THE DETERMINATION OF METHADONE AND METABOLITES IN HUMAN URINE BY HPLC WITH ULTRAVIOLET, AND PARTICLE-BEAM MASS-SPECTROMETRIC DETECTION

Liquid chromatography coupled to Mass Spectrometry has been used to identify and quantitate methadone and two of its metabolites following a normal phase separation on a cyano-phase column. Solvent extraction was used to recover the target compounds from urine at the optimal pH of 10, (recovery: 88%, methadone; 75%, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP). Routine analysis may be performed using UV detection at 290 nm. However, for greater selectivity and identification of eluates mass spectrometry is preferred. In the urine samples studied the methadone/EDDP ratio varied from 1:1 to 1:10. Two samples showed evidence for the presence of 1,5-dimethyl-3,3-diphenplpyrrolidone (DDP). Methadone may be detected selectively at m/z = 223 but the ion abundance is weak. Detection using the base peak m/z = 72 is preferred because of the increased sensitivity it confers although selectivity of detection is lost.