Comparison of membrane assisted liquid-liquid microextraction devices applied to a series of volatile organic compounds in aqueous environmental matrices

An extraction device has been investigated for the separation and preconcentration of a series of volatile organic compounds (CHCl3, CHCl2Br, CHClBr2 and CHBr3) in aqueous matrices. The device consisted of a microporous membrane system utilising a hollow fibre tube filled with organic solvent directly immersed into the sample solution. The hollow fibre containing 160 mu L organic solvent was immersed in a glass vial with 10 mL capacity, and the extraction took place through diffusive transport between the aqueous sample and the small amount of solvent. For validation of the method, some operational conditions, such as extraction solvent, temperature, stirring rate and separation time, were optimised. Limit of detection was at low ppb levels, with GC-MS analysis under selected ion monitoring (SIM), whereas enrichment factors between 22 and 35 were obtained. Good reproducibility with RSDs between 7.2% and 9.8% and large linear dynamic ranges with R-2 between 0.996 and 0.998 were also achieved. In addition, the performance of the membrane assisted solvent extraction (MASE) system was compared with two existing configurations: a non-porous membrane separation device, as well as with a comparable microporous configuration. The comparison considered the extraction mechanism and the underlying transport processes. The application to real samples showed a good concordance with classical analytical methods.