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Sample Integrity Evaluation and EPA Method 325b Interlaboratory Comparison for Select Volatile Organic Compounds Collected Diffusively on Carbopack X Sorbent Tubes
Oliver, K., T. Cousett, D. Whitaker, L. Smith, S. Mukerjee, C. Stallings, E. Thoma, L. Alston, M. Colon, T. Wu, AND S. Henkle. Sample Integrity Evaluation and EPA Method 325b Interlaboratory Comparison for Select Volatile Organic Compounds Collected Diffusively on Carbopack X Sorbent Tubes. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 163:99-106, (2017).
The U.S. Environmental Protection Agency (EPA) recognized the need to refine regional emission inventories since revised emission control requirements were being established in EPA’s New Source Performance Standards for the oil and natural gas sector (78 Federal Register 58416 (September 23, 2013)). To meet this need, EPA Methods 325A/B have been established to monitor fence line benzene levels that may originate from fugitive and area sources within petroleum refineries (U.S. Environmental Protection Agency, 2015a; 2015b). The implementation of Method 325 most commonly employs passive tube samplers using Carbopack X or alternative sorbents for collection and subsequent determination of benzene using thermal desorption/gas chromatography mass spectrometry (TD/GC-MS) analytical techniques.
Sample integrity evaluations and inter-laboratory comparisons were conducted in application of U.S. Environmental Protection Agency (EPA) Methods 325A/B for monitoring benzene and additional selected volatile organic compounds (VOCs) usingpassive-diffusive Carbopack X tube samplers. Samples were refrigerated for up to 240 days and analyzed using thermal desorption/gas chromatography-mass spectrometry techniques at the EPA ORD Laboratory in Research Triangle Park, NC, to evaluate sample integrity. For the interlaboratory comparisons, three commercial analytical laboratories were asked to follow Method 325B when analyzing samples of VOCs that were collected in field and laboratory settings for EPA studies. Overall results indicate that the selected VOCs generally were stable for 6 months or longer when samples were refrigerated. This suggests the specified maximum 30-day storage time of VOCs collected diffusively on Carbopack X passive samplers using Method 325B may be able to be relaxed. Interlaboratory comparison results were in agreement for the challenge samples loaded diffusively in an exposure chamber in the laboratory, with most measurements being within ± 25% of the theoretical concentration. Statistically significant differences among laboratories for ambient challenge samples were small, <1 part per billion by volume (ppbv). All laboratories exhibited good precision and were generally in agreement with each other.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
EXPOSURE METHODS & MEASUREMENT DIVISION