Optimal VOC Method Parameters for the StratUm PTC Purge & Trap Concentrator

Size: px

Start display at page:

Download "Optimal VOC Method Parameters for the StratUm PTC Purge & Trap Concentrator"

Juliana Chandler
5 years ago
Views:

Optimal VOC Method Parameters for the StratUm PTC Purge & Trap Concentrator Application Note Introduction Environmental laboratories have utilized the Purge & Trap sample concentration technique for

1 Optimal VOC Method Parameters for the StratUm PTC Purge & Trap Concentrator Application Note Introduction Environmental laboratories have utilized the Purge & Trap sample concentration technique for over 30 years. This classical technique offers many benefits in regards to increasing sample throughput without sacrificing final detection sensitivity. The StratUm PTC offers a fresh new approach to Purge & Trap that now offers unprecedented precision, accuracy, and system cleanliness. The increased precision and accuracy are achieved by the utilization of an ultra-fast trap heater. By desorbing the compounds of interest off the analytical trap quickly and efficiently, the StratUm PTC will assist in achieving superior chromatography, which in turn results in better reportable data. The system cleanliness is enhanced by the StratUm PTC s new sample flow path. The new flow path has made great strides to ensure heating consistency throughout the entire sample pathway, thus minimizing any potential coldspots, which may trap or slow down certain compounds. Another innovation, which helped enhance system cleanliness, is the superior inert tube coating utilized by the StratUm PTC. Background contamination is dramatically reduced to give you better analytical performance. This application note will discuss optimal method parameters for achieving a calibration curve of 0.5 to 200ppb for 102 Volatile Organic Compounds (VOCs). The target compounds are found in the US Environmental Protection Agency (USEPA) 8260B list. Experimental Five standard mixes were used to make up the reported compound list. They were purchased from Restek ( See Table 1 for details. The calibration was built with concentrations of 0.5, 5.0, 25, 100, and 200ppb. An Agilent 6890GC and 5973MS were used for separation and detection. The purge and trap concentrator utilized was the Teledyne Tekmar StratUm PTC. The autosampler used was the Teledyne Tekmar SolaTek 72 Multi Matrix Sampler. The SolaTek 72 added the internal standards automatically during the sample transfer. The sample purging was performed in the StratUm PTC. The adsorbant trap utilized was the Vocarb Strat-Trap. Optimal method parameters can be found in Tables 2 and 3.

2 Table 1. Reported Compound Mix Standard Mix Cat # or Specific Compounds 8260B MegaMix Calibration Mix Cat # Calibration Mix #1 (gases) Cat # VOA Calibration Mix #1 (ketones) Cat # B Acetate Mix (revised) Cat # California Oxygenates Mix Cat # Internal Standards Surrogates Pentaflourobenzene, 1,4 Diflourobenzene, Chlorobenzene d5 Dibromoflouromethane, Toluene d8, BFB Table 2. StratUm PTC Parameters (utilizing a Vocarb Strat Trap) Variable Value Variable Value Valve Oven Temp 140 Deg C Dry Purge Flow 100 ml/min Transfer Line Temp 140 Deg C Dry Purge Temp. 20 Deg C Sample Mount Temp 90 Deg C Desorb Preheat 250 Deg C Purge Ready Temp 35 Deg C Desorb Temp. 250 Deg C Condenser Ready Temp 40 Deg C Desorb Time 2.00 min Condenser Purge Temp 20 Deg C Desorb Flow 400 ml/min Purge Time 11 min Trap Bake Temp 290 Deg C Purge Flow 40 ml/min Trap Bake Time 5.0 min GC Start Start of Desorb Trap Bake Flow 400 ml/min Dry Purge Time 1.00 min Condenser Bake Temp 225 Deg C Table 3. GC/MS Parameters Variable GC Column / Gas RTX VMS Value 20m x 0.18mm, 1.00 micrometer film; He at 1.0 ml/min GC Injector GC Oven Mass Spec Split ratio: 80:1, Temp 150 deg C Int. temp 35 deg C, hold 2.00 min; Ramp rate of deg/min to 85 deg C, hold for 0.00 min.; Ramp rate of deg/min to 210, hold for 3.00 min.; (Total run time of min) Interface at 250 C, MS quad 150 C; MS source at 230 C, low mass 35 amu

