A comparison of sampling and analysis methods for low­ppbC levels of volatile organic compounds in ambient air

Abstract

A carefully designed study was conducted during the summer of 1998 to collect samples of ambient air by canisters and compare the analysis results to direct sorbent preconcentration results taken at the time of sample collection. Thirty-two 1 h sample sets were taken, each composed of a "near-real-time" sample analyzed by an autoGC-MS XonTech 930/Varian Saturn 2000 system, and Summa and Silco canisters. Hourly total non-methane organic carbon (TNMOC), ozone, and meteorological measurements were also made. Each canister was analyzed on the autoGC-MS system for a target list of 108 volatile organic compounds (VOCs) and on a manual cryosampling GC-FID system. Comparisons were made between the collection and analysis methods. Because of the low sample loading (150-250 ppbC TNMOC), these comparisons were a stringent test of sample collection and analysis capabilities. The following specific conclusions may be drawn from this study. Reasonable precision (within 15% mean difference of duplicate analyses from the same canister) can be obtained for analyses of target VOCs at low-ppbC concentrations. Relative accuracy between the GC-MS and GC-FID analysis methods is excellent, as demonstrated by comparisons of analyses of the same canisters, if measurements are sufficiently above the detection limits. This is especially significant as the GC-MS and GC-FID were independently calibrated. While statistically significant differences may be observed between the results from canister and near-real-time samples, the differences were generally small and there were clear correlations between the canister results and the near-real-time results. Canister cleanliness limits detection below the EPA Method TO-14 acceptance standard of 0.2 ppbv (0.2-2 ppbC for target analytes).

Validation of an Evacuated Canister Method for Measuring Part-Per-Billion Levels of Chemical Warfare Agent Simulants

“…The canisters were analyzed 1-7 days after collection with the same concentrator/GC-MS system. 11 They found only slight differences between the near-realtime and canister samples with clear correlations between the two types of samples. Many of the dependent samples had t-test comparisons that were significant.…”

“…Daughtrey et al 11 used two alternative methods to sample CCl 4 , ␣-pinene, isoprene, benzene, n-decane, toluene, m-,p-xylene, and n-octanal in outdoor air. The first method was a near-real-time measurement using a twotrap organic vapor concentrator attached to a gas chromatograph/mass spectrometer.…”

Breath Analysis for Medical Diagnosis

“…Currently this method of determination is the primary procedure utilised to identify VOC's in human breath. Comparative studies have shown however that there is little difference in accuracy of determination even with low concentration (ppbv) organics compared with other detection techniques (15). The study involved the detection of 108 organics in human breath, using both real time and canister analysis.…”

Efeitos da poluição atmosférica na área do Aeroporto Internacional de São Paulo - Guarulhos sobre ensaio de bioindicadores vegetais

“…Após a análise qualiquantitativa, o espectro resultante pode ser trabalhado para se chegar a um resultado quantitativo. (Tolnai et al, 2000;Doskey & Bialk, 2001;Colon et al, 2001;Ballestra et al, 2001;Mohamed et al, 2002;Ho et al, 2002a;Ho et al,2002b;Daughtrey et al, 2001;Na et al, 2003;Barletta et al, 2002).…”