High-Throughput and Sensitive Screening by Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry of Diuretics and other Doping Agents

The reliability of ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) for high throughput screening in anti-doping control has been tested. A method to screen for the presence of diuretics and other doping agents in urine has been optimised and validated. The extraction procedure consisted of an alkaline extraction (pH 9.5) with ethyl acetate and salting-out effect (sodium chloride). The extracts were analysed by UPLC-MS/MS. Analysis of 34 forbidden drugs and metabolites was achieved in a total run time of 5 min, using a C₁₈ column (100 mm × 2.1 mm i.d., 1.7 μm particle size) and a mobile phase containing deionised water and acetonitrile with formic acid, with gradient elution at a flow-rate of 0.6 mL min⁻¹. Identification of the compounds was performed by multiple reaction monitoring, using electrospray ionisation in positive- or negative-ion mode. Precursor and product ions were studied for each compound and cone voltage and collision energy were optimised. Due to the different chemical structure of the compounds under study, extraction recoveries varied from less than 10% to 100% depending on the analyte. The limits of detection ranged from 50 ng mL⁻¹ to 200 ng mL⁻¹, and all the compounds comply with the requirements of quality established by the World Anti-doping Agency. Intra-assay precision was evaluated at two concentrations for each compound and, in most cases, a relative standard deviation of the signal ratio lower than 20% was obtained. The method has demonstrated to be reliable when analysing routine samples and the short analysis time resulting from a simple sample preparation and a rapid instrumental analysis allow a fast turn-around time and makes it of great interest for routine anti-doping control purposes.