ONLINE MONITORING OF FLOWING SAMPLES USING SOLID-PHASE MICROEXTRACTION GAS-CHROMATOGRAPHY

The rapid sampling and concentration response of solid phase microextraction (SPME) facilitate the monitoring of organic analytes present in a flowing stream. It was determined that in addition to convection introduced by flow in the system, an efficient means of agitation is required to achieve rapid extractions. Three agitation techniques; magnetic mixing, intrusive mixing and sonication were tested. While magnetic stirring is inexpensive and easy to automate, it exhibited low mixing efficiency. Intrusive mixing allows efficient agitation but caused sample heating and is not easily amenable to on-line analysis. Sonication proved to be the most efficient and the most convenient means of agitation for sampling from flowing streams. For example, toluene equilibrates in less then 1 min, which is very dose to theoretical predictions assuming perfect agitation conditions. The on-line SPME-GC technique allows gas chromatography to be incorporated into a flow-injection analysis system.