Structures and Fragmentation Mechanisms of the Ions of Ethanol by Triple Quadrupole Mass Spectrometry

摘要

The low energy (10-25 eV) collisionally activated decomposition of the molecular ion and of some important fragment ions of ethanol, ethanol-OD, and 2,2,2-d3 ethanol has been studied by triple quadrupole mass spectrometry to obtain information regarding the ions' structures and fragmentation pathways. In this technique, ions generated by electron impact in the mass spectrometer ion source are mass selected in the first quadrupole, undergo collisionally activated decomposition (CAD) in the second, RF-only, quadrupole collision cell, and the resulting daughter ions are mass analyzed by the third quadrupole. The unit resolving power of the final quadrupole analyzer is a distinct advantage over other implementations of MS/MS in that structural information contained in deuterated species is readily obtainable. Ethanol ions thus studied include (CH3CH2OH)+, (CH3CHOH)+, (CH2COH)+, (CH2CO)+, (CH3OH)+ and (CH2OH)+. Fragementation mechanisms based on CAD spectra are consistent with the fragmentation of a particular ion's deuterated analogs. The elucidation of the decomposition mechanism leads to an unambiquous assignment of parent ion structure in many cases. The observed dissociations parallel closely those observed in both electron impact and high energy CID in sector instruments. The data suggest that fragmentation reactions which follow electron impact and collisional activation at both high and low energies are at least qualitatively independent of the method of excitation.