Air Most methods are based on that of Hill et al. (1976a), using adsorption on activated charcoal, desorption with carbon disulfide and analysis by GC/FID. Kruschel et al. (1994) used a three-stage carbon molecular sieve adsorbent cartridge to collect a wide range of selected polar and non-polar VOCs. After purging with helium prior to analysis, levels of water and other interfering compounds were reduced sufficiently to allow cryogenic preconcentration and focusing of the sample onto the head of the analytical column. VC was detected at levels below the detection limit of former methods. Landfill gas monitoring has been carried out by trapping VC on a molecular sieve, and samples have been analysed using, for instance, GC/MS (Bruckmann & Mülder, 1982) or GC/ECD with prior conversion to the 1,2-dibromo derivative (Wittsiepe et al., 1996).