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Spotlight on Analytical Applications Complete e-Zine - Volume 3


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This document provides key analytical applications to help laboratories address the pressing concerns of the changing global landscape. Specifically, Volume 3 includes applications for Energy, Environmental, Food & Beverage, and Pharmaceuticals & Nutraceuticals.

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Spotlight on Analytical Applications Complete e-Zine - Volume 3

  2. 2. INTRODUCTIONPerkinElmer Spotlight on Applications e-Zine – Volume 3PerkinElmer knows that the right training, methods, applications, reporting andsupport are as integral to getting answers as the instrumentation. That’s whyPerkinElmer has developed a novel approach to meet the challenges that today’slabs face – that approach is called EcoAnalytix™, delivering to you completesolutions for your applications challenges.In this effort, we are pleased to share with you our Spotlight on Applicationse-zine, delivering a variety of topics that address the pressing issues and analysischallenges you may face in your application areas today.Our Spotlight on Applications e-zine consists of a broad range of applicationsyou’ll be able to access at your convenience. Each application in the table of contentsincludes an embedded link that will bring you directly to the appropriate pagewithin the e-zine.PerkinElmer
  3. 3. CONTENTSEnergy• Determination of Methanol in Crude Oils According to ASTM D7059-04 Using the Clarus 680 GC with S-Swafer Micro-Channel Flow Technology• Determination of Low-Level Oxygenated Compounds in Gasoline Using the Clarus 680 GC with S-Swafer Micro-Channel Flow Technology• Fatty Acid Methyl Ester Contamination of Aviation Fuel by GC/MS• Curing Determination of EVA for Solar Panel Application by DSCEnvironmental• Determination of Mercury in Wastewater by Inductively Coupled Plasma-Mass Spectrometry• Qualitative Analysis of Evolved Gases in Thermogravimetry by Gas Chromatography/Mass SpectrometryFood & Beverage• The Determination of Metals in Dietary Supplements• Solid Phase Extraction and GC/MS Analysis of Melamine Adulteration in Dairy ProductsPharmaceuticals & Nutraceuticals• Fast Analysis of Fat-Soluble Vitamins Using Flexar FX-10 UHPLC and Chromera CDS• Assuring Safety of Traditional Chinese Herbal Medicines by Monitoring Inorganic Impurities using ICP-MS• Polymorphism in Acetaminophen Studied by Simultaneous DSC and Raman Spectroscopy• Pressure-Balanced Headspace for the Determination of Class I, II and III Residual Solvents in Pharmaceuticals by USP Chapter <467> Methodology PerkinElmer
  4. 4. a p p l i c at i o n n o t e Gas Chromatography Author Andrew Tipler PerkinElmer, Inc. Shelton, CT 06484 USADetermination of Introduction The gas chromatographic (GC) analysis of crude oilMethanol in Crude Oils is a challenging undertaking. Samples are viscous, making them difficult to handle, and they containAccording to ASTM hundreds of different compounds with carbon numbers up to or even above C120, making a completeD7059-04 Using the chromatographic separation effectively impossible.Clarus 680 GC with ASTM® D7059-04 is an established method that has been well validated for the determination of methanolS-Swafer Micro- in crude oils. The method lists five variants of the instru- mentation that have demonstrated compliance withChannel Flow this method. The method also allows for alternativeTechnology configurations that will meet the required performance criteria. In this application note, a method based on a PerkinElmer® Clarus® 680 GC with an S-Swafer™ micro-channel flow splitting device is described; the data presented here will demonstrate that this method complies with the requirements of ASTM® D7059-04.
  5. 5. Experimental will enter the first column, leaving the heavier crude-oil The Clarus 680 GC used in this application note is described compounds in the liner. The two alcohols enter the first in Figure 1 with a diagram, and Figure 2 with a photograph non-polar column and elute early in the chromatography. of the S-Swafer micro-channel flow splitting device used to A chromatogram of a standard mixture is shown in Figure 3. perform this analysis. This two-column backflushing configura- tion (designated as S6 in the Swafer documentation) enables the first column to be backflushed while the analytes are still being chromatographed on the second column. A restrictor tube is also connected to one of the S-Swafer outlets to enable the carrier-gas flow rate to be increased and to allow the chromatography to be monitored on the first column by connecting the restrictor outlet to the FID. Nitrogen is used as the carrier gas throughout this application – it is well suited for use with 0.530 mm i.d. columns. Nitrogen, when compared to helium, is less expensive, more available, and not in limited supply. The use of nitrogen is consistent with PerkinElmer initiatives to reduce the use of the declining global stocks of helium. Figure 3. Chromatogram of standard mixture on first column with the The crude-oil sample is diluted 50:50 with clean toluene restrictor tube connected to the FID. solvent containing 1-propanol internal standard to produce a final concentration of 500 ppm. 1.0 µL of the diluted sample is injected into the programmable split/splitless (PSS) From Figure 3, it can be seen that the last peak of interest, injector which has the liner temperature set to 125 °C. the 1-propanol internal standard, elutes at about 3.2 minutes. At this temperature, only the volatile fraction of the sample Anything that elutes later than this time is of no analytical interest and backflushing should commence soon after elution of the 1-propanol peak – in this case 3.3 minutes. The backflushing process occurs when the pressure at the column inlet is less than that at the column outlet. This can be achieved by reducing the first-column inlet pressure at the PSS injector, increasing the (midpoint) pressure at the S-Swafer or doing both. In this analysis, we want to continue chromatography on the second column while we backflush the first column so the only option is to reduce the pressure at the injector. To enable a large backpressure to be used, the second column has an inline restrictor Figure 1. The S-Swafer system used to determine methanol in crude oil. connected between it and the S-Swafer. This enables the midpoint pressure to be increased, yet still allows reasonable flow rates to be applied to the second column. The reduction in the inlet pressure is affected through the use of a simple GC timed event. When the backflushing commences after a crude-oil sample has been injected, the heavier fraction of the sample will still reside within the injector liner which has been held at 125 °C. At this point, the PSS liner is temperature programmed to a high temperature to vaporize this less-volatile material. Because the column is being backflushed, none of this vapor will enter the column, but will be flushed out of the system through the split vent. In this way, removal of the heavy compounds is very efficient and doesn’t expose the columns to this material, thus prolonging the column life. Figure 2. Photograph of installed system showing the S-Swafer connections.2
