Determination of a wide range of volatile organic compounds in ambient airusing multisorbent adsorption/thermal desorption and gas chromatography mass spectrometry

Adsorption/thermal desorption with multisorbent air-sampling cartridges was developed for the determination of 87 method analytes including halogenate d alkanes, halogenated alkenes, ethers, alcohols, nitriles, esters, ketones , aromatics, a disulfide, and a furan, The volatilities of the compounds ra nged from that of dichlorofluoromethane (CFC12) to that of 1,2,3-trichlorob enzene. The eight most volatile compounds were determined using a 1,5-L air sample and a sample cartridge containing 50 mg of Carbotrap B and 280 mg o f Carboxen 1000; the remaining 79 compounds were determined using a 5-L air sample and a cartridge containing 180 mg of Carbotrap B and 70 mg of Carbo xen 1000, Analysis and detection were by gas chromatography/mass spectromet ry, The minimum detectable level (MDL) concentration values ranged from 0.0 1 parts per billion by volume (ppbv) for chlorobenzene to 0.4 ppbv for brom omethane; most of the MDL values were in the range 0.02-0.06 ppbv, No break through was detected with the prescribed sample volumes. Analyte stability on the cartridges was very good. Excellent recoveries were obtained with in dependent check standards. Travel spike recoveries ranged from 90 to 110% f or 72 of the 87 compounds. The recoveries were less than 70% for bromometha ne and chloroethene and for a few compounds such as methyl acetate that are subject to losses by hydrolysis; the lowest travel spike recovery was obta ined for bromomethane (62%), Blank values for all compounds were either bel ow detection or very low. Ambient atmospheric sampling was conducted in New Jersey from April to December, 1997, Three sites characterized by low, mod erate, and high densities of urbanization/traffic were sampled. The median detected concentrations of the compounds were either similar at all three s ites (as with the chlorofluorocarbon compounds) or increased with the densi ty of urbanization/traffic (as with dichloromethane, MTBE, benzene, and tol uene), For toluene, the median detected concentrations were 0.23, 0.42, and 0.70 ppbv at the three sites. Analytical precision was measured using dupl icate sampling. As expected, the precision deteriorated with decreasing con centration, At concentrations greater than 0.2 ppbv, most duplicates differ ed by less than 20%; below the MDL values, the differences between the dupl icates were larger, but they were still typically less than 40%.