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In the context of evaluating air sampling methods, laboratory experiments were performed to investigate the stability of eleven selected low boiling hydrocarbons (e.g. 1,3-butadiene, isoprene) adsorbed on four different carbon based adsorbents. The carbon molecular sieves Carboxen 569, Carboxen 1003, Carbosieve SIII and the graphitized carbon black Carbotrap X were tested. The influence of storage duration on the recovery of the analytes was examined by loading the adsorbent tubes with the test compounds via a sample loop under inert gas. Furthermore, the influence of sampling the hydrocarbons continuously from air on the recovery of the analytes was investigated using a simple experimental set-up providing a flow of synthetic air spiked with the hydrocarbons. Analysis of the loaded adsorbent tubes was performed by thermal desorption and capillary gas chromatography. Losses up to 80% of 1,3-butadiene and isoprene were observed for the carbon molecular sieves, occurring even immediately after the sampling step. In contrast, no significant losses of these reactive constituents were detected for Carbotrap X over a storage time of seven days. The laboratory investigations were confirmed in a field experiment.

For the comprehensive characterization of ambient air concentrations of a broad spectrum of volatile organic compounds (VOCs) an analytical method is described, consisting of adsorptive enrichment, thermal desorption without cryofocusing, and capillary gas chromatographic separation. The method was applied during two-week measuring campaigns in winter and summer 1995, and in the winter of 1996. Long-term sampling was carried out at sampling points in residential areas in the suburbs and near the city center of Leipzig. About 70 VOCs – mainly hydrocarbons from propene to hexadecane – were identified both by GC-MS and chromatographic retention data and quantified after external calibration. Mean values of VOC concentrations obtained during the sampling periods are reported and discussed with regard to the topographical location of the sampling points in the Leipzig area, seasonal variations, and possible emission sources.

Selectivity tuning is used in a system of series-coupled GC-columns of different polarity in order to improve the analysis of complex samples of essential oils. It is shown that selectivity tuning by changing the flow-rates in the single columns can be used for improving both the resolution and the reliability of identification. Furthermore, by combining this method with column switching techniques (multidimensional GC) a reduction of sample complexity could be reached. Isothermal retention indices of 35 terpenoid compounds were ascertained using a non-polar and a polar capillary column serving as the input-values of a computer program which enables the prediction of system retention times at any adjusted flow-rate. Therefore, promising chromatographic conditions for the separation of interesting compounds could be selected without great experimental effort and some of these compounds could be identified with a high degree of reliability.