  6. 6. Figure 4 shows a chromatogram of a standard solution on the backflushed until the oven reaches its initial programmedfirst column with backflushing applied at 3.3 minutes. The temperature. The initial split-flow rate is set to 100 mL/minchromatography is now very clean beyond the 1-propanol peak. to ensure that the pre-run pressure change equilibrates quickly. The split flow is reset to 10 mL/min by a pre-run event at -0.50 minutes, which occurs once the pressure has stabilized. These split-flow changes serve only to save time. Table 1. Analytical Conditions for the Determination of Methanol in Crude Oil. Gas Chromatograph PerkinElmer Clarus 680 GC Oven Temperature 125 °C for 1 minute, then 25 °C/min to 250 °C Injector Programmable Split/Splitless (PSS) Injector Temperature 125 °C for 3.3 minutes, then 200 °C/min to 400 °C and hold until the end of the run Carrier Gas NitrogenFigure 4. Chromatogram of standard mixture on first column with backflushing Initial Injector Pressureat 3.3 minutes with the restrictor tube connected to the FID. Setpoint 2 psig (see text) Initial Injector SplitFigure 5 shows chromatograms from the CP-Lowox column ® Flow Rate 100 mL/min (see text)of three calibration mixtures that cover the calibration range Detector Flame Ionization (FID)of this method. Again, the chromatography looks very clean. Detector Temperature 325 °C Detector Combustion Gases Air: 450 mL/min, Hydrogen: 45 mL/min Detector Range x1 Detector Attenuation x4 Backflush System S-Swafer configured in S6 mode Precolumn 30 m x 0.530 mm x 5 µm PerkinElmer Elite™ 1 with 25 cm x 0.250 mm deactivated fused silica restrictor connected between S-Swafer and column Analytical Column 10 m x 0.530 mm x 10 µm Varian® CP-Lowox® with in-line 25 cm x 0.100 µm deactivated fused silica restrictor connected between S-Swafer and column Restrictor TubingFigure 5. Chromatography of three methanol standard solutions containing between S-Swafer~500 ppm w/w 1-propanol internal standard. and Detector 30 cm x 0.100 µm deactivated fused silica (Midpoint) PressureThe full method for this analysis is given in Table 1. The use at S-Swafer 20 psigof timed events in this method needs explanation. The GC Timed Events (see text) PSS pressure set to 24 psig at -1.00 minoven needs to be programmed up to 250 °C in order to PSS split flow set to 10 mL/min at -0.50 minelute the analytes from the CP-Lowox® column. At this PSS pressure set to 2 psig at 3.30 mintemperature, there is some slight stationary-phase bleed from PSS split flow set to 100 mL/min at 3.31 minthe thick-film methyl silicone precolumn. The precolumnremains in the backflush mode during cooling to prevent any Sample Preparation 5 g of crude-oil sample mixed with 5 g of toluene containing 1-propanol internalof the bleed from the precolumn at the onset of cooling from standard to deliver a final concentrationentering the CP-Lowox® column. The initial injector pressure of 500 ppm w/wof 2 psig and the pre-run timed event to set the pressure Sample Injection Normal injection of 1.0 µL of preparedto 24 psig at -1.00 minutes ensures that the pre-column is sample using an autosampler 3
  7. 7. Discussion What should also be noted is that the total chromatography The calibration plot obtained for the mixtures of methanol time is just six minutes. For most of this time, the injector and 1-propanol in toluene are shown in Figure 6. This plot liner is being heated at a high temperature and the precolumn demonstrates good linearity which is in compliance with is being backflushed at a very high flow rate, while the oven ASTM® D7059. is being temperature programmed. This means that, at the end of the run, all of the less-volatile sample compounds have been flushed from the system. All that is then necessary is to cool the oven, reset the inlet pressure and inject the next sample. The Clarus 680 GC used for this analysis has rapid oven cooling and starts to load the autosampler with sample prior to the GC coming ready and so sample throughput exceeds six samples per hour. Table 2 shows the quantitative precision obtained from ten replicate injections of a high-level and a low-level check standard. Considering the complexity of the sample matrix, these results demonstrate the efficacy of the Swafer tech- nology for this type of application. These results greatly exceed the requirements of ASTM® D7059. Figure 6. Calibration plot showing response ratio vs. amount ratio for methanol:1-propanol internal standard. Table 2. Quantitative precision of low-level and high-level check standards prepared using a sample of light crude oil. Figure 7 shows a chromatogram of a low-level check standard Run Results for Results for prepared from a sample of light crude oil. The hydrocarbons Check Standard A Check Standard B that elute with the alcohols into the second column before 28.2 ppm w/w 1096 ppm w/w backflushing is initiated are lightly retained on the CP-Lowox® 1 33.2 1063 column and so quickly elute in the chromatography. The 2 32.2 1063 alcohols are much more strongly retained and require an extended temperature program to elute and are well separated 3 32.7 1065 from the light hydrocarbons in the crude oil. Note the clean 4 32.6 1059 baseline around the alcohols, which facilitates precise quan- 5 32.9 1059 tification. 6 35.6 1062 7 33.4 1065 8 33.9 1068 9 33.6 1061 10 33.8 1064 Relative Std Dev % 2.88 0.26 The analytical system was validated using a set of 20 ‘round- robin’ samples prepared by Spectrum Analytical Standards, Sugarland, Texas. These are shown in Figure 8. These sam- ples were prepared five years ago to validate the published ASTM® D7059-04 method. It is believed that these samples are stable and would provide a good basis for validating this Figure 7. Chromatogram of 25 ppm w/w check standard prepared in a sample Swafer system for compliance with the ASTM® method. of light crude oil.4
  8. 8. One of the concerns regarding the GC analysis of crude oil is that non-volatile sample residue will accumulate in the system giving rise to adsorption, thermolysis or carryover effects. This method uses a combination of low injection temperature and column backflushing to keep heavier sample compounds out of the columns. Figure 9 shows the chromatography of crude-oil samples soon after a new liner and septum have been installed compared against the chro- matography after over 150 crude-oil injections have been made into the same liner and septum. Clearly, sample residue will accumulate as the number of injections increases (particu- larly with heavy crude oils) and eventually the liner and the septum will need to be changed. Figure 9 shows that after 150 injections, this method continues to perform.Figure 8. ASTM® D7059 round-robin validation samples.Table 3 summarizes the results from the round-robin sampleset. All are within the ASTM® D7059 limits except the resultfor Sample 19, which is just outside the accepted range.Given the age of these samples, these results are consideredacceptable, and the method does tolerate one result deviationout of twenty. Table 3. Results obtained for ASTM® D7059 round-robin validation samples. Sample Experimental Expected 1 2.0 2.7 Figure 9. Chromatograms of the same crude-oil sample spiked with 400 ppm 2 4.3 5.8 w/w methanol produced using a single injector liner showing no significant degradation in chromatography after over 150 runs. 3 7.4 11.7 4 11.4 14.9 5 7.8 12.9 6 29.8 35.1 7 23.8 27.6 8 31.2 35.7 9 58.1 66.3 10 60.4 67.0 11 69.5 74.5 12 105.5 113.4 13 113.4 133.2 14 265.3 285.2 15 393.8 404.7 16 542.8 592.9 17 596.3 524.2 18 873.2 912.2 19 739.8 826.5 20 709.9 734.7 5
  9. 9. ConclusionThis method, based on the S-Swafer technology, fullycomplies with the requirements of ASTM® D7059-04 andoffers the user a number of unique benefits:• The method presented here will provide very high throughput and fast delivery of results; with a complete analysis cycle time less than ten minutes per sample (more than six samples/hour throughput)• Reduced instrument maintenance as a result of temperature- programmed injection which prevents heavy sample compounds from entering and degrading columns• Additional protection of the analytical columns and reduction of run time with the use of backflushing• Single-detector configuration simplifies and reduces the cost of the system• Splitting restrictor enables precolumn chromatography to be monitored, facilitating the setup of backflush timing• Nitrogen carrier gas reduces costs associated with carrier gas and serves to help preserve helium stocks• Quantitative performance exceeding the method specification delivers results that will meet laboratory quality-control specifications.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2010, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.009027A_01
  10. 10. a p p l i c at i o n n o t e Gas Chromatography Author Andrew Tipler PerkinElmer, Inc. Shelton, CT 06484 USADetermination of Introduction The existing ASTM® D4815 method is designed to monitorLow-Level Oxygenated oxygenated compounds in gasoline at percentage concen- trations. The method described in this application note isCompounds in Gasoline intended to enable these analytes to be monitored down toUsing the Clarus 680 GC low-ppm concentrations. There is an increased need to monitor the level of oxygen-with S-Swafer Micro- ates in reformulated gasoline because of the increased risk of contamination from more abundantly available biofuels.Channel Flow Technology Gasoline contamination with oxygenated compounds can lead to more toxic carbonyl emissions into the atmosphere from engines running the fuel. Contamination of feedstocks with oxygenated compounds can cause degradation of expensive catalysts and impact the refining process.
