Fragmentation of trimethoprim and other compounds containing alkoxy-phenyl groups in electrospray ionisation tandem mass spectrometry

Eur. J. Mass Spectrom. 11, 73–82 (2005)
DOI: 10.1255/ejms.719

Fragmentation of trimethoprim and other compounds containing alkoxy-phenyl groups in electrospray ionisation tandem mass spectrometry

Christine Eckers,^a John J. Monaghan^b and Jean-Claude Wolff^a,*
^aGlaxoSmithKline, Analytical Sciences, Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, UK. E-mail: Jean-Claude.2.Wolff@gsk.com
^bUniversity of Edinburgh, School of Chemistry, West Mains Road, Edinburgh, EH9 3JJ, UK

ABSTRACT:

This work describes electrospray ionisation tandem mass spectrometry studies of trimethoprim and a series of structurally similar compounds containing alkoxy-phenyl groups; using accurate mass measurement to confirm the proposed fragmentations. Radical cations were observed in the spectra obtained for some of the compounds, as well as uncommon fragmentations showing losses of CH₄ and C₂H₆, whereas other compounds showed the formation of even electron ions. Possible structures for the fragment ions have been proposed and explanations for the different types of fragmentations based on the structures of the compounds. In addition an alternate structure for a fragment ion previously reported for tandem mass spectrometry of trimethoprim has been proposed based on accurate mass measurement.

Keywords: electrospray ionisation, tandem mass spectrometry, accurate mass, fragmentation pathway, trimethoprim, alkoxyphenyl compounds, radical fragment ions

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