Long-term measurement of volatile organic compounds in ambient air by canister-based one-week sampling method

摘要

A canister-based 1 week sampling method using a mechanical flow controller and a 6 L fused-silica-lined canister was evaluated for the long-term measurement of 47 VOCs in ambient air at pptv (volume/volume) to ppv levels by use of a three-stage preconcentration method followed by GC-MS analysis.The GC conditions were initially optimized for complete separations of several pptv-level VOCs (e.g.vinyl chloride,1,3-butadiene,acrylonitrile,1,2-dichloroethane and chrloroform)in ambient air because the selected ions are easily interfered with by coexisting C_4-,C_5-hydrocarbons and analytes presented at ppbv levels.Thirty-four VOCs determined by the 1 week and 24h sampling method in December 16-22 (2002) had cocentractions of 6.0-15 000 pptv per compound.Concentrations of 28 VOCs (including polar VOCs (e.g.methyl isobutyl ketone and butyl acetate)) obtained by the method were approximately equal to the mean values calcualted from 24h sampling (<+-10% deviation).Six VOCs that had low concentrations of 6.0-43 pptv showed more than +-10% deviation.Thirteen VOCs were not detected during the entire sampling period.The effect of the relatively humidity or ozone for the specific VOCs (e.g.MIBK,butyl acetate,vinyl chloride,1,3-butadiene and styrene) was negligible.