Solid-phase extraction with liquid chromatography and ultraviolet detection for the assay of antidepressant drugs in human plasma

A solid-phase extraction (SPE) method for sample clean-up followed by a rev ersed-phase high-performance liquid chromatography (HPLC) procedure for the assay of five antidepressant drugs (trazodone, doxepin, desipramine, mapro tiline and imipramine) is reported. The drugs were recovered from plasma bu ffered at a suitable pH using C18 Bond-Elut cartridges and mixtures of meth anol-aqueous buffer as washing and elution solvents. The recoveries of the drugs using other sorbent materials (C8, C2, cyclohexyl, cyanopropyl and ph enyl Bond Elut and copolymer HLB waters cartridges) were also examined. The selectivity of SPE was examined by using spiked plasma samples and the CH cartridge gave rise to the cleanest extracts. Cyclohexyl cartridges were co nditioned successively with 2 ml of methanol and 1 ml of acetic acid-sodium acetate buffer (0.1 M, pH 4.0). Plasma sample was buffered at pH 4.0 and t hen applied to the sorbent. The washing step was performed subsequently wit h 1.5 ml of acetate buffer (0.1 M, pH 4.0), 100 mu l of acetonitrile and 1 ml of methanol-acetate buffer (30:70, v/v). Finally, the analytes were elut ed with 0.5 ml of methanol-acetate buffer (70:30, v/v). The extract was eva porated to dryness, reconstituted in mobile phase, and chromatographed on a reversed-phase C18 column with ultraviolet detection at 215 nm. The recove ries of trazodone, doxepin, desipramine, maprotiline and imipramine from sp iked plasma samples using the CH cartridge were 58 2, 84 3, 83 3, 83 3 and 82 2%, respectively. The within-day and between-day repeatabilities were lo wer than 6% and 9%, respectively. The linearity of calibrations for the fiv e antidepressants was between 0.005 and 2 mu g/ml. The limits of detection were 1 ng/ml for trazodone, doxepin and desipramine and 2 ng/ml for maproti line and imipramine. (C) 1999 Published by Elsevier Science B.V. All rights reserved.