Determination of maprotiline and N-desmethylmaprotiline from biological fluids by HPLC

A reversed-phase high-performance liquid chromatographic method has been developed for the simultaneous quantitation of maprotiline and its desmethylated metabolite from biological fluids. In this method, the samples were washed with hexane at acidic pH and then extracted with the same solvent at alkaline pH in the presence of an amine carrier. The drugs were eluted from the C18 column with acetonitrile (30%) in phosphate buffer (pH 2.5) and detected by their UV-absorbances at 205 nm. Peak identification was based on retention times and desmethyldoxepine was used as an internal standard for quantitation. Possible interferences were few; sensitivity (detection limit, 11 nmoles/L) and reproducibility (CV 2-2.5%) were good. Only about 10 minutes of chromatographic time was needed for one sample. Application for screening toxic drugs is suggested and briefly discussed.