Isocratic liquid chromatographic method for the determination of amoxapine and its metabolites

An isocratic reverse-phase liquid chromatographic method for the determination of amoxapine and its major metabolites in human plasma utilizing UV detection is described. Plasma samples were extracted with ethyl acetate after pH adjustment. The reconstituted extracts were injected onto a cyanopropylsilane column and eluted with a mobile phase consisting of 65% acetonitrile and 35% sodium acetate buffer, 0.03 M and pH 6. The minimum detectable limit was less than 10 ng/mL of plasma. Possible interferences from other drugs which might be administered concurrently were studied. The reproducibility and precision of the method are demonstrated by the analysis of samples containing 25-600 ng/mL of plasma. The method is being applied successfully in our laboratory for the analysis of plasma from patients receiving amoxapine.