SORBENTS IN SAMPLING - STABILITY AND BREAKTHROUGH MEASUREMENTS

The stability of several sorbents charged with chlorinated and non-chlorinated hydrocarbons has been studied over a period of months and years. Especially Tenax showed good results whereas some others were found to be unsuitable for storage over a prolonged time. Charging of the sorbent tubes sometimes resulted in reproducibility problems due to minor breakthrough as a result of the presence of other analytes during charging (or sampling). This phenomenon was studied using a membrane inlet mass spectrometer. With this instrument the breakthrough curves of components, as pure compounds or in a mixture, can be monitored continuously. The results of these experiments indicate that breakthrough is not a function of concentration of the analyte, but in mixtures may depend strongly on the composition of the mixture.