Loss of H2 and CO from protonated aldehydes in electrospray ionization mass spectrometry. (23rd July 2014)

• Record Type: Journal Article
• Authors: Neta, Pedatsur; Simón‐Manso, Yamil; Liang, Yuxue; Stein, Stephen E.
• Is Part Of: Rapid communications in mass spectrometry. Volume 28:Number 17(2014)
• Page Start: 1871
• Page End: 1882
• Publication Date: 2014-07-23
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6968
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6968-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>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<sub>2</sub> 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.</p> </sec> <sec id="rcm6968-sec-0002" sec-type="section"> <title>METHODS</title> <p>3‐Formylchromone and other aldehydes were dissolved in acetonitrile/water/formic acid and studied by ESI‐MS to record their MS<sup>2</sup> and MS<sup>n</sup> 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.</p> </sec> <sec id="rcm6968-sec-0003" sec-type="section"> <title>RESULTS</title> <p>Protonated 3‐formylchromones and 3‐formylcoumarins undergo loss of H<sub>2</sub> 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<sub>2</sub>. Subsequent losses of CO and C<sub>3</sub>O are also observed. Theoretical calculations suggest mechanistic details for these losses.</p> </sec> <sec id="rcm6968-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>Loss of H<sub>2</sub> 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.</p> </sec> </abstract>