Simultaneous determination of beta-blocking agents and diuretics in doping analysis by liquid chromatography/mass spectrometry with scan-to-scan polarity switching

A previously described method for the screening of 18 diuretics and probenecid was substantially extended with 21 beta-blockers and 8 other diuretics allowing simultaneous determination of diuretics and beta-adrenergic blocking agents in human urine. Analysis was performed using an ion trap instrument with an electrospray ionisation (ESI) interface after liquid/liquid extraction with ethyl acetate. Full-scan MS and full-scan MS2 were applied in combination with scan-to-scan polarity switching. All compounds were separated in less than 22 min. The detection limits for the diuretics were between 5 and 100 ng/mL and for the beta-adrenergic blocking agents were between 5 and 500 ng/mL. The excretion of carvedilol was followed after intake of one tablet of Dimitone. Other doping agents including strychnine, norbuprenorphine and mesocarb hydroxysulfate could also be detected with this method.