KINETIC-MODEL OF MEMBRANE EXTRACTION WITH A SORBENT INTERFACE

Membrane extraction with a sorbent interface (MESI) is an unique sampl e preparation alternative for trace organic analysis, The main feature s of MESI include its solvent-free nature, ?he rugged and simple desig n with no moving parts for long-term reliable performance, the fact th at it is a single-step process which ensures good precision, its easy automation, and its feasibility for on-site operation, Among the avail able membrane extraction modules designed for the MESI system, the hea dspace configuration has continued to show its superior durability and versatility in membrane applications, The headspace membrane extracti on configuration effectively eliminates the need for a sampling pump a nd flow metering and hence prevents the extraction system from pluggin g and greatly simplifies the extraction process, The module can be use d for extraction of VOCs from gaseous, aqueous, or solid samples, A ma thematical model has been developed for headspace membrane extraction of an aqueous sample, based on the assumption that the aqueous phase i s perfectly stirred, The model is in good agreement with the experimen tal benzene extraction results obtained with an efficient agitation me thod such as high-speed magnetic stirring or sonication, The model has also been used to study the effects of various extraction parameters with respect to the sensitivity and response time of the MESI system, Sample agitation facilities analyte mass transport and hence improves both the system sensitivity and the response time, The sensitivity of the extraction method also increases with an increase of the extractio n temperature.