Use of flat-sheet membrane extraction with a sorbent interface for solvent-free determination of BTEX in water

An analytical method for solvent-free determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using flat-sheet membrane extraction with a sorbent interface (MESI) coupled to GC–MS was established by optimizing the flow rates of the donor (20 ml water) and acceptor (helium) phases and extraction temperature. BTEX compounds permeated through a nonporous silicone membrane and evaporated into the acceptor phase were purged into a cryofocusing trap (−30 °C) with helium gas. Enriched compounds were thermally desorbed into a capillary gas chromatograph and detected with a mass spectrometer. The optimum flow rates of the donor and acceptor phases were set at 1.5 and 55 ml min−1, respectively, and the temperature of the membrane extraction module was maintained within the 28–30 °C range. The method as established showed low method detection limits (MDLs:∼0.1 μg l−1) and highly linear calibration curves (r2>0.998) for all of the four compounds. High repeatability (relative standard deviation <∼5%) and a reasonably high extraction recovery (62–78%), after a single pass of the sample through the extraction module, also were established. Further, the methodʹs high compatibility with the purge and trap (P&T) method indicates its applicability to field measurement. Other advantages include rapidity, simplicity, and a ready extendibility to automated on-line monitoring.