 °C (see Figure 2.7). These results are summarized in Figure 2.8 where the intensity of the 759 cm-1 peak (9 points averaged) is plotted for each temperature as a function of time. Two additional experiments were carried out at 35 °C and 50 °C. In these 2 cases, the capillaries were reduced first then heated. These results are also shown in Figures 2.9-2.10. Capillaries coated with chem.L6 1) heated for 10-min at 35 °C afforded an improvement in sensitivity by a factor of ~2 times that of the standard RT base-line response of 1 ppm MPA (this was confirmed in repeat measurements), and 2) extended heating over time (greater than 10-min) or at elevated temperatures (e.g. 50 °C) diminished the SERS response. It is important to point out that degradation generated artifacts in the spectra at 65 °C, which greatly enhanced the MPA signal over time. Although improvements were observed for some higher cure temperatures and periods, the improvements were not consistent, nor were they substantially better than RT cure. Since the RT conditions gave consistent results, they were used. A Fig.2.5. SERS of MPA at 1 ppm on chem.L6 (9 point B average), cured at 35 oC for A) 10, B) 30, C) 60, and D) 180- min. Conditions: in HPLC water, 80 mW, 785 nm, 1-min. C D 21
  22. 22. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A A B B C C D D Fig.2.6. SERS of MPA at 1 ppm on chem.L6 (9 point Fig.2.7. SERS of MPA at 1 ppm on chem.L6 (9 point average), cured at 50 oC for A) 10, B) 30, C) 60, and D) 180- average), cured at 65 oC for A) 10, B) 30, C) 60, and D) 180- min. Conditions: in HPLC water, 80 mW, 785 nm, 1-min. min. Conditions: in HPLC water, 80 mW, 785 nm, 1-min. 0.12 50 C 0.1 35 C 65 C 0.08 Peak Height 35 C Red 0.06 50 C Red 0.04 0.02 0 0 50 100 150 200 Curing time (min) Fig.2.8. Intensity of the peak at 759 cm-1 (baseline at 720 cm-1 subtracted) of MPA at 1 ppm as a function of curing time on chem.L6 (9 point average), at different curing temperatures 35 oC, 50 oC, and 65 oC. Conditions: 80 mW, 785 nm, 1-min. A A B C B D Fig.2.9. SERS of MPA at 1 ppm on chem.L6 (9 point Fig.2.10. SERS of MPA at 1 ppm on chem.L6 (9 point average), reduced then cured at 35o C for A) 10 and B) average), reduced then cured at 50o C for A) 10, B) 30, 30-min. Conditions: 80 mW, 785 nm, 1-min. C) 60, and D) 180-min. Conditions: 80 mW, 785 nm, 1- min.4. In order to determine the operational range of the chem.L6 capillaries, a temperature bath was used to set the temperature of aqueous samples of MPA, drawn through a capillary and measured. The analyte samples were measured at 20 and 40 °C (Figure 2.11). The response did not appear affected at 40 °C. 22
  23. 23. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 A Fig.2.11. SERS of MPA (static)1 ppm in HPLC water, with sample at A) 20 °C and B) 40 °C. Conditions: 80 mW, 785 nm, 1-min. B5. We continued to evaluate the shelf-life of our standard chem.L6 capillaries by investigating the optimum storage conditions. Three methods for storing these capillaries were investigated. A) Initially, a 30-min addition of Ag-colloids was applied to the sol-gel, water removed, and the capillary ends sealed with parafilm. The results indicate that 1 ppm MPA can still be detected at 9 equidistant points along the sol-gel coated capillary after 7 days (Figure 2.12), but exhibited no activity after 14 days. B) A similar experiment was also performed, but in this case water was added to the capillary prior to sealing. The activity is significantly diminished on the 4th day, and completely gone on the 7th day (Figure 2.13). C) A 3rd experiment was carried out where the APTES coating solution was removed after 24-hr, and then the capillaries sealed. After 7 days, the standard method for adding the Ag-colloids to the sol-gel coat was followed. SER-activity for MPA at 1 ppm was still observed (Figure 2.14). It is worth pointing out that the initial chem.L6 vials, which can be prepared and ready for measurement within 24-hrs, is still capable of detecting 250 ppb MPA even after 4 days of storage (see