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Fragmentation of N‐oxides (deoxygenation) in atmospheric pressure ionization: Investigation of the activation process
Author(s) -
Tong Wei,
Chowdhury Swapan K.,
Chen JinChang,
Zhong Ruyun,
Alton Kevin B.,
Patrick James E.
Publication year - 2001
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.475
Subject(s) - chemistry , deoxygenation , atmospheric pressure chemical ionization , fragmentation (computing) , mass spectrometry , chemical ionization , ionization , chromatography , metabolite , analytical chemistry (journal) , mass spectrum , ion , organic chemistry , catalysis , biochemistry , operating system , computer science
The diagnostic fragmentation of N‐oxides resulting from loss of the oxygen atom (MH + → MH + ‐O) in electrospray and atmospheric pressure chemical ionization (APCI) mass spectra was investigated. When the temperature of the heated capillary tube was elevated, the ratio of the intensity of the [MH + − 16] fragment to the precursor ion (MH + ) increased. This ‘deoxygenation’ process was associated with thermal activation and did not result from collisional activation in the desolvation region of the API source. Although the extent of ‘deoxygenation’ is compound‐dependent, it can provide evidence for the presence of an N‐oxide in a sample and can be used to distinguish N‐oxides from hydroxylated metabolites (Ramanathan et al. Anal. Chem. 2000; 72: 1352). To demonstrate the practical application of thermal fragmentation of N‐oxides, liquid chromatography (LC)/APCI‐MS was used to distinguish an N‐oxide drug from its hydroxylated metabolite in an unprocessed rat urine sample, despite the fact that the drug and its metabolite were not fully resolved by HPLC. Copyright © 2001 John Wiley & Sons, Ltd.