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Behavior of N-oxide derivatives in atmospheric pressure ionization mass spectrometry.
MedLine Citation:
PMID:  23413221     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
RATIONALE: Indolone-N-oxide derivatives possess interesting biological properties. The analysis of these compounds using mass spectrometry (MS) may lead to interference or under-estimation due to the tendency of the N-oxides to lose oxygen. All the previous works focused only on the temperature of the heated parts (vaporizer and ion-transfer tube) of the mass spectrometer without investigating other parameters. This work is extended to the investigation of other parameters.
METHODS: The behavior of N-oxides during atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) has been investigated using MS(n) ion trap mass spectrometry. Different parameters were investigated to clarify the factors implicated in the deoxygenation process. The investigated parameters were vaporizer temperature (APCI), ion-transfer tube temperature, solvent type, and the flow rates of the sheath gas, auxiliary gas, sweep gas and mobile phase.
RESULTS: The deoxygenation increased when the vaporizer temperature increased. The extent of the 'thermally' induced deoxygenation was inversely proportional to the ion-transfer tube temperature and auxiliary gas flow rate and in direct proportion to the mobile phase flow rate. Deoxygenation was not detected under MS/MS fragmentation and hence it is a non-collision-induced dissociation. N-Oxides have the tendency to form abundant 'non-classical' dimers under ESI, which fragment via dehydration rather than giving their corresponding monomer.
CONCLUSIONS: Deoxygenation is not solely a 'classical' thermal process but it is a thermal process that is solvent-mediated in the source. Deoxygenation was maximal with an APCI source while dimerization was predominant with an ESI source. Therefore, attention should be paid to these molecular changes in the mass spectrometer as well as to the choice of the ionization mode for N-oxides. Copyright © 2013 John Wiley & Sons, Ltd.
Authors:
Hany Ibrahim; François Couderc; Pierre Perio; Fabrice Collin; Françoise Nepveu
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Rapid communications in mass spectrometry : RCM     Volume:  27     ISSN:  1097-0231     ISO Abbreviation:  Rapid Commun. Mass Spectrom.     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-02-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8802365     Medline TA:  Rapid Commun Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  621-8     