Rapid GC-MS confirmation of amphetamines in urine by extractive acylation

Amphetamine and related derivatives are widely abused central- and psychostimulants. Detection of certain derivatives, such as methcathinone, by commonly available immunoassay screening techniques is insufficient. Multi-analyte confirmations for amphetamine type stimulants are therefore required, but traditional gas chromatography-mass spectrometry methods necessitate lengthy analytical procedures with prolonged sample turn-around times. A validated rapid GC-MS assay for urinary confirmation of amphetamine, methamphetamine, methcathinone, ephedrine, norephedrine, methylenedioxyamphetamine, methylenedioxymethamphetamine, methylenedioxyethylamphetamine and N-methyl-1-(3,4 methylenedioxyphenyl)-2-butanamine is reported. The method entailed in situ derivatization of urine specimens by extractive acylation with pentafluoropropionic anhydride, followed by rapid chromatography on a microbore capillary column. Analytes were separated in less than 3 min and quantified simultaneously by selected-ion monitoring using stable isotope substituted internal standards. The total instrument cycle-time was 6 min per sample. The limits of detection were between 1.5 ng/mL and 6.25 ng/mL for the various analytes. Intermediate precision and accuracy were in the range of 6.3-13.8% and 90.5-107.3% for the respective analytes at the lower limit of quantitation, and between 5.8-12.6% and 95.4-103.1% for the high control. Long-term storage of methcathinone positive specimens at -20 degrees C proved insufficient stability of this analyte. The proposed assay is precise and accurate for confirmation of amphetamine and derivatives in urine. The complementary approach of extractive-derivatization and fast GC-MS analysis is especially applicable in routine clinical settings where reduced sample turn-around times are required. Further investigation of cathinone as a possible metabolite of methcathinone is warranted, based on results from analyzed authentic urine samples.