alpha-Benzyl-N-methylphenethylamine (BNMPA), an impurity of illicit methamphetamine synthesis: I. Physical characterization and GC-MS analysis of BNMPA and anticipated metabolites in urine.

alpha-Benzyl-N-methylphenethylamine (BNMPA) is an impurity of illicit methamphetamine synthesis. We synthesized BNMPA and three of its anticipated metabolites: N-demethyl-alpha-benzyl-phenethylamine, 1,3-diphenyl-2-propanone, and 1,3-diphenyl-2-propanol. The purity and structure of these compounds and their heptafluorobutyric anhydride (HFBA) derivatives were confirmed by melting point, gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance. A GC-MS method to detect these compounds in urine, using liquid-liquid extraction and derivatization with HFBA, was developed. Interference studies showed BNMPA and its proposed metabolites to be well-resolved from other common phenethylamine drugs and Health and Human Services-Forensic Urine Drug Testing required analytes. The limit of detection of BNMPA and its metabolites was 2.5 ng/mL; the limit of quantitation (LOQ) of the four compounds was 25 ng/mL. The calibration curves were generally linear from 25 to 500 ng/mL. Typical within-run coefficients of variation (CVs) at the LOQ ranged from 13 to 20% (n = 8). Between-run CVs over 1 month at 25 ng/mL were from 9 to 28%, and at 500 ng/mL, they were from 2.6 to 3.9%. The detection of BNMPA or its metabolites in urine samples may provide a marker of use of illicitly synthesized methamphetamine.