  11. 11. The analytes targeted in this method are those specified in ASTM® D4815 and are given in Table 1. Table 1. Targeted Oxygenated Compounds. Methanol Ethanol Isopropanol tert-Butanol n-Propanol Methyl tert-butyl ether (MTBE) sec-Butanol Figure 1. Diagram of the S-Swafer micro-channel flow technology used to determine trace-level oxygenated compounds in gasoline. Diisopropyl ether (DIPE) Isobutanol Ethyl tert-butyl ether (ETBE) to one of the S-Swafer outlets to enable the carrier-gas flow tert-Pentanol rate to be increased and to allow the chromatography to be 1,2-Dimethoxyethane monitored on the first column by connecting the restrictor outlet to the FID. Note the use of nitrogen as the carrier gas. n-Butanol This carrier gas is well suited to 0.530 mm i.d. columns and tert-Amyl methyl ether (TAME) is consistent with initiatives to reduce the use of the declining global stocks of helium. Experimental The experimental details for this analysis are given in Table 2. Figure 1 shows a diagram of the S-Swafer™ micro-channel The sample of gasoline is injected and chromatographed on flow splitting device used to perform this analysis. This two- the non-polar precolumn. The polar oxygenated compounds column backflushing configuration (designated as S6 in the are quick to elute into the second CP-Lowox® column and Swafer documentation) enables the first column to be back- will precede the bulk of the gasoline hydrocarbons. Once flushed while the analytes are still being chromatographed the oxygenated compounds are in the second column, the on the second column. A restrictor tube is also connected first column is backflushed to remove the hydrocarbons Table 2. Analytical Conditions for the Determination of Trace-Level Oxygenated Compounds in Gasoline. Gas Chromatograph PerkinElmer® Clarus® 680 GC Analytical Column 10 m x 0.530 mm x 10 µm Varian® CP-Lowox® Oven Temperature 80 °C for 1 minute then 5 °C/min with in-line 25 cm x 0.100 µm deactivated to 125 °C then 10 °C/min to 230 °C fused silica restrictor connected between S-Swafer and column Injector Heated split/splitless Restrictor Tubing 30 cm x 0.100 µm deactivated fused silica Injector Temperature 250 °C between S-Swafer Carrier Gas Nitrogen and Detector Initial Injector Pressure 2.0 psig (see text) (Midpoint) Pressure 35 psig at S-Swafer Injector Split-Flow Rate 15 mL/min Timed Events Carrier gas pressure set to 45 psig at -1.00 min Detector Flame Ionization (FID) (see text) Carrier gas pressure set to 2 psig at 1.52 min Detector Temperature 325 °C Sample Preparation a) AccuStandard® 4815-RT-PAK diluted Detector Combustion Gases Air: 450 mL/min, ~1:1500 in washed gasoline to give 27.4 Hydrogen: 45 mL/min to 50 ppm w/w Detector Range x1 b) AccuStandard® 4815-RT-PAK diluted Detector Attenuation x4 ~1:7500 in washed gasoline to give 5.5 to 10 ppm w/w Backflush System S-Swafer configured in S6 mode Sample Injection Fast injection of 1.0 µL of prepared sample Precolumn 15 m x 0.530 mm x 1 µm PerkinElmer using an autosampler Elite™-1 with 25 cm x 0.250 mm deactivated fused silica restrictor connected between S-Swafer and column2
  12. 12. from the GC system. While the backflushing is in progress,the oxygenated compounds are chromatographed on thehighly polar CP-Lowox® column which easily separates themfrom any hydrocarbons that also enter the second column.Precolumn backflushing is initiated by a timed event at1.52 minutes that reduces the pressure inside the injectorto 2.0 psig so that carrier gas flows backwards. The inletpressure is set to 2.0 psig to maintain the backflushing ofthe precolumn during oven cooling. A pre-run timed eventsets the inlet pressure to 45 psig so that forward flow isrestored prior to injection of the sample.Figure 2 shows a chromatogram of gasoline on the pre-column with no backflushing. The oxygenated compoundswould elute within the first one or two minutes of this Figure 3. Precolumn chromatogram of a mixture of oxygenated compoundschromatogram and would be totally obscured by the early- at 4% to 7.3% w/w concentration indicating the proposed backflush point.eluting hydrocarbons in the gasoline. The later-eluting peaks Injector split flow increased to 100 mL/min.are not needed in this analysis so they will be the target ofthe backflushing step. Figure 4 shows the same sample run under the same conditions as those for Figure 3 but with the detector connected to the end of the analytical column. Good peak shapes and separations of the oxygenated compounds are seen within a 20.5-minute run time. On this column, some of the alcohol isomers are not separated. The total cycle time was about 25 minutes, which included oven cooldown and equilibration and autosampler loading.Figure 2. Chromatogram of 87-octane gasoline on the precolumn.Figure 3 shows a chromatogram of a mixture of the oxygenatedcompounds (no solvent) on the precolumn and it can beseen that all the peaks of interest have eluted from thiscolumn in just less than 1.50 minutes. From this trace, thebackflush point was chosen to be 1.52 minutes. Figure 4. Analytical column chromatogram of a mixture of oxygenated compounds at 4% to 7.3% w/w concentration with precolumn backflushing at 1.52 minutes. Injector split flow increased to 100 mL/min. 3
