A non-covalent dimer formed in electrospray ionisation mass spectrometry behaving as a precursor for fragmentations

作者：[Anonymous]

来源：Rapid Communications in Mass Spectrometry, 2008, 22(22): 3555-3560.

DOI：10.1002/rcm.3767

A non-covalent-bonded dimer was detected in the positive ion electrospray ionisation (ESI) mass spectra of a synthetic impurity. In tandem mass spectrometry (MS/MS) experiments using collision-induced dissociation (CID), the ion was found to behave as a [M+H](+)-type precursor ion for fragmentation until MS(5). The dimer was probably formed through multi-hydrogen bonds over a proton bridge. When the fragmentation occurred at the center of the bridge, the dimer was broken apart to give monomer fragments at MS(6). However, no corresponding deprotonated dimer [2M-H](-) was found in the negative ion ESI spectra. The dimer was extremely stable, and it could still be observed when a fragmentation voltage of up to 50 V was applied in the ionisation source. The formation of the non-covalent dimer was also found to be instrument-dependent, but independent of sample concentration. Accurate mass measurements of the [2M+H](+) and [M+H](+) ions, and their MS" product ions, provided the basis for assessing the fragmentation mechanism proposed for [2M+H](+). The fragmentation pathway was also illustrated for the deprotonated molecule [M-H](-).

• 出版日期2008-11