Development and validation of a solid-phase extraction gas chromatography-mass spectrometry method for the simultaneous quantification of methadone, heroin, cocaine and metabolites in sweat

Abstract

A sensitive and specific method is presented to simultaneously quantify methadone, heroin, cocaine and metabolites in sweat. Drugs were eluted from sweat patches with sodium acetate buffer, followed by SPE and quantification by GC/MS with electron impact ionization and selected ion monitoring. Daily calibration for anhydroecgonine methyl ester, ecgonine methyl ester, cocaine, benzoylecgonine (BE), codeine, morphine, 6-acetylcodeine, 6-acetylmorphine (6AM), heroin (5-1000 ng/patch) and methadone (10-1000 ng/patch) achieved determination coefficients of >0.995, and calibrators quantified to within +/-20% of the target concentrations. Extended calibration curves (1000-10,000 ng/patch) were constructed for methadone, cocaine, BE and 6AM by modifying injection techniques. Within (N = 5) and between-run (N = 20) imprecisions were calculated at six control levels across the dynamic ranges with coefficients of variation of <6.5%. Accuracies at these concentrations were +/-11.9% of target. Heroin hydrolysis during specimen processing was <11%. This novel assay offers effective monitoring of drug exposure during drug treatment, workplace and criminal justice monitoring programs.

Fig. 1

Merged extracted ion chromatograms from a sweat patch spiked at the limit of quantification (LOQ in bracket, ng/patch) for all analytes: anhydroecgonine methyl ester (AEME), ecgonine methyl ester (EME), methadone, cocaine, benzoylecgonine (BE), codeine, morphine, 6-acetylcodeine (6AC), 6-acetylmorphine (6AM), heroin. The quantifying ion is denoted in bold

Fig. 2

Merged extracted ion chromatograms from a sweat patch worn for five days by a heroin user under 120 mg daily methadone maintenance treatment. Analyte concentrations are presented as ng/patch: anhydroecgonine methyl ester (AEME), ecgonine methyl ester (EME), methadone, cocaine, benzoylecgonine (BE), morphine, 6-acetylcodeine (6AC), 6-monoacetylmorphine (6AM), heroin. The patch contained no codeine. Methadone and cocaine were quantified from a split injection on the higher calibration curve