  13. 13. To test the system on samples of gasoline containing known The standard mixture of oxygenated compounds was diluted levels of oxygenated compounds, a quantity of gasoline was with the washed gasoline to produce low-level mixtures. ‘washed’ with water. 5 mL of 87-octane gasoline obtained These were chromatographed using the newly developed from a local filling station were shaken with 10 mL of deionized method and the chromatogram is shown in Figure 6. water for two minutes and then centrifuged at 5000 rpm for ten minutes. The aqueous layer was discarded and the process was repeated. 0.5 g of anhydrous sodium sulfate was added to the cleaned gasoline and shaken to remove any traces of water. Figure 5 shows chromatography of the gasoline before and after washing. Even though the gasoline contained up to 10% ethanol, this and all other polar compounds were effectively removed by the washing procedure. Figure 6. Chromatogram of washed gasoline spiked with low levels of oxygenated compounds. The 27.4 – 50 ppm w/w mixture was injected repeatedly to measure the area and retention-time precisions. These are summarized in Table 3. The area precision is around 1% relative standard deviation which is an excellent result – especially for polar compounds at low levels in a highly complex sample matrix like gasoline. The retention-time precision, which ranges from 0.013% to 0.039% relative standard deviation, is again an excellent result, considering the nature of this analysis. Figure 5. Efficacy of gasoline washing procedure for preparation of standard mixtures. Table 3. Area and Retention-Time Precision of a Standard Mixture of Oxygenated Compounds (n=9). Compound Conc. (ppm w/w) Mean Area RSD% Area Mean R.T (min) RSD% R.T. Ethyl tert-Butylether (ETBE) 27.4 64807 0.69 9.580 0.028 Methyl tert-Butylether (MTBE) 27.4 58557 0.64 9.827 0.021 Diisopropylether (DIPE) 27.4 53993 0.80 10.044 0.039 tert-Amylmethylether (TAME) 50.0 101209 0.65 11.503 0.039 Methanol 50.0 31028 1.11 13.642 0.023 Ethanol 50.0 60104 0.96 15.663 0.015 n & i-Propanol 50.0/50.0 142362 1.10 17.109 0.016 i, s & t-Butanol 50.0/50.0/50.0 273656 0.72 18.233 0.009 n-Butanol 50.0 89299 0.76 18.740 0.013 tert-Pentanol 50.0 103335 0.63 19.287 0.013 1,2-Dimethoxyethane 41.1 64233 1.26 19.982 0.0164
  14. 14. ConclusionThis method, based on the S-Swafer technology, is able toseparate and quantify the ASTM® D4815 target analytes atlow-ppm levels and offers the following user benefits:• High-throughput analysis, with a complete analysis cycle time of 25 minutes• A robust system – the analytical column is protected from most of the gasoline compounds by backflushing• In-line restrictor with secondary column allows the primary column to be backflushed during chromatography, reducing analysis time• Splitting restrictor enables precolumn chromatography to be monitored – facilitating system setup• Use of nitrogen carrier gas to help preserve helium stocks and reduce operating costs• Excellent quantitative precision.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2010, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.009033_01
  15. 15. a p p l i c at i o n n o t e Gas Chromatography/ Mass Spectrometry Author Greg Johnson PerkinElmer, Inc. Shelton, CT 06484 USAFatty Acid Methyl Introduction The contamination of aviation fuel with fatty acidEster Contamination of methyl esters (FAMEs) can arise due to the use of multi-product pipelines for fuel supply and distribution.Aviation Fuel by GC/MS In some countries, the widespread, mandatory intro- duction of automotive fuels with a bio-material content means that these pipelines are exposed to both auto- motive biodiesel with a 5% FAME (BD 5) content as well as to aviation fuel. FAMEs can adsorb onto the surface of the pipeline and later desorb, contaminating whatever fuel that follows, including aviation fuel. FAMEs alter the physical properties of the fuel. While presence of FAMEs in aviation fuel is of global concern, the United Kingdom is at the forefront of the analysis. The specification of aviation fuel in the UK is defined in the Ministry of Defence (MoD) Defence Standard 91-91. Technical authority for this standard is controlled by the MoD Defence Fuels Group with the agreement of the UK Civil Aviation Authority (CAA). This specification has recently been amended to formalize the acceptance of FAMEs in aviation fuel up to a maximum of 5 mg/Kg (ppm) combined total. To measure this specification, the Energy Institute has issued a method entitled IP PM DY: Determination of fatty acid methyl esters (FAME) derived from biodiesel fuel, in aviation turbine fuel – GC/MS with selective ion monitoring/scan detection method. The US specification of aviation fuel is covered by ASTM® D1655; in August of 2009, in a special airworthiness bulletin (NE-09-25R1), the Federal Aviation Administration (FAA) stated its intent to include a similar regulation in its specifications.
