Analysis of sibutramine metabolites as N-trifluoroacetamide and O-trimethylsilyl derivatives by gas chromatography–mass spectrometry in urine

A method for identifying the metabolites of sibutramine 1-(4(chlorophenyl)-N,N-dimethyl-α-(2-methylpropyl))cyclobutanemethanamine) in urine, utilizing a double derivatization strategy, with N-methyl-N-(trimethylsilyl)-trifluoroacetamide and N-methyl-bis-(trifluoroacetamide), in gas chromatography/mass spectrometry is proposed. This methodology results in mass spectra with at least three fragments in abundance superior to 20%, attending the World Anti-Doping Agency identification criteria for qualitative assays. The characterization of the derivatives was obtained through two ionization modes: Chemical Ionization and Electron Impact ionization, both in full scan mode. Sibutramine was administered to 5 (five) volunteers and the excretion profile followed for 92 h. Routine analytical, hydroxy-cyclobutane-bis-nor-sibutramine which becomes the more abundant metabolite in the first 10 h and hydroxy-isopropyl-bis-nor-sibutramine which becomes the most abundant after 40 h, were proposed for doping monitoring.