SIMPLE LABORATORY-MADE SYSTEM FOR THE DETERMINATION OF C-2-C-7 HYDROCARBONS RELEVANT TO PHOTOCHEMICAL SMOG POLLUTION

A simple gas chromatographic system suitable for determining volatile organic compounds from C-2 to C-7 in air is described. It consists of a capillary cold trap filled with graphitic carbon, a thermodesorbing device, a capillary gas chromatograph equipped with an alumina column and a flame ionization detector. Dry, as well as humid, air samples ca n be analysed with our system. Up to 2-1 samples of air can be enriche d on our trapping device by using Nafion membranes for removing water. Direct analysis of air samples is possible by enriching 250 mi on the carbon trap. The recovery, sensitivity and linearity of our system ha ve been checked with standard mixtures and real samples. The performan ces have been compared with those afforded by a commercially available instrument exploiting a different enrichment procedure. The results o btained show that our analyser can be successfully applied to determin ations of C, to C, hydrocarbons present in air samples at levels of 0. 01 ppb (v/v). (C) 1997 Elsevier Science B.V.