Quantitation of l-α-acetylmethadol and its metabolites in human serum by capillary gas—liquid chromatography and nitrogen detection

Abstract

A procedure is described for the simultaneous measurement of l-α-acetylmethadol and its two pharmacologically active metabolites: noracetylmethadol and dinoracetylmethadol. In the method an intramolecular conversion reaction of the two metabolites to their amide configuration is utilized. The reaction is performed while the metabolites are still in the serum. Following solvent extraction the samples are analyzed by capillary gas—liquid chromatography coupled with nitrogen detection. Quantitation is achieved by internal standardization. The lower limit of sensitivity is 5 ng/ml in serum. Absolute sensitivity is 0.1 ng for all three compounds. The advantages over other procedures are: (1) speed due to the single extraction step; (2) increased recovery of noracetylmethadol and dinoracetylmethadol due to decreased polarity of the amides; (3) greater stability of the metabolites in the amide configuration; (4) better chromatographic quantitation and separation because detector response for the amides is greater than it is for the original configuration of the metabolites and the area of the chromatographic tracing is free of interfering substances.