SORBENTS IN SAMPLING - STABILITY AND BREAKTHROUGH MEASUREMENTS

The stability of several sorbents charged with chlorinated and non-chl orinated hydrocarbons has been studied over a period of months and yea rs. Especially Tenax showed good results whereas some others were foun d to be unsuitable for storage over a prolonged time. Charging of the sorbent tubes sometimes resulted in reproducibility problems due to mi nor breakthrough as a result of the presence of other analytes during charging (or sampling). This phenomenon was studied using a membrane i nlet mass spectrometer. With this instrument the breakthrough curves o f components, as pure compounds or in a mixture, can be monitored cont inuously. 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.