  16. 16. Current methods for determining FAME in aviation fuel use Table 1. Detailed instrument parameters for the GC/MS a polar ‘wax’ type GC column with mass spectrometry (MS) analysis of FAMEs. for detection. The polar column will be more retentive for GC Conditions FAME compounds relative to the less polar hydrocarbon Column 25 m x 0.32 mm id x 0.25 μm BPX70 compounds of the fuel. The MS will identify FAMEs based on unique spectral data, further distinguishing FAMEs from Injector Split/splitless @ 280 ˚C with glass wool packed hydrocarbon aviation fuel. The limitation of current methods liner is that the wax column has a relatively low maximum- Carrier Gas Helium @ 15 psig at injector and 3 psig at Swafer temperature limit and high column bleed as it approaches Injection 1.0 μL splitless for 0.75 minutes then 50 mL/min this limit. Oven 150 ˚C for 2 minutes then 10 ˚C/min to 220 ˚C and hold for 6 minutes MS Conditions Mode Electron Ionization (70 eV) Source 180 ˚C Transfer Line 300 ˚C Photomultiplier 550 V Table 2. Calibration summary for FAMEs with GC/MS. Figure 1. 0.1 ppm (wt/wt) individual FAME compounds in n-dodecane. FAME Concentration Range Coefficient of Determination (r2) C16:0 0.5 to 10.0 ppm 0.999929 In this application note, a different type of polar capillary C18:0 0.5 to 10.0 ppm 0.999872 column is used. This column reduces the temperature necessary to elute all compounds, while also providing a higher maxi- C18:1 0.5 to 10.0 ppm 0.999744 mum temperature. This will reduce both the wear on the C18:2 0.5 to 10.0 ppm 0.999577 column and the amount of signal in the chromatogram C18:3 0.5 to 10.0 ppm 0.999092 associated with column bleed. Additionally, this method will increase sample throughput. The specification of 5 mg/Kg is a total for all FAME compounds present and therefore the Calibration limit of detection for individual FAME compounds needs to A commercially available standard (Supelco®) containing be significantly lower than 5 mg/Kg. Figure 1 demonstrates equal masses of pure C16:0, C18:0, C18:1, C18:2 and that 0.1 mg/Kg is possible using this experimental setup. C18:3 was diluted by weight to 2000 mg/Kg with n-dodecane solvent, as recommended in Institute of Petroleum method Experimental PM-DY/09. Calibration standards were prepared at 0.5, 1.0, This application was performed on a PerkinElmer® Clarus® 2.5, 5.0 and 10.0 mg/Kg and spiked with 2.0 µL of C21:0 in 680 GC/MS with a capillary split/splitless injector. A 1.0 µL n-dodecane solution used as an internal standard. splitless injection was used to introduce the standards and samples into an unpacked, 2 mm i.d., quartz liner. The chro- matographic separation was achieved on a 25 m x 0.32 mm i.d. x 0.25 µm BPX70 column (SGE, Australia). The MS was used in single-ion-recording mode (SIR) to provide maximum sensitivity and specificity. Complete instrument parameters are presented in Table 1. Figure 2. The calibration result from TurboMass™ GC/MS software demonstrating the linear response of FAME C16:0 across a range of 0.5-10.0 mg/Kg.2
  17. 17. The calibration standards were analyzed in triplicate. All datapoints were used without exception. The response across the Table 5. The precision results from the analysis of a rapeseed oil mixture (n=10).calibration range was very linear (r2 > 0.9991) for all FAMEcompounds; complete calibration data is presented in Table 2. RSD%Additionally, Figure 3 demonstrates the calibration output RSD% Int’l Std. Conc. (%) in Conc. Absolute Responsefrom the PerkinElmer TurboMass software. FAME original mix (ppm) final Area RatioImmediately following the instrument calibration, a 5 mg/Kg C14:0 1.0 0.50 2.02 0.86standard was analyzed to provide additional precision data. C16:0 4.0 2.00 1.66 1.18The results of this precision study are reported in Table 3. C18:0 3.0 1.50 2.08 0.63 C18:1 60.0 30.00 1.52 0.54 Table 3. System precision evaluation, replicate injections C18:2 12.0 6.00 1.84 0.19 (n=15) of the 5.0 mg/Kg calibration mixture. C18:3 5.0 2.50 2.34 0.89 FAME Concentration RSD% Absolute RSD% IS Peak Area Resp. Ratio C20:0 3.0 1.50 2.08 0.33 C16:0 5.0 ppm 1.34 0.78 C20:1 1.0 0.50 3.41 1.71 C18:0 5.0 ppm 1.34 0.50 C22:0 3.0 1.50 2.83 1.10 C18:1 5.0 ppm 1.40 0.62 C22:1 5.0 2.50 3.04 1.53 C18:2 5.0 ppm 1.22 0.86 C24:0 3.0 1.50 3.66 1.86 C18:3 5.0 ppm 1.55 0.86 Internal Standard = C21:0The ability of the method to determine a wide range ofFAMEs at various concentrations was verified by analyzing acommercially available rapeseed oil standard (Supelco®). Thestandard was diluted 100 fold (100 mg to 10 g) by weightin n-dodecane, with a further 200:1 dilution resulting in amixture with the composition in Table 4. Table 4. Composition of fame mixture used to verify the method identification of a mixture of FAMEs. FAME Initial Concentration Final Concentration C14:0 1.0 % 0.5 ppm C16:0 4.0% 0.8 ppm C18:0 3.0% 0.6 ppm Figure 3. Chromatography of the rapeseed oil reference mixture using SIR. C18:1 60.0% 30.0 ppm C18:2 12.0% 6.0 ppm The final verification of this method was to analyze an C18:3 5.0% 2.5 ppm aviation-fuel sample spiked with a known amount of FAME. C20:0 3.0% 1.5 ppm Figure 4 presents the resultant chromatogram from the C20:1 1.0% 0.5 ppm analysis of an aviation-fuel sample spiked with between C22:0 3.0% 1.5 ppm 0.5 and 30 ppm FAME. C22:1 5.0% 2.5 ppm C24:0 3.0% 1.5 ppmThe rapeseed oil was analyzed in ten replicates to verify theprecision of the method when the FAME materials span awide concentration range (Table 5). An example chromatogramfrom this analysis is shown in Figure 3. 3
  18. 18. Figure 4. The resultant chromatogram of the analysis of aviation fuel spikedwith FAME.As you can see in Figure 4, the GC conditions provideadequate resolution of C16:0 FAME from the hydrocarbonenvelope of the aviation fuel, as well as low-level detectioncapabilities independent of matrix.ConclusionsThis application note demonstrated the use of the Clarus680 GC/MS to identify and determine the concentration oflow-level FAMEs. A polar column was used in conjunctionwith a short GC run to provide a fast and robust method.The MS was operated in SIR mode to achieve the highestlevels of sensitivity and specificity.Also demonstrated in this note is compliance with the newlyreleased methods set forth by regulatory agencies such asthe Institute of Petroleum. In addition, preliminary resultsindicate that the current method used for the analysis ofFAME contamination in aviation fuel can be speeded up verysignificantly without sacrificing either sensitivity or precision.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2010, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.009031_01
  19. 19. a p p l i c at i o n n o t e Differential Scanning Calorimetry Authors Ji-Tao Liu Tiffany Kang Peng Ye PerkinElmer, Inc. Shelton, CT 06484 USACuring Determination Introduction Renewable energy has attracted a lot ofof EVA for Solar Panel interest due to the limited supply of coal and oil and the environmental concernApplication by DSC of carbon dioxide (CO2) emission. There are many different forms of renewable (green) energy including: solar, wind, geothermal, biomass, and so on. Among them, solar energy is the fastest-growing segment. Increasing manufacturing capacity and decreasing product costs have led to significant growth in the solar industry over the past several years. For instance, solar photovoltaic (PV) production has been increasing by an average of 48% each year since 2002. By the end of 2008, the cumulative PV installation reached more than 15 giga-watts globally. A solar cell is a device that can convert sunlight directly into electricity. Different solar-cell technologies including crystalline silicon, organic photovoltaics, and dye-sensitized solar cells have been developed for various solar-cell applications. Currently, the most widely commercially available solar cell is based on crystalline- silicon technology. This technology is mature compared with the other solar-cell technologies and its energy-conversion efficiency is high.