Figure 2.15). A A B B CFig.2.12. SERS of MPA on chem.L6 at 1 ppm after A) 1, B) 4 Fig.2.13. SERS of MPA on chem.L6 at 1 ppm after A) 4, andand C) 7 days, sealed with no water following Ag-colloid B) 7 days, sealed with water following Ag-colloid addition.addition. Conditions: HPLC water, 80 mW, 785 nm, 1-min. Conditions: HPLC water, 80 mW, 785 nm, 1-min. A BFig.2.14. SERS of MPA on chem.L6 at 1 ppm after coating Fig.2.15. SERS of MPA on chem.L6 coated vials at 250 ppbstep, sealed empty for 7 days, then Ag-colloids added, and after 4 days, A) single spot and B) 9 points averaged. Coatedtested at 9 spots. Conditions: HPLC water, 80 mW, 785 nm, 1- with 1% APTES for 24-hr, Ag-colloids added for 1-min, sealedmin. empty, tested 4 days later. Conditions: HPLC water, 80 mW, 785 nm, 1-min. 23
  24. 24. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 20106. Finally, we evaluated the shelf-life of our new chem.L6 vials (Figures 2.16-2.19), which were sent to the ECBC facilities at Aberdeen for preliminary testing as part of Task 7. Our preliminary results show that if Ag-colloid solution is added immediately following the APTES coating procedure, then sealed and stored empty, MPA can be detected at 25 ppb if measured on the first day (Figure 2.17A), at 250 ppb after being stored for 1-2 days (Figure 2.17B), and at 1 ppm following 7 days of storage (see Figure 2.18). It is worth pointing out that a very weak signal was observed sporadically for MPA at 1 ppm after 10 days of storage. However, as shown by the SERS of MPA at 250 ppb (Figure 2.19B) obtained with coated vials stored empty for 7 days, adding the Ag- colloids prior to making a measurement is the best method for maintaining sensitivity. A A B BFig.2.16. Images of A) standard chem.L1 coated vials (left: Fig.2.17. SERS of MPA on chem.L6 coated vials at A) 25 ppb 1stAg-TMOS sol-gel unreduced, right: after reduction) as day and B) 250 ppb 2nd day; after spin coated with 1% APTES forcompared to B) chem.L6 coated vials (left: after APTES 1-min (1400 rpm), then Ag-colloids added for 1-min (spinning atcoating, right: after silver colloids added). 1400 rpm), sealed empty. Conditions: HPLC water, 80 mW, 785 nm, 1-min. A BFig.2.18. SERS of MPA on chem.L6 coated vials, 1 ppm (on Fig.2.19. SERS of MPA on chem.L6 coated vials at A) 1 ppm2 spots); after spin coated with 1% APTES for 1-min (1400 and B) 250 ppb; after 1-min spin coating step (1400 rpm),rpm), then Ag-colloids added for 1-min (spin at 1400 rpm), sealed empty for 7 days, then Ag-colloids added for 1-minsealed empty for 7 days, and then measured. Conditions: as in (spin at 1400 rpm). Conditions: as in Fig.2.17. Note 889 andFig.2.17. 1418 cm-1 peaks indicate degradation of the APTES/colloid.Summary for the durability studies of chem.L6:1. The shelf-life of chem.L6 standard capillaries was found to be 1 week, though the signal started to drop off substantially after 2 days (Figures 2.1-2.3).2. Capillaries coated with chem.L6 1) heated for 10-min at 35 °C afforded an improvement in sensitivity by a factor of ~2 times that of the standard RT base-line response, and 2) extended heating over time (greater than 10-min) or at elevated temperatures (e.g. 50 °C) diminished the SERS response. Signal improvements were observed at further elevated cure temperatures (e.g. 65°C) and extended heating (greater than 60-min) but it also produced degradation (of sol-gel) generated artifacts in the spectra (Figures 2.5-2.8). Although improvements were observed for some higher cure temperatures and periods, the improvements were not consistent, nor were they substantially better than RT cure. Since the RT conditions gave consistent results, they were used.3. Flowing water through capillaries coated with chem.L6 at 1 mL/min did not affect the SERS response, whereas at 10 mL/min the response was eliminated (Figures 2.1 and 2.2). However none of these sol-gels became 24
