Characterisation of sulphoxides by atmospheric pressure ionisation mass spectrometry.
An observation that a series of proprietary compounds containing a methyl thiophenyl group all underwent metabolic S-oxidation, and that the product ion spectra of the resulting S-oxides showed methyl radical loss under low-energy atmospheric pressure ionisation tandem mass spectrometry (API-MS/MS) conditions, has led to an investigation of the fragmentation of commercially available sulphoxides. The phenyl methyl sulphoxides studied do lose methyl radicals under MS/MS conditions on triple quadrupole mass spectrometers. In addition, the phenyl sulphoxides, with simple substituents other than a methyl group, also showed a tendency to lose the substituent as a radical. It was concluded that radical loss from these simple sulphoxides was characteristic of S-oxidation of these molecules. Radical losses, such as those reported here, are used in-house to distinguish S-oxidation from N- and C-oxidation in metabolism studies.
Wright
Patricia
P
Department of Pharmacokinetics, Dynamics and Metabolism, Pfizer Global Research and Development, Ramsgate Road, Sandwich CT13 9NJ, UK. Pat.Wright@Pfizer.com
Alex
Alexander
A
Gibson
Drew
D
Jones
Russell
R
Macrae
Paul
P
D000818:Animals; D001274:Atmospheric Pressure; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008862:Microsomes, Liver / Q000737:chemistry; D010084:Oxidation-Reduction; D051381:Rats; D013454:Sulfoxides / Q000737:chemistry*
D013454:Sulfoxides