  20. 20. A photovoltaic module or system consists of many jointly Experimental connected solar cells. The solar cells are packaged between The instrument used here is the PerkinElmer® double-furnace a backsheet on the bottom and a tempered-glass window DSC 8000. It features power-controlled design for direct and on the top. The cells are encapsulated by a polymer encapsulant accurate heat-flow measurements to and from the sample (Figure 1). The polymer encapsulant serves many functions – material. The cooling accessory is an Intracooler 2P mechanical it provides mechanical support, electrical isolation, and refrigerator. Nitrogen is used as the sample purge gas at protection against outdoor environmental elements of 20 mL/min. The instrument was calibrated with two metal moisture, UV radiation and temperature stress. Many different reference materials: indium and zinc were used for temperature materials can be used for encapsulation, but one commonly calibration, and indium was used for heat of fusion for used encapsulant for this purpose is EVA (ethylene-vinyl-acetate). heat-flow calibration. The EVA samples are from a solar PV manufacturer. They were cured at a high temperature and EVA, a thermal-set material, is a copolymer elastomer supplied pressure for some time. Each EVA sample weighed approxi- in sheet form for use in the encapsulation of PV modules. mately 10 mg. Each EVA sample cured at different times It has many desirable properties which make it the material was encapsulated in the standard aluminum pans. The DSC of choice for this application. program started from -50 ˚C and heated to 220 ˚C at 10 ˚C/min. • It is not adhesive at room temperature for easy handling. Results • It makes a permanent and adhesive tight seal in the The raw EVA material exhibits several transitions during solar-cell system through crosslinking and enhanced heating, as shown in Figure 2 (Page 3). It was heated in the bonding when the film is heated and pressed. DSC from -50 ˚C to 220 ˚C at 10 ˚C/min, and after that it • After crosslinking, the EVA has high optical transmittance, was cooled to the starting temperature quickly at 100 ˚C/min. good adhesion to the different module materials – it It was heated for the second time at the same heating rate. provides good dielectric properties and great moisture- The first heating curve shows an endothermic melting peak barrier properties with adequate mechanical compliance (26 J/g) followed by the exothermic curing peak with the to accommodate system thermal stresses due to the curing enthalphy of 16.6 J/g. The second heating curve different thermal-expansion coefficiencies. shows a glass transition (Tg) at -35.6 ˚C; the melting peak is smaller (12 J/g vs. 26 J/g) and there is no detectable curing During the PV-package process, the EVA sheet is placed exothermal peak. So by comparing the first heating curve between the solar cells and the backsheet/glass. It is heated, with the second heating curve, it is clear that the EVA raw pressed into place, and cured at a certain high temperature material is cured completely after first heating it up to 220 ˚C. for some time. Since the final cured material’s properties are largely dependent on the curing degree, it is important to For a partially cured EVA sample, the residual curing peak know the degree of curing of the EVA so that the encapsu- during the first heating will be between the curing enthalpy lation process is optimized. Differential scanning calorimetry of raw EVA material and zero for completely curing EVA. So (DSC) has been traditionally used for curing studies of thermoset the residual curing enthalpy can be used as an indicator of resins. DSC can study the degree of cure and curing kinetics. the curing degree of EVA material. A series of EVA samples In this note, different EVA materials with different curing with different curing time are studied by DSC and the results times were investigated with PerkinElmer‘s high-end DSC 8000. are shown in Figure 3 (Page 3). The calculated residual curing enthalpy is tabulated in Table 1 and fitted to a straight line in Figure 4 (Page 3). As can be seen, the residual curing enthalpy can be correlated to the curing time very nicely (R2 = 0.9893). Table 1. Residual curing enthalpy of eight different EVA samples with different curing times. EVA Curing Time ΔH (residual curing samples (min) enthalpy J/g) EVA-1 1 11.3572 EVA-2 2 10.7635 EVA-3 3 9.6878 EVA-4 4 7.9689 Figure 1. Scheme of a crystalline solar panel. EVA-5 5 7.5885 EVA-6 6 6.7448 EVA-7 8 4.9335 EVA-8 9 3.98112
  21. 21. Figure 2. The first (red) and second (blue) heating curve of raw EVA material.Figure 3. Partially cured EVA samples with different curing times. Conclusion This study shows that DSC can be used to study the curing degree of the EVA resin by measuring the residual curing enthalpy. The data show that the residual curing enthalpy can be correlated to the curing time in a linear way. The DSC test is quick and easy. The double-furnace PerkinElmer DSC 8000 delivers accurate heat-flow data with great reproducibility. The power-controlled design ensures great accuracy and true isothermal measure so that it can be used for both scanning-curing and isothermal-curing studies of EVA resin.Figure 4. The relationship between residual-curing enthalpy and the curingtime of the eight different EVA samples.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2010, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.009038_01
  22. 22. a p p l i c at i o n n o t e ICP-Mass Spectrometry Authors Jianmin Chen PerkinElmer, Inc. Shelton, CT 06484 USADetermination of Mercury is ubiquitous in nature, and the human health consequences of mercury exposure were recognized fromMercury in Wastewater prehistory to the present. The first emperor of unified China who came to power in 221 B.C., Qin Shi Huang, reportedlyby Inductively Coupled died of ingesting mercury pills that were intended to give him eternal life. The severity of mercurys toxic effectsPlasma-Mass Spectrometry depends on the form and concentration of mercury and the route of exposure. Although its potential for toxicity in highly contaminated areas such as Minamata Bay in Japan is well documented, research has shown that mercury can be a threat to the health of people and wildlife in many environments that are not obviously polluted. There is no safe level of mercury for humans. The main toxic effects of mercury are known to negatively affect the neurological, renal, cardiovascular and immunological systems.
