Analysis of Stimulants in Sweat and Urine Using Disposable Pipette Extraction and Gas Chromatography Coupled to Mass Spectrometry in the Context of Doping Control

Abstract

Abstract Urine is initially collected from athletes to screen for the presence of illicit drugs. Sweat is an alternative sample matrix that provides advantages over urine including reduced opportunity for sample adulteration, longer detection-time window and non-invasive collection. Sweat is suitable for analysis of the parent drug and metabolites. In this study, a method was developed and validated to determine the presence of 13 amphetamine- and cocaine-related substances and their metabolites in sweat and urine using disposable pipette extraction (DPX) by gas chromatography coupled to mass spectrometry. The DPX extraction was performed using 0.1 M HCl and dichloromethane:isopropanol:ammonium hydroxide (78:20:2, v/v/v) followed by derivatization with N-methyl-N-(trimethylsilyl) trifluoroacetamide at 90°C for 20 min. DPX extraction efficiencies ranged between 65.0% and 96.0% in urine and 68.0% and 101.0% in sweat. Method accuracy was from 90.0% to 104.0% in urine and from 89.0% to 105.0% in sweat. Intra-assay precision in urine and in sweat were <15.6% and <17.8%, respectively, and inter-assay precision ranged from 4.70% to 15.3% in urine and from 4.05% to 15.4% in sweat. Calibration curves presented a correlation coefficient –0.99 for all analytes in both matrices. The validated method was applied to urine and sweat samples collected from 40 professional athletes who knowingly took one or more of the target illicit drugs. Thirteen of 40 athletes were positive for at least one drug. All the drugs detected in the urine were also detected in sweat samples indicating that sweat is a viable matrix for screening or confirmatory drug testing.