Analysis of volatile organic compounds in air using retention indices together with a simple thermal desorption and cold trap method

A simple, low-cost thermal desorption and cold trap device was constructed and tested with a two-channel gas chromatograph equipped with SE-54 fused-silica capillary columns or a Al2O3/KCl column and flame ionization, nitrogen-phosphorus or electron-capture detectors. Good repeatability was obtained in the identification of ten aromatic compounds, with use of n-alkanes as index compounds for the determination of retention indices. The performance of the equipment and method with real samples was evaluated for the determination of volatile halogenated compounds and small alcohols in urban air, and for the determination of N,N-dimethylformamide (DMF) in air nearby a chemical plant. A collection method was developed for highly volatile halogenated hydrocarbons and small polar alcohols. At ambient temperature they were not easily trapped completely and humidity was a problem. Drying tubes were needed in front of the sampling tubes, which were placed inside copper tubes refrigerated in a cold box. Compounds were reliably identified, and some of the halogenated compounds and DMF were determined quantitatively. (C) 1997 Elsevier Science B.V.