title: Rapid determination of methandrostenolone in equine urine by isotope dilution liquid chromatography-tandem mass spectrometry.
abstract: Urine samples were spiked with [17-methyl-2H3]methandrostenolone as internal standard and extracted with a mixture of dichloromethane and cyclohexane. The organic phase was concentrated and injected onto a short octyl-silica column (30 mm x 4.6 mm I.D.) for separation of methandrostenolone and 17-epimethandrostenolone. The effluent from the column was connected to a Sciex TAGA 6000E triple quadrupole mass spectrometer equipped with an atmospheric pressure ion source for sampling of ions generated by a heated pneumatic nebulizer with corona discharge ionization. This ion source produced abundant [M + H]+ ions and a weak fragment ion due to loss of water. The protonated molecular ions at m/z 301 and 304 for methandrostenolone, 17-epimethandrostenolone and the internal standard were transmitted to the second quadrupole for collision-induced dissociation. Quantification was obtained by selected reaction monitoring of three daughter ions. Methandrostenolone and 17-epimethandrostenolone were separated by liquid chromatography, but gave identical mass spectra. The method detection limit by injection of a urine extract corresponding to 2.8 ml urine was 180 pg/ml at the 99% confidence level. The precision (relative standard deviation) was 3% at the 16 ng/ml level and the linear dynamic range was at least 3 orders of magnitude. Screening for unknown metabolites in urine after administration of methandrostenolone to horses and humans was accomplished by a parent ion scan of m/z 121, a fragment corresponding to the intact A-ring of the steroids.
authors.affiliation: New York State College of Veterinary Medicine, Cornell University, Ithaca 14850.
authors.forename: O
authors.initials: O
authors.lastname: Edlund
authors.forename: L
authors.initials: L
authors.lastname: Bowers
authors.forename: J
authors.initials: J
authors.lastname: Henion
authors.forename: T R
authors.initials: TR
authors.lastname: Covey
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods; D006736:Horses; D006801:Humans; D007201:Indicator Dilution Techniques; D013058:Mass Spectrometry / Q000379:methods; D008696:Methandrostenolone / Q000652:urine*
chemical_list: D008696:Methandrostenolone