GC-MS determination of amphetamines in human urine

An analytical method for the simultaneous determination of amphetamine (AP), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-methamphetamine ( MDMA), and 3,4-methylenedioxy-ethamphetamine ( MDEA) in urine, using gas chromatography - mass spectrometry ( GC - MS), is proposed. The analytes were subjected to liquid - liquid extraction with 4: 1 (v/v) methylene chloride/isopropanol at pH 12, and derivatized with pentafluoropropionic anhydride (PFPA) and ethyl acetate. Calibration curves for the five analytes in methanol and urine were constructed over the range 0.5 - 5.0 mu g center dot ml(-1), using their respective pentadeuterated analogues as internal standards. The average extraction recoveries from the urine were higher than 91% for the five amphetamines. The limits of detection and quantitation achieved were 2.02 and 6.74 ng center dot ml(-1) for AP; 0.56 and 1.88 ng center dot ml(-1) for MA; 2.74 and 9.13 ng center dot ml(-1) for MDA; 2.95 and 9.85 ng center dot ml(-1) for MDMA; and 5.41 and 18.03 ng center dot ml(-1) for MDEA. The accuracy was in the range +/- 4% and the coefficients of variation were less than 9% for all analytes. The analysis of real urine samples with the proposed method provided 24 positives for amphetamines, with the following average concentrations: 0.56 mu g center dot ml(-1) for AP, 6.78 mu g center dot ml(-1) for MA, 0.90 mu g center dot ml(-1) for MDA, 8.78 mu g center dot ml(-1) for MDMA, and 1.13 mu g ml(-1) for MDEA.