Stability of Trace-Level Volatile Organic Compounds Stored in Canisters and Tedlar bags

Fifty-six volatile organic compounds (VOCs), known to be ozone precursors, were stored in three media (SUMMA and Silocan canisters and Tedlar bags) to evaluate their stability in these storage media. An analysis of samples of air followed the procedures described in the US EPA Method TO-15, and was performed using gas chromatograph (GC) equipped with a mass spectrometer (MS). The first-order decay model matched 87 % of the observations. These 56 VOCs were classified into four groups-alkanes, alkenes, aromatics and biogenics. Alkenes and biogenics exhibited lower recovery rates than those of alkanes and aromatics. After a seven-day (7-d) storage period, 87 % of alkenes could be recovered from canister storage and 82 % were recovered from Tedlar bag storage. Isoprene, a major component in biogenic VOCs, exhibited a recovery rate of only 75±8 % after storage for seven days in canisters and Tedlar bags. Storage conditions (humidity and temperature) affected the degradation constant of each VOC. The calculated average half-lifes of 56 VOCs for SUMMA canisters, Silcocan canisters, and Tedlar bags were 45±6, 52±6, and 37±4 days, respectively. The VOCs stored in Tedlar bags had a lower recovery than those stored in canisters.