  23. 23. Mercury exists in three chemical forms: elemental or metallic, organic or methylmercury, and inorganic complexes. Table 1. ELAN ICP-MS Instrumental Conditions and Experimental Parameters. Mercury has thousands of industrial applications. Some common uses for mercury include conducting electricity, RF power 1100 W measuring temperature and pressure, acting as a biocide, Plasma gas flow 15 L/min preservative, and disinfectant, as well as being a catalyst for Auxiliary gas flow 1.2 L/min reactions. Unlike most other pollutants, mercury is highly Nebulizer gas flow 0.96 L/min mobile, non-biodegradable, and bio-accumulative; as a result, it must be closely monitored to ensure its harmful Nebulizer MEINHARD® Concentric Type A3 effects on local populations are minimized.1 Thus, measurement Spray chamber Baffled Quartz Cyclonic of mercury in environmental samples, and in particular waste- Scanning mode Peak Hopping water, is of great importance as a major tool to protect Dwell time 50 ms the environment from mercury released through emissions Replicates 3 from manufacturing, use, or disposal activities. Currently, the prominent methods typically utilized by the environmental Integration time 1 sec/mass community for the determination of mercury generally require detection limits as low as 0.5 ng/L (ppt, parts- per-trillion).2 Sample Preparation The stability of mercury-containing solutions has been Traditionally, mercury is analyzed using Cold Vapor Atomic a topic of concern for all trace analysts performing Hg Absorption Spectroscopy (CVAAS) or Cold Vapor Atomic determinations. It is reported that a trace amount of gold Fluorescence Spectroscopy (CVAFS). Both of these techniques salt added to HNO3 preserved all forms of mercury. The are relatively straightforward to use and can accomplish gold ion acts as a strong oxidizing agent that converts or the analytical requirements of detection limits in the low maintains mercury as mercuric ion which remains in solution.3 ppt range. However, they are generally specific for mercury Thus, a solution of 2% (v/v) HNO3 containing 200 ug/L Au analysis only. was used for preparation of all samples and standards. In recent years, Inductively Coupled Plasma Mass Spectrometry Two simulated wastewater certified reference materials (ICP-MS) has become one of the most powerful analytical (Trace Metals Solutions, CWW-TM-A and CWW-TM-C, techniques for trace element analysis because of its high High-Purity Standards, Charleston, SC, USA) were prepared sensitivity, wide linear dynamic range, and simultaneous according the manufacturer’s description using the same multi-element detection capability. As a result, ICP-MS has diluent in this study. been increasingly adopted in environmental and biomonitoring laboratories for the simultaneous measurement of mercury Calibration with other toxic metals since this technique can offer the External calibration standards of mercury were at the level same analytical performance as CVAAS or CVAFS. This of 10, 20, 50, 100, 200, 500, 1000 ng/L. Figure 1 shows application note describes the application of ELAN® ICP-MS the calibration curve of 202Hg. The correlation coefficient is to the determination of mercury in wastewater. 0.999973, which allowed the accurate quantitative analysis of mercury at the low ppt levels. Instrumentation For this study, the PerkinElmer® ELAN DRC™ II ICP-MS was used for the analysis of wastewater samples under standard mode. The ELAN ICP-MS instrument conditions and general method parameters are shown in Table 1. Figure 1. External calibration curve of 202Hg. Standard solutions were prepared in 2% HNO3 containing 200 ug/L Au with concentrations ranging from 10 to 1000 ng/L.2
  24. 24. Spike recoveryThe spike recovery test was performed using two simulatedwastewater certified reference materials (HPS CWW-TM-Aand CWW-TM-C). The results are presented in Table 2. Table 2. Spike recovery test results from two simulated wastewater certified reference materials (HPS CWW-TM-A and CWW-TM-C). Wastewater Found Spike Measured Recovery Sample (ng/L) Level (ng/L) % (ng/L) CWW-TM-A 49 200 238 95 CWW-TM-C 375 1000 1370 99Memory effectIt is generally viewed that routine determination of mercuryby ICP-MS is affected by a pronounced memory effect in the Figure 2. Uptake and wash out profile for Hg at 1000 ng/L level. The signal ofsample introduction system. This results in long washout times four mercury isotopes returns to the background level in around 60 seconds,for the analyte, which affects the accuracy and reliability of which is equivalent to the typical rinse time used for many other analytes.the analytical procedure. To minimize the memory effect, thesystem was washed using 2% (v/v) HNO3 containing 200 ug/LAu between samples. Figure 2 shows the uptake and wash out Conclusionprofile of Hg. The signal of four mercury isotopes returns to The ELAN ICP-MS combines high sensitivities and superiorthe background level in around 60 seconds, which is equivalent detection limits with ease of use and high sample the typical rinse time used for many other analytes. Thus, This allows it to be an excellent tool for trace mercurythe results indicated application of gold salt is effective in determination in wastewater samples. Mercury can be detectedpreventing mercury sorption and vapor buildup within the simultaneously with the other trace elements of interest withinsample introduction system. a single sample run. References 1. J.O. Nriagu, Global inventory of natural and anthropogenic emissions of trace metals to the atmosphere, Nature 279 (1979) 409–411. 2. EPA Method 1631. Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry. 3. Mercury Preservation Techniques.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2009-2011, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.008973A_01
  25. 25. a p p l i c at i o n n o t e Thermogravimetric Analysis – GC Mass Spectrometry Author Greg Johnson PerkinElmer, Inc. Shelton, CT 06484 USAQualitative Analysis Introduction Thermogravimetric analysis (TGA)of Evolved Gases in measures the change in the weight of a sample as a function of temperature.Thermogravimetry by A limitation of TGA is that it cannot identifyGas Chromatography/ what material is lost at a specific tempera- ture. The analysis of gases evolved duringMass Spectrometry a TGA experiment by gas chromatography mass spectrometry (GC/MS) provides laboratories with a way to identify the compound or groups of compounds evolved during a specific weight-loss event in a TGA analysis. This application note discusses the utility of TG-GC/MS with an example application – the identification of specific organic acids evolved during TGA analysis of switchgrass.
  26. 26. Figure 3 describes in greater detail the pneumatic supply to the S-Swafer device and assists in explaining why this approach is so well suited to interfacing the Pyris 1 TGA to the Clarus 600 GC/MS. Figure 1. Clarus 600 GC/MS interfaced to the Pyris 1 TGA. Switchgrass (Panicum Irgatum) is a perennial warm-season grass native to the northern states of the USA; it is easily grown in difficult soils. Switchgrass is potentially useful in Figure 3. Schematic showing carrier-gas supply to the S-Swafer device. the production of biofuels, specifically cellulosic ethanol and bio-oil. The instrumentation used in this study was a PerkinElmer® The S-Swafer configuration is optimal because it will ensure Pyris™ 1 TGA interfaced to the PerkinElmer Clarus® 600 GC/ a very rapid adjustment of carrier gas to the Swafer device, MS with the S-Swafer™ micro-channel flow splitting device allowing for a rapid switch between backflush of the transfer (S4 configuration). The preferred mode of operation of the line and sampling from the TGA. The samples of evolved gas TGA maintains the atmosphere around the sample at ambi- are collected by setting a simple parameter in the GC method; ent atmospheric pressure. The sample is collected from the multiple samples can be collected during a TGA analysis. TGA by allowing the high vacuum of the MS to create a Additionally, backflush of the transfer line will isolate the pressure drop across the GC column, causing a flow of gas GC/MS and enable purge gas at the TGA to be switched from the TGA through the transfer line and the analytical from an inert gas (during analysis) to an air supply for column to the MS. During the analysis, there are times when cleaning of the TGA pan prior to the next