Simultaneous gas chromatography/mass spectrometry assay of methadone and 2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in urine

An efficient extraction and gas chromatography/mass spectrometry (GC/MS) procedure has been developed for the simultaneous determination of methadone and 2-ethyl-1,5-dimethyl-3,3-diphenylpyrrolidine in urine samples. The merits of this procedure include (1) effective high-volume sample processing; (2) excellent gas chromatography characteristics; (3) high precision for quantitative methadone determination--1.0% coefficient of variation (CV) for GC/MS injection replicates and 1.2% for extraction replicates; (4) excellent linearity within the range (0 to 1200 ng/mL) studied; and (5) adequate detection limits (50 ng/mL) for most practical purposes. The detection limit for methadone may be improved 40-fold by using a different internal standard.