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Formation of deprotonated molecules [M—H] − of α‐tocopherol under fast‐atom bombardment conditions
Author(s) -
Takayama Mitsuo
Publication year - 1994
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1290080405
Subject(s) - chemistry , proton affinity , deprotonation , fast atom bombardment , molecule , ion , proton , analytical chemistry (journal) , protonation , organic chemistry , physics , quantum mechanics
The formation of deprotonated molecules, [M—H] − , of α‐tocopherol under fast‐atom bombardment (FAB) conditions has been discussed on the basis of a proton subtraction reaction between analyte and matrix molecules. The use of proton‐accepting matrices such as diethanolamine (DEA) and pentamethyleneglycol (PMG) gave higher intensities of the [M—H] − ion and more definitive spectral data than when other matrices, a 1:2 (v/v) mixture of thioglycerol (TG) and dithiothreitol (DTT), or m ‐nitrobenzylalcohol ( m ‐NBA), were used. The order of proton acceptability evaluated for the matrices used was DEA>PMG>DTT> m ‐NBA. It was concluded that the proton acceptability, which is measured by gas‐phase basicity or proton affinity, is a most important factor for the formation of both [M + H] + and [M—H] − ions under FAB conditions. Further, the formation of molecular ions, M +· , under FAB conditions and the formation of [M—H] − ions by electron impact have been discussed by using α‐tocopherol.