sample. the TGA inlet will be surrounded by air, rather than an inert atmosphere. This would cause air to flow into the GC/MS; this Oven subambient cooling will be extremely useful in this is undesirable as it will cause oxidation to a number of dif- application, allowing protracted sampling periods to be ferent areas of the system. The S-Swafer device (shown in refocused into a narrow band of analytes on the column. Figure 2) is used to switch between backflushing of the TGA transfer line during non-sampling time and sampling Experimental of the TGA environment during analysis. The deactivated fused-silica transfer line used here was 1.6 m x 0.32 mm i.d. A few centimeters of the deactivated fused silica protrudes into the sample weighing area of the TGA. Approximately 30 cm of fused silica passes through the injector into the oven environment and is connected to the S-Swafer using specialized SilTite™ nuts and ferrules to ensure a leak-free connection that will not shrink and leak during normal or even extended thermal cycling of the main oven. In all cases, a 30 m x 0.32 mm analytical column was employed as this allows a carrier flow of approximately 1 mL/min with the fixed 1.00 atmosphere pressure drop from ambient at the TGA to vacuum at the MS. Data was Figure 2. Schematic showing the pneumatic interfacing of the TG-GC/MS acquired using an Elite™ WAX stationary phase. using the S-Swafer.2
  27. 27. A small quantity of dried and ground switchgrass was timed events that will be used to sample the evolved gasesplaced on the TGA pan and weighed using Pyris software. onto the GC/MS column. Note that the TGA is held iso-A rapid TGA analysis based on heating the sample from thermal for the first 5.0 min at which point heating begins.30 ˚C to 1000 ˚C at 100 ˚C/min in a nitrogen atmosphere Simultaneously, the GC/MS analysis is started.was performed to determine which regions of the weight-loss curve were to be further studied using the TG-GC/MS Figure 5 illustrates the TG-GC/MS analysis of the switch-technique. grass based on timed events that collect the evolved gases from the main transition shown in Figure 4. The smallerThe primary reason for using such rapid heating, which earlier transition, also seen in the same figure, was also sampledreduces the resolution of the weight-loss curve produced onto the GC/MS but preliminary findings indicate that thisby the TGA, is to transfer the evolved gas quickly into the is simply evolved water. The major transition produced largeGC column. A quick transfer will improve GC peak shape, numbers of oxygenated volatile organic compounds (VOCs),sensitivity and resolution. including some very polar species. Earlier work using a non- polar capillary column had generated extremely smeared-outAfter the sample was loaded onto the TGA and the furnace early-eluting peaks. The chromatogram below was generatedraised, the analysis was started immediately. The first step in using a thick-film polar Elite WAX column.the TGA heating program maintained the low initial furnacetemperature for 5 to 10 min. During this time, the furnaceenvironment is being purged with helium (or nitrogen/argon),and the carrier-gas pressure of 7.0 psig maintained at Aux 1(Figures 2 and 3) ensures that no sample can enter the ana-lytical column. After this initial hold period, the TGA furnacebegins to heat the sample, and simultaneously, the GC/MSrun is started using an external start command. Figure 5. TG-GC/MS analysis of the switchgrass sample on a 30 m x 0.32 mmBased on previous TGA runs on the same sample, timed x 1 μm Elite WAX within the GC method switch off the carrier gassupplied by the Aux 1 PPC module and then close thesolenoid valve (SV3) shown in Figure 2 (Page 2). This begins The three peaks labeled with asterisks in Figure 5 are identifiedthe sampling and this procedure is reversed to bring the sam- as a homologous series of free fatty acids (Figure 6 – Page 4),pling period to an end. After the sampling is complete, both based on a library search of their MS spectra (NIST® 2008).the GC oven-temperature program and MS data acquisition Usually in GC, a homologous series tends to elute in carbon-begins. The TGA can now be programmed to switch purge number order but here, the elution order appears to begases to clean the system using oxidation at elevated acetic, followed by formic, followed by propanonic acid. Astemperature, prior to the next analysis. this retention behavior is not typical and in the absence of a literature reference or a similar chromatogram in the publicA typical TGA weight-loss curve for the switchgrass is shown domain, it seemed prudent to analyze a simple retention-in Figure 4 and reveals a typical weight % loss curve for the time standard to confirm this tentative result. Figure 7 (Page 4)sample of switchgrass that was tested. In addition, super- shows the same analysis again but with the retention-timeimposed on the weight-loss curve is the derivative of this standard shown in parallel. This standard was a simplecurve which greatly assists the analyst in setting up the GC mixture diluted in water with a small (5 μL) aliquot of this aqueous solution deposited by syringe onto the TGA pan for analysis.Figure 4. Typical result for the TGA analysis of switchgrass. 3
  28. 28. Conclusions In this application note, we describe the technique of TG- GC/MS through the analysis of switchgrass. TG-GC/MS is demonstrated to be a valuable technique in the separation and identification of complex mixtures of gas evolved during a TGA analysis. The S-Swafer device is demonstrated as a means to interface a TGA to GC/MS. The main benefits are its simplicity and the inertness of the entire sample path.Figure 6. Mass spectra extracted from the total ion chromatogram of theswitchgrass sample. The spectral data matches that of acetic, formic andpropionic acid respectively available in the 2008 NIST® mass spectral library.Figure 7. TG-GC/MS analysis of the switchgrass sample (bottom) on a 30 mx 0.32 mm x 1 μm Elite WAX column and the analysis of a simple retentiontime mix (top) under the same TGA and GC conditions.PerkinElmer, Inc.940 Winter StreetWaltham, MA 02451 USAP: (800) 762-4000 or(+1) 203-925-4602www.perkinelmer.comFor a complete listing of our global offices, visit ©2010, PerkinElmer, Inc. All rights reserved. PerkinElmer® is a registered trademark of PerkinElmer, Inc. All other trademarks are the property of their respective owners.009030_01
  29. 29. a p p l i c at i o n n o t e ICP-Mass Spectrometry Authors Lee Davidowski, Ph.D. Zoe Grosser, Ph.D. Laura Thompson PerkinElmer, Inc. 710 Bridgeport Avenue Shelton, CT USAThe Determination Introduction Dietary supplements are regulated by the FDA under the general umbrella of foods,of Metals in Dietary but with different regulations than conventional foods. Dietary supplements have been defined by Congress as materials taken by mouth that include ingredients intended toSupplements provide dietary supplementation. They can be found in various forms, including tablets, powders, and liquids. They may consist of vitamins, minerals, herbs or other botanicals, amino acids, and substances such as enzymes, organ tissues, glandulars, and metabolites. Under the Dietary Supplement Health and Education Act of 1994 (DSHEA), the dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. FDA is responsible for taking action against any unsafe dietary supplement product after it reaches the market.1 One facet of ensuring a safe product is analysis of the final product before distribution. Although organic components often form the majority of a supplement, metals may be found due to their inclusion in vitamin structures such as vitamin B-12 (cobalt) and minerals, such as selenium. They may also be added as a contaminant through natural products or in the manu- facturing process. The measurement of toxic metals or metals intended to be present for quality and labeling confirmation may be required. Analysis challenges include measurement at low concentrations in a variety of matrices. In this note we will use inductively coupled plasma mass spectrometry (ICP-MS) to measure a variety of elements generally considered to be hazardous to human health at low to medium concentrations. The four elements generally considered to be hazardous and not necessary for nutrition are Pb, Cd, As, and Hg. The elements Se and Cr are often added at low concentrations for nutritional purposes and were also included.