3 Calibration Curve Data Compound Ave. RF %RSD Compound Ave. RF %RSD Pentafluorobenzene (IS) ISTD 2 Cleve Dichlorodifluoromethane ,2,3 Trichloropropane Chloromethane cis 1,3 Dichloropropene Vinyl Chloride Toluene d8 (surr) Bromomethane Toluene Chloroethane (Ethyl Chloride) Nitropropane Trichlorofluoromethane Tetrachloroethene Diethyl Ether Methyl 2 Pentanone Carbon Disulfide trans 1,3 Dichloropropene ,1,2 Trichlorofluoroethane (Freon ) ,1,2 Trichloroethane Iodomethane Ethyl Methacrylate Allyl Chloride Dibromochloromethane Methylene Chloride ,3 Dichloropropane Acetone ,2 Dibromoethane trans 1,2 Dichloroethene n Butyl Acetate Diisopropyl Ether Hexanone Ethyl Acetate Chlorobenzene d5 (IS) ISTD Chloroprene Chlorobenzene cis 1,2 Dichloroethene Ethylbenzene ,1 Dichloroethane ,1,1,2 Tetrachloroethane Methyl Acetate M&P Xylene Methyl tert Butyl Ether(MTBE) Ortho Xylene tert Butyl Alcohol (TBA) Styrene Acetonitrile Bromoform Acrylonitrile Isopropylbenzene Propionitrile Tetrahydrofuran (THF) Ethyl tert Butyl Ether (ETBA) n Amyl Acetate ,1 Dichloroethene BFB (surr) ,2 Dichloropropane n Propylbenzene Bromochloromethane trans 1,4 Dichloro 2 Butene Chloroform Nitrobenzene Carbon Tetrachloride Bromobenzene Methyl Acrylate ,1,2,2 Tetrachloroethane ,1,1 Trichloroethane ,3,5 Trimethylbenzene Dibromofluoromethane (surr) Chlorotoluene ,1 Dichloropropene cis 1,4 Dichloro 2 Butene Butanone (MEK) Chlorotoluene Benzene Tertbutylbenzene Methacrylonitrile Pentachloroethane tert Amyl Methyl Ether (TAME) ,2,4 Trimethylbenzene ,2 Dichloroethane sec Butylbenzene Isobutyl Alcohol p Isopropyltoluene Isopropyl Acetate ,3 Dichlorobenzene Trichloroethene ,4 Dichlorobenzene ,4 Difluorobenzene (IS) ISTD n Butylbenzene Dibromomethane ,2 Dichlorobenzen ,2 Dichloropropane ,2 Dibromo 3 Chloropropane Bromodichloromethane Hexachlorobutadiene Methyl Methacrylate ,2,4 Trichlorobenzene Chloroethanol Naphthalene n Propyl Acetate ,2,3 Trichlorobenzene

4 Sample Results from 30 Consecutive Runs: In order to demonstrate the repeatability of the StratUm PTC, the 50ppb calibration mixture was analyzed 30 consecutive times to demonstrate repeatability and accuracy. The entire analysis time for 30 runs was approximately 15 hours. This demonstrates calibration curve robustness, system reliability, and performance. Although all of the compounds in the list were analyzed, this paper reports four compounds representing different molecular weight ranges. Sample Name Ave (ppb) Std Dev (ppb) RSD (%) Vinyl Chloride Iodomethane Cleve Naphthalene Vinyl Chloride 50ppb Repeatability a n a l y si s r e p l i c a t e Iodomethane 50ppb Repeatability analysis r eplicat e

5 2 Cleve 50ppb Repeatability a na l y si s r e pl i c a t e Naphthalene 50ppb Repeatability a na l y si s r e p li c a t e MDL Calculation The minimum detection limit was determined by running seven replicates of the 0.5ppb calibration curve standard. The appropriate factor was applied and the MDLs calculated are presented in the following table. Compound run 1 run 2 run 3 run 4 run 5 run 6 run 7 Ave std dev MDL Dichlorodifluoromethane Chloromethane Vinyl Chloride Bromomethane Chloroethane Trichlorofluoromethane Carbon Disulfide Iodomethane Methylene Chloride Trans 1,2 dichloroethene ,1 Dichloroethane Propiontrile ,1 Dichloroethene ,2 Dichloropropane Bromochloromethane Chloroform Carbon Tetrachloride ,1,1 Trichloroethane

