Structure of muramic acid TMS derivative mass spectrum's base ion (m/z=185) used for quantification of bacterial peptidoglycan.

The use of trimethylsilyl (TMS)-derivatisation for determining muramic acid in environmental and clinical samples by gas chromatography-mass spectrometry provides high detection sensitivity; however, questions have been raised as concerns the chemical structure of the entity giving the strong signal of m/z 185. In the present communication we present evidence that this entity results from the formation of a lactam structure of muramic acid upon derivatisation.