Automated Methanol Extraction of High-Level Soil Samples Using the Teledyne Tekmar Atomx XYZ and Agilent 7890B GC/5977A MSD
US EPA Method 5035 was used to determine the concentration of volatile organic compounds (VOCs) in high-level soil samples using purge and trap concentration. For this study, a Teledyne Tekmar Atomx XYZ purge and trap (P&T) system and Agilent 7890B Gas Chromatograph (GC)/5977A Mass Spectrometer (MS) was used to generate a working linear calibration curve, method detection limits (MDLs), recovery and carryover data for high-level soil samples. Additionally, the study will demonstrate the Atomx XYZ’s ability to automate the methanol extraction process, as well as the system’s ability to reduce carryover. It should also be noted, that US EPA 5035 includes the handling of soils which exceed normal VOC concentration levels (greater than 200 ppb).1
US EPA Method 5035 allows for two soil sample collection options that can be used in accordance with US EPA Method 8260C: “The first option is to collect an appropriate sample volume in a pre-weighed vial with a septum-sealed screw-cap that contains a water-miscible organic solvent (e.g., methanol). At the time of analysis, an aliquot of the solvent is removed from the vial and diluted into water along with the internal standards and surrogates, then purged using Method 5030 and analyzed by an appropriate determinative method. The second option is to collect a bulk sample in a VOA vial without the use of a chemical preservative. A portion of that sample is removed from the container in the laboratory and is dispersed in a water-miscible solvent to dissolve the volatile organic constituents. An aliquot of the solution is added to reagent water in a purge tube. Surrogates and internal standards (if applicable) are added to the solution, then purged using Method 5030, and analyzed by an appropriate determinative method.” 1,2
For this study, 5 and 7 gram (g) baked sand samples were placed in 40 mL VOA vials with methanol, spiked with standard, a stir bar added and then sealed. The methanol extraction process was then conducted by the 84-position Atomx XYZ automated system including: addition of methanol via the system’s 3-stage needle, mixing of the sample to release VOCs from the sample into the methanol, extraction of a methanol aliquot, and the addition of 5 mL of DI water to that aliquot for sparging. The remaining analysis used normal P&T conditions.
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