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Loss of H 2 and CO from protonated aldehydes in electrospray ionization mass spectrometry
Author(s) -
Neta Pedatsur,
SimónManso Yamil,
Liang Yuxue,
Stein Stephen E.
Publication year - 2014
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.6968
Subject(s) - chemistry , protonation , fragmentation (computing) , tandem mass spectrometry , electrospray ionization , selected reaction monitoring , mass spectrometry , formic acid , collision induced dissociation , orbitrap , mass spectrum , ion trap , ketene , analytical chemistry (journal) , photochemistry , medicinal chemistry , ion , chromatography , organic chemistry , computer science , operating system
RATIONALE Electrospray ionization mass spectrometry (ESI‐MS) of many protonated aldehydes shows loss of CO as a major fragmentation pathway. However, we find that certain aldehydes undergo loss of H 2 followed by reaction with water in the collision cell. This complicates interpretation of tandem mass (MS/MS) spectra and affects multiple reaction monitoring (MRM) results. METHODS 3‐Formylchromone and other aldehydes were dissolved in acetonitrile/water/formic acid and studied by ESI‐MS to record their MS 2 and MS n spectra in several mass spectrometers (QqQ, QTOF, ion trap (IT), and Orbitrap HCD). Certain product ions were found to react with water and the rate of reaction was determined in the IT instrument using zero collision energy and variable activation times. Theoretical calculations were performed to help with the interpretation of the fragmentation mechanism. RESULTS Protonated 3‐formylchromones and 3‐formylcoumarins undergo loss of H 2 as a major fragmentation route to yield a ketene cation, which reacts with water to form a protonated carboxylic acid. In general, protonated aldehydes which contain a vicinal group that forms a hydrogen bridge with the formyl group undergo significant loss of H 2 . Subsequent losses of CO and C 3 O are also observed. Theoretical calculations suggest mechanistic details for these losses. CONCLUSIONS Loss of H 2 is a major fragmentation channel for protonated 3‐formychromones and certain other aldehydes and it is followed by reaction with water to produce a protonated carboxylic acid, which undergoes subsequent fragmentation. This presents a problem for reference libraries and raises concerns about MRM results. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.