Document Detail

Ozone-Induced Dissociation of Conjugated Lipids Reveals Significant Reaction Rate Enhancements and Characteristic Odd-Electron Product Ions.
MedLine Citation:
PMID:  23292977     Owner:  NLM     Status:  Publisher    
Ozone-induced dissociation (OzID) is an alternative ion activation method that relies on the gas phase ion-molecule reaction between a mass-selected target ion and ozone in an ion trap mass spectrometer. Herein, we evaluated the performance of OzID for both the structural elucidation and selective detection of conjugated carbon-carbon double bond motifs within lipids. The relative reactivity trends for [M + X](+) ions (where X = Li, Na, K) formed via electrospray ionization (ESI) of conjugated versus nonconjugated fatty acid methyl esters (FAMEs) were examined using two different OzID-enabled linear ion-trap mass spectrometers. Compared with nonconjugated analogues, FAMEs derived from conjugated linoleic acids were found to react up to 200 times faster and to yield characteristic radical cations. The significantly enhanced reactivity of conjugated isomers means that OzID product ions can be observed without invoking a reaction delay in the experimental sequence (i.e., trapping of ions in the presence of ozone is not required). This possibility has been exploited to undertake neutral-loss scans on a triple quadrupole mass spectrometer targeting characteristic OzID transitions. Such analyses reveal the presence of conjugated double bonds in lipids extracted from selected foodstuffs. Finally, by benchmarking of the absolute ozone concentration inside the ion trap, second order rate constants for the gas phase reactions between unsaturated organic ions and ozone were obtained. These results demonstrate a significant influence of the adducting metal on reaction rate constants in the fashion Li > Na > K.
Huong T Pham; Alan T Maccarone; J Larry Campbell; Todd W Mitchell; Stephen J Blanksby
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-1-5
Journal Detail:
Title:  Journal of the American Society for Mass Spectrometry     Volume:  -     ISSN:  1879-1123     ISO Abbreviation:  J. Am. Soc. Mass Spectrom.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-1-7     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9010412     Medline TA:  J Am Soc Mass Spectrom     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
School of Chemistry, University of Wollongong, Wollongong, NSW, Australia.
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