A convenient derivatization method for the determination of amphetamine and related drugs in urine

The most commonly abused CNS stimulant in Sweden is amphetamine followed by phenmetrazine. Methamphetamine and phentermine are rarely seen but still of interest. This paper describes a rapid and sensitive method for the analysis of amphetamine, methamphetamine, phentermine, and phenmetrazine in urine using gas chromatography with nitrogen sensitive detection (GC-NPD). The method also qualitatively determines ephedrine and norephedrine. The derivatization was carried out at room temperature with methyl chloroformate to form the corresponding carbamates. Other chloroformate analogues were also tested. Because methyl chloroformate is relatively stable in the presence of water the extraction and derivatization were combined in one step. A concentration step was not necessary to achieve sufficient sensitivity. The recovery was more than 83% for all analytes. The LOQ was 0.05, 0.03, 0.07 and 0.01 (microgram/mL urine) for amphetamine, methamphetamine, phentermine and phenmetrazine respectively. The cut-off was set at 0.2 microgram/mL. The within-day and between-day relative standard deviation (RSD) for amphetamine were 2.2% (n = 9) and 4.7% (n = 5) respectively. There was a good quantitative correlation (r2 = 0.995) between GC-NPD using chloroformate derivatives and gas chromatography-mass spectrometry (GC-MS) using trifluoroacetic anhydride (TFA) as derivatizing agent for the determination of amphetamine in authentic samples.