Identification and quantification of the osmodiuretic mannitol in urine for sports drug testing using gas chromatography-mass spectrometry.

The osmodiuretic mannitol can be potentially misused in sports, owing to its urine diluting effect and the possibility to decrease bodyweight. To reveal a doping offence, resulting urinary mannitol concentrations after a prohibited intravenous application and a permitted oral intake have to be differentiated. Therefore, a reliable gas chromatography-mass spectrometry (GC-MS) method was established based on peracetyl derivatives of the analytes. All possible hexitols (allitol, galactitol, iditol, altritols, sorbitol and mannitol) that can occur in human urine were separated and identified on a phenyl-methylpolysiloxane column (HP-5MS) within 10.75 min, and the method demonstrated its capability for quantification purposes. The lower limit of detection and lower limit of quantification were estimated at 0.9 microg mL(-1) and 2.4 microg mL(-1), respectively, and the assay was validated for mannitol and sorbitol regarding the parameters specificity, linearity, intra- (<10%) and inter-day precision (<15%) and accuracy (92-102%). To investigate urinary mannitol concentrations after oral intake the method was applied to an excretion study, providing a mean urinary excretion of mannitol of 19.5%. Comparison of theoretically expected urinary levels after a common therapeutic dose of mannitol and preliminary results on physiological urinary mannitol levels were promising, regarding a threshold level for mannitol that can be utilised for doping control purposes.