Simultaneous determination of imipramine, desipramine, and their 2-hydroxy metabolites in plasma by ion-pair reversed-phase high-performance liquid chromatography with amperometric detection.

An ion-pair reversed-phase high-performance liquid chromatographic (HPLC) method, using an electrochemical detector, is presented for the simultaneous and rapid quantitation of imipramine desipramine, and their 2-hydroxylated metabolites in plasma. The drugs are extracted from 1 ml of plasma at pH 9.7 with ether, back-extracted into 0. M HCl, and reextracted into ether following alkalinization. An efficient electrochemical oxidation reaction at the detector electrode affords a low detection level of approximately 5 ng/ml in a mobile phase of acetonitrile--acetate buffer (40:60) containing 0.005 M heptanesulfonate. Patient data are presented as correlations between the plasma level of each hydroxy metabolite and its respective parent compound. The method is applicable to the laboratory experienced in HPLC.