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

The rapid sampling and concentration response of solid phase microextr action (SPME) facilitate the monitoring of organic analytes present in a flowing stream. It was determined that in addition to convection in troduced by flow in the system, an efficient means of agitation is req uired to achieve rapid extractions. Three agitation techniques; magnet ic 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 sa mple heating and is not easily amenable to on-line analysis. Sonicatio n proved to be the most efficient and the most convenient means of agi tation for sampling from flowing streams. For example, toluene equilib rates in less then 1 min, which is very dose to theoretical prediction s assuming perfect agitation conditions. The on-line SPME-GC technique allows gas chromatography to be incorporated into a flow-injection an alysis system.