Abstract

An analytical method for solvent-free determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in water using repetitive membrane extractions coupled to cryofocusing and GC-MS was derived. BTEX compounds that permeated through a nonporous silicone membrane from the aqueous phase and evaporated into the acceptor phase were purged into a cryofocusing trap (-100 ℃) with helium gas. The BTEX compounds,thus enriched in the trap, were thermally desorbed into a capillary column GC and detected using an MS. The flow rate of the donor phase (30 mL water) was set at 10 mL/min, and membrane extractions, accomplished by returning the water drained from the extraction module to the sample container, were repeated three times at 20 ± 2 ℃. Although recoveries (%) were variable, from the highest for benzene (approximately 80%) to the lowest for ethylbenzene and xylenes (3.5-10%), the method showed satisfactory precision (RSD 2.2-10%)with good-linearity calibration curves (r^2 0.9976-0.9997 in 1-100 μg/L range) for all of the compounds. The method detection limits (MDLs) ranged from 0.16 to 1.8 μg/L. The results showed the method’s advantages such as short analysis time and overall simplicity without solvent compared to the conventional techniques.