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A simple to construct and operate, "dip-in" electromembrane extraction (EME) probe directly coupled to electrospray ionization-mass spectrometry (ESI-MS) for rapid extraction and real time analysis of various analytes was developed. The setup demonstrated that EME-MS can be used as a viable alternative to conventional protein precipitation followed by liquid chromatography–mass spectrometry (LC–MS) for studying drug metabolism. Comparison of EME-MS with LC–MS for drug metabolism analysis demonstrated for the first time that real time extraction of analytes by EME is possible. Metabolism kinetics were investigated for three different drugs: amitriptyline, promethazine, and methadone. By comparing the EME-MS extraction profiles of the drug substances and formed drug metabolites with the metabolism profiles obtained by conventional protein precipitation followed by LC–MS good correlation was obtained with only very limited time delay in the extraction. The results indicate that, by tuning the electromembrane properties, for example, by optimizing the extraction voltage, extremely fast extraction kinetics can be obtained. A metabolic profile could be generated while the drug was metabolized offering a significant time saving as compared to conventional LC–MS where laborious protein precipitation or other sample pretreatments are required before analysis. This makes the developed EME-MS setup a highly promising sample preparation method for various kinds of applications where fast and real-time analysis of analytes is of interest. [ABSTRACT FROM AUTHOR]

An automated analyte electroextraction and preconcentration system, which was used as the front end for a liquid chromatography-electrospray mass spectrometry instrument, is described. The extraction was based on driving the anionic analytes across a polymer inclusion membrane by application of a potential of 200 V to the cell. Five milliliters (5 mL) of sample were passed through a flow-through cell at a flow rate of 0.2 mL/min containing a membrane 20 μm thick. This consisted of 75% cellulose triacetate as base polymer, 12.5% of tris(2-ethylhexyl)phosphate as plasticizer, and 12.5% of Aliquat 336 as cationic carrier. The target analytes were enriched in 20 μL of a stagnant acceptor solution prior to online LC/MS analysis. The performance of the system was demonstrated for the determination of chlorinated phenoxyacetic acid herbicides in spiked river water. Enrichment factors of ~200 were achieved with recoveries of typically 99% and precision values of typically 5%. The limit of detection (LOD) values were found to be between 0.03 ng/mL to 0.08 ng/mL. [ABSTRACT FROM AUTHOR]