  25. 25. “sf” RTA P2005#84 EPA SBIR Phase II CN: EP-D-06-084 Phase II Final Report May 2010 detached.4. Storing the chem.L6 capillaries without any solvent and sealed with parafilm gave better shelf life 7 days compared to those stored in water (signal seen after 4 days no signal seen on the 7th day- Figures 2.12-2.13).5. Initial results suggest that chem.L6 vials, which can be prepared and ready for measurement within 24-hrs, is capable of detecting 250 ppb MPA even after 4 days of storage (see Figure 2.15).6. For chem.L6 vials, our preliminary results show that if a Ag-colloid solution is added immediately following the APTES coating procedure, then sealed and stored empty, MPA can be detected at 25 ppb if measured on the first day (Figure 2.17A), at 250 ppb after being stored for 1-2 days (Figure 2.17B), and at 1 ppm following 7 days of storage (see Figure 2.18). It is worth pointing out that a very weak signal was observed sporadically for MPA at 1 ppm after 10 days of storage. However, as shown by the SERS of MPA at 250 ppb (Figures 2.14 and 2.19B) obtained with chem.L6 coated capillaries and vials stored empty, the best way to prolong the life of chem.L6 substrates is to store the APTEOS functionalized substrates (capillaries and vials) sealed and add silver colloid prior to making a measurement.B. chem.L3 Durability Studies:1. We examined the sol-gel curing process as a function of both temperature and time in our continuing efforts to improve the overall performance (sensitivity, reproducibility and durability) of sol-gel plugs in “packed” capillaries filled with chem.L3 and its variations of (e.g. chem.L32). We prepared chem.L3 and chem.L32 filled capillaries, allowed them to gel over night (24-hrs at RT), and then placed them into a pre-heated oven set initially at 40 °C for 10-min. Following this, the capillaries were taken out of the oven, allowed to equilibrate to RT for ~30-min, then reduced by the standard method, and tested for SER-activity (static) with FON at 1 ppm in HPLC water. In both instances, no SER-activity was observed (see Figure 2.20).2. In a second set of experiments, we prepared chem.L3 and chem.L32 filled capillaries, and immediately placed part of them into a pre-heated oven set initially at 26 °C and the rest in a refrigerator, for overnight curing. Following this, the two different sets of capillaries were taken out, allowed to equilibrate to RT for ~30-min, then reduced by the standard method, and tested for SER-activity (static) with FON at 1 ppm in HPLC water. For each case, SER-activity was observed (see Figure 2.21). An important observation was that all of the sol- gels cured at 26 °C formed “half-filled” capillaries similar to that of chem.2c. Such a capillary format is generally more reproducible than the standard filled format, but unfortunately is not as amenable to analyte pre- concentration by the continuous flow method. A A B BFig.2.20. SERS of FON, on A) chem.L3, and B) chem.L32 Fig.2.21. SERS of FON, on chem.L3 initially cured overnightafter curing 24-hrs at RT, heated at 40 °C for 10-min, in A) oven at 26 °C, and B) refrigerator at 4 °C. Conditions: 1equilibrated, reduced, and tested. Conditions: 1 ppm in HPLC ppm in HPLC water, 80 mW, 785 nm, 1-min (see Fig.2.20).water, 80 mW, 785 nm, 1-min.3. To investigate the durability of the capillaries, experiments were also performed in which HPLC water (at RT) was flowed continuously at a rate of 5 mL/min using a peristaltic pump through a standard series of reduced chem2d capillaries for 1, 2 and 5 hours prior to the introduction of an analyte sample (see Figure 2.22). The 3 point averaged “static” spectra of FON (10 ppm in HPLC water) following flow of water for 2-hr (Fig.2.22A) and 5-hr (Fig.2.22B) are nearly identical.4. A similar experiment was then carried out on a second set of chem.L3 capillaries, where ordinary tap water was continuously flowed through the reduced sol-gels (at RT, and 5 mL/min) for 24-hrs. None of these sol-gels became detached or appeared bleached out. The subsequent addition of a 10 ppm FON sample revealed that SER-activity was retained after 24-hrs of flowing just water (Fig.2.22C), but the signal was relatively weak. 25

×