CONTINUOUS GAS-CHROMATOGRAPHIC MONITORING OF LOW CONCENTRATION SAMPLE STREAMS USING AN ONLINE MICROTRAP

An on-line microtrap was made by packing a few centimeter long narrow bore capillary tubing with an adsorbent. The sample stream containing the analytes is introduced into the GC column through the microtrap. The analytes are trapped in the microtrap as they flow through it, and can be desorbed by heating the microtrap using a pulse of electric current. The heating is done very rapidly, so that the ''desorption pulse'' is sharp enough to be an injection for the GC separation. Thus, the microtrap serves as a sample pre-concentrator as well as an injector. Continuous monitoring is done by making these injections at fixed intervals of time (every few seconds to every few minutes) and for each injection a chromatogram is obtained. In this investigation, microtrap characteristics have been studied and particular attention has been given to its sample trapping characteristics.