6 Compound run 1 run 2 run 3 run 4 run 5 run 6 run 7 Ave std dev MDL Dibromofluoromethane (surr) ,1 dichloropropene Benzene ,2 Dichloroethane Trichloroethane Dibromomethane ,2 Dichloropropane Bromodichloromethane Cleve Cis 1,3 Dichloropropene Toluene d8 (surr) Toluene Tetrachloroethene Trans 1,3 Dichloropropene ,1,2 Trichloroethane Dibromochloromethane ,3 Dichloropropane ,2 Dibromoethane Chlorobenzene Ethylbenzene ,1,1,2 Tetrachloroethane M&P Xylene O Xylene Styrene Bromoform Isopropylbenzene BFB (surr) N propylbenzene Bromobenze ,1,2,2 Tetrachloroethane ,3,5 Trimethylbenzene Chlorotoluene Trans 1,4 Dichloro 2 Butene Chlorotoluene Tertbutylbenzene ,2,4 Trimethylbenzene Sec Butylbenzene P Isopropyltoluene ,3 Dichlorobenzene ,4 Dichlorobenzene N Butylbenzene ,2 Dichlorobenzene ,2 Dibromo 3 Chloropropane Hexachlorobutadiene ,2,4 Trichlorobenzene Naphthalene ,2,3 Trichlorobenzene

7 System Cleanliness A purge and trap system needs to ensure system cleanliness so that there are no false positive hits immediately after a high concentration sample has been run. A false positive can be the result of a memory effect within the systems flow path or trapping material. The memory effect can most commonly be attributed to one of two issues, activation sites or cold spots. The method parameters called out in this application note will help to ensure that the system will run at optimal performance. The following data represents the running of a 200ppb standard mix and the subsequent 5 blanks. Clearly seen, the carryover effect is minimized by the StratUm s sample path integrity. By showing all compounds going to <0.01% relative detection, this shows the overall cleanliness of the system in regards to component contamination. Compound 200 ppb Std. %Carryover %Carryover %Carryover %Carryover %Carryover Dichlorodifluoromethane Chloromethane Vinyl Chloride Bromomethane Chloroethane Trichlorofluoromethane Carbon Disulfide Iodomethane Methylene Chloride Trans 1,2 dichloroethene ,1 Dichloroethane Propiontrile ,1 Dichloroethene ,2 Dichloropropane Bromochloromethane Chloroform Carbon Tetrachloride ,1,1 Trichloroethane Dibromofluoromethane (surr) ,1 dichloropropene Benzene ,2 Dichloroethane Trichloroethane Dibromomethane ,2 Dichloropropane Bromodichloromethane Cleve Cis 1,3 Dichloropropene Toluene d8 (surr) Toluene Tetrachloroethene Trans 1,3 Dichloropropene ,1,2 Trichloroethane Dibromochloromethane ,3 Dichloropropane ,2 Dibromoethane Chlorobenzene Ethylbenzene ,1,1,2 Tetrachloroethane M&P Xylene O Xylene Styrene Bromoform Isopropylbenzene BFB (surr) N propylbenzene Bromobenze ,1,2,2 Tetrachloroethane ,3,5 Trimethylbenzene Chlorotoluene Trans 1,4 Dichloro 2 Butene Chlorotoluene Tertbutylbenzene ,2,4 Trimethylbenzene Sec Butylbenzene P Isopropyltoluene ,3 Dichlorobenzene ,4 Dichlorobenzene N Butylbenzene ,2 Dichlorobenzene

8 Compound 200 ppb Std. %Carryover %Carryover %Carryover %Carryover %Carryover 1,2 Dibromo 3 Chloropropane Hexachlorobutadiene ,2,4 Trichlorobenzene Naphthalene ,2,3 Trichlorobenzene Conclusion The StratUm PTC has demonstrated clear advancements in regard to system performance, repeatability, and cleanliness. These successes are attributed to four key elements. First, excellent purge efficiency by employing a digital mass flow controller to ensure accurate gas handling. Second, ultra-low carryover as a result of the Siltek inert pathway. Third, superior water management being achieved by Tekmar s innovative U condensate trap significantly minimizing the amount of water entering the GC and detector. And forth, the exclusive trapping technique using a rapid nichrome trap heater offers unprecedented gas resolution. All four of these attributes contribute to superior analytical performance of the StratUm PTC.

Analysis of Volatile Organic Compounds in Soil Samples by EPA Method 8260 with The Stratum PTC and SOLATek 72 Multi-Matrix Autosampler

Analysis of Volatile Organic Compounds in Soil Samples by EPA Method 8260 with The Stratum PTC and SOLATek 72 Multi-Matrix Autosampler Application Note By: Teri Dattilio Introduction Purge and Trap concentration