Simultaneous quantification of amphetamine, opiates, ketamine and relative metabolites in urine for confirmatory analysis by liquid chromatography tandem mass spectrometry

The rise in amphetamine, ketamine and opiates abuse in Taiwan has created a need for a reliable confirmatory assay. A method that combines superficially porous liquid chromatography tandem mass spectrometry (LC–MS/MS) with solid-phase extraction (SPE) was developed for the simultaneous quantification of amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), ketamine, opiates, and their corresponding metabolites in urine. The total run time of the method was 6.7 min including equilibration time. The method was validated in accordance with the European Commission (EC) Decision 2002/642/EC. The within- and between-day precision was below 13.6% and the accuracy ranged from −17.1% to +9.9% for all analytes. Ion suppression was observed but compensated by using deuterated internal standards. No carryover was detected and the analytes were stable at room temperature for 16 h, and for 72 h at 4 °C, and three-thaw cycles. The method was further validated by comparison with a reference gas chromatography–mass spectrometry (GC–MS) method, using 52 authentic urine samples. The results indicated that for the target analytes studied, the LC–MS/MS analysis was as precise, accurate, and specific as the GC–MS method. In conclusion, the present LC–MS/MS method is robust and reliable, and suitable for use as a confirmation assay in the simultaneous urine drug testing and quantification of amphetamines, ketamines, and opiates.