Automated headspace solid-phase microextraction and in-matrix derivatization for the determination of amphetamine-related drugs in human urine by gas chromatography-mass spectrometry

An automated extraction and determination method for the gas chromatography (GC)-mass spectrometry (MS) analysis of amphetamine-related drugs in human urine is developed using headspace solid-phase microextraction (SPME) and in-matrix derivatization. A urine sample (0.5 mL), potassium carbonate (5M, 1.0 mL), sodium chloride (0.5 g), and ethylchloroformate (20 μL) are put in a sample vial. Amphetamine-related drugs are converted to ethylformate derivatives (carbamates) in the vial because amphetamine-related drugs in urine are quickly reacted with ethylchloroformate. An SPME fiber is then exposed at 80°C for 15 min in the headspace of the vial. The extracted derivatives to the fiber are desorbed by exposing the fiber in the injection port of a GC-MS. The calibration curves show linearity in the range of 1.0 to 1000 ng/mL for methamphetamine, fenfluramine, and methylenedioxymethamphetamine; 2.0 to 1000 ng/mL for amphetamine and phentermine; 5.0 to 1000 ng/mL for methylenedioxyamphetamine; 10 to 1000 ng/mL for phenethylamine; and 50 to 1000 ng/mL for 4-bromo-2,5-dimethoxyphenethylamine in urine. No interferences are found, and the time for analysis is 30 min for one sample. Furthermore, this proposed method is applied to some clinical and medico-legal cases by taking methamphetamine. Methamphetamine and its metabolite amphetamine are detected in the urine samples collected from the patients involved in the clinical cases. Methamphetamine, amphetamine, and phenethylamine are detected in the urine sample collected from the victim of a medico-legal case. © 2002 Oxford University Press.