A validated SPME-GC–MS method for simultaneous quantification of club drugs in human urine

Abstract

A solid-phase microextraction-gas chromatographic–mass spectrometric (SPME-GC–MS) method has been developed and validated for measuring four club drugs in human urine. These drugs include gamma-hydroxybutyrate (GHB), ketamine (KET), methamphetamine (MAMP), and methylenedioxymethamphetamine (MDMA). These drugs are referred to as ‘club drugs’ because of their prevalence at parties and raves. Deuterium labeled internal standards for each of the four drugs was included in the assay to aid in quantitation. The drugs were spiked into human urine and derivatized using pyridine and hexylchloroformate to make them suitable for GC–MS analysis. The SPME conditions of extraction time/temperature and desorption time/temperature were optimized to yield the highest peak area for each of the four drugs. The final SPME parameters included a 90 °C extraction for 20 min with a 1 min desorption in the GC injector at 225 °C using a splitless injection. All SPME work was done using a 100 μm PDMS fiber by Supelco. The ratio of pyridine to hexylchloroformate for derivatization was also optimized. The GC separation was carried out on a VF-5ht column by Varian (30 m, 0.25 mm i.d., 0.10 μm film thickness) using a temperature program of 150–270 °C at 10 °C/min. The instrument used was a ThermoFinnigan Trace GC-Polaris Q interfaced with a LEAP CombiPal autosampler. The data was collected by using extracted ion chromatograms of marker m/ z values for each drug from the total ion chromatograms (TIC) (full scan mode). Calibration curves with R 2 > 0.99 were generated each day using the peak area ratios (peak area drug/peak area internal standard) versus concentration. The validated method resulted in intra-day and inter-day precision (% R.S.D.) of less than 15% and a % error of less than 15% for four concentrations in the range of 0.05–20 μg/mL (MAMP) and 0.10–20 μg/mL (GHB, KET, and MDMA). This method has the advantage of an easy sample preparation with acceptable accuracy and precision for the simultaneous quantification of these four drugs of abuse and shows no interference from the urine matrix.