High performance liquid chromatography with UV detection for the simultaneous determination of sympathomimetic amines using 4-(4,5-diphenyl-1H-imidazole-2-yl)benzoyl chloride as a label

A high performance liquid chromatographic method has been developed for the simultaneous determination of () fenfluramine (Fen) and phentermine (Phen) in addition to three other sympathomimetic amines-ephedrine (E), norephedr ine (NE) and 2-phenylethylamine (2-PEA), using cyclohexylamine (CX) as an i nternal standard in plasma. The compounds were derivatized with 4-(4,5-diph enyl-1H-imidazole-2-yl)benzoyl chloride (DIB-Cl) to give the DIB-derivative s. The derivatives were then separated using an isocratic HPLC system with UV detection. The limits of detection for Fen, Phen, E, NE and 2-PEA in pla sma ranged from 0.32 to 22.9 pmol on column at a signal-to-noise ratio of 3 . The recoveries following alkaline extraction from plasma samples of known concentrations were found to be more than 94% for the studied compounds. T his method might be useful for the screening of the studied sympathomimetic amines in human plasma samples in forensic as well as toxicological studie s. Furthermore, the developed method was modified for the simultaneous dete rmination of Fen and Phen in human and rat plasma using fluoxetine as an in ternal standard. The methods are reproducible and precise. Finally, the two drugs were administered intraperitonealy to rats in combination, and their plasma levels over the investigated time course were successfully determin ed. Copyright (C) 2001 John Wiley & Sons, Ltd.