On-line derivatization gas chromatography with furan chemical ionization tandem mass spectrometry for screening of amphetamines in urine

A simple alternative method with minimal sample pretreatment is investigated for screening of amphetamines in small volume (using only 20 μL) of urine sample. The method is sensitive and selective. The method uses gas chromatography (GC) direct sample introduction (DSI) for on-line derivatization (acylation) of amphetamines to improve sensitivity. Furan as chemical ionization (CI) reagent in conjunction with tandem mass spectrometry (MS/MS) is used to improve selectivity. Low background with sharp protonated molecular ion peaks of analytes is the evidence of improvement in sensitivity and selectivity. Blank urine samples spiked with known amounts of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine and 3,4-methylenedioxyethylamphetamine is analyzed. Selected ion monitoring of the characteristic product ions (m/z 119 + 136 + 150 + 163) using furan CI-MS/MS in positive ion mode is used for quantification. Limits of detection (LOD) between 0.4 and 1.0 ng mL−1 and limits of quantitation (LOQ) between 1.0 and 2.0 ng mL−1 are established. Linear response over the range of 1–1000 ng mL−1 (r2 > 0.997) is observed for all analytes, except for methamphetamine (2.0–1000 ng mL−1). Good accuracy between 86 and 113% and precision ranging from 4 to 18% is obtained. The method is also tested on real samples of urine from suspected drug abusers. This method could be used for screening and determination of amphetamines in urine samples, however needs additional work for full validation.