Liquid-phase microextraction and capillary electrophoresis of citalopram, an antidepressant drug

A newly developed disposable device for liquid-phase microextraction (LPME) was evaluated for the capillary electrophoresis (CE) of the antidepressant drug citalopram (CIT) and its main metabolite N-desmethylcitalopram (DCIT) in human plasma. CIT and DCIT were extracted from I mi plasma samples thro ugh hexyl ether immobilised in the pores of a porous polypropylene hollow f ibre and into 25 mul of 20 mM phosphate buffer (pH 2.75) present inside the hollow fibre (acceptor phase). Prior to extraction, the samples were made strongly alkaline in order to promote LPME of the basic drugs. Owing to the high ratio between the volumes of sample and acceptor phase, and owing to high partition coefficients, CIT and DCIT were enriched by a factor of 25 t o 30. In addition, sample clean-up occurred during LPME since salts, protei ns and the majority of endogenic substances were unable to penetrate the he xyl ether layer. Since the extracts were aqueous, they were injected direct ly into the CE instrument. Limits of quantification (S/N=10) for CIT and DC IT in plasma were 16.5 ng/ml and 18 ng/ml respectively, while the limits of detection (S/N=3) were 5 ng/ml and 5.5 ng/ml respectively. This enabled CI T land DCIT) to be analysed within the therapeutic range by LPME-CE and det ection Limits were comparable with previously reported HPLC methods. (C) 20 01 Elsevier Science B.V. All rights reserved.