A rapid and convenient LC/MS method for routine identification of methamphetamine/dimethylamphetamine and their metabolites in urine

A rapid and sensitive LC/MS method was developed for the simultaneous analysis of N,N-dimethylamphetamine (DMA), N,N-dimethylamphetamine N-oxide (DMANO), methylamphetamine (MA) and amphetamine (A) in urine samples. Employing an Alltech C18 column for solid phase extraction followed by LC/MS analysis using an Alltech Platinum EPS C18 column with a mixture of ammonium formate (0.01 M, pH 3) and acetonitrile (77:23, v/v) as mobile phase at a flow rate of 0.2 mL/min, simultaneous identification and quantitation of A, MA, DMA and DMANO in urine can be achieved using a 5-min chromatographic run. The calibration ranges were 0.10–3.0 μg/mL for DMANO, 0.05–3.0 μg/mL for DMA and 0.05–5.0 μg/mL for both MA and A. The intra-, inter-day precision and accuracy for all analytes, spiked at three different concentrations in quality control samples, were in the ranges of 1.7–8.6, 4.1–10.0, −11.6 to 12.9%, respectively. The newly developed method was applied to the analysis of urine samples obtained from 118 suspected MA/DMA abusers, with the presence of MA confirmed in their urine samples under the drug-use surveillance program. Of these 118 samples, 43 were found to contain DMANO and 11 with both DMANO and DMA.