A cryogenic trap/porous polymer sampling technique for the quantitative determination of ambient volatile organic compound concentrations

Abstract

A technique is described for concentrating atmospheric volatile organic compounds (VOCs) to permit their quantitative determination. The technique relies on cryogenic trapping followed by volatilization of the sample components and subsequent transfer to a Tenax tube cartridge assembly. This technique was evaluated using standard samples and by sampling and analysis for selected hydrocarbons (chloroethane, chlorobenzene, tetrachloroethylene, benzene and toluene) in Philadelphia, PA, and San Jose, CA. The results are compared with those obtained using a cryogenic concentration technique with on-site chromatographic analysis. On the average, these two techniques agreed to ± 40%, for benzene, toluene and tetrachloroethylene concentrations ranging from ~ 1–30 ppb (for similar sampling times). The technique for this data set is shown to have a detection limit of ~ 10–20 ppt (using GC/MS analysis), an estimated accuracy and precision of ± 20% and 15%, respectively, and is shown to circumvent many of the disadvantages associated with using cryogenic or porous polymer concentration techniques alone. The technique should be applicable to determinations of VOCs having a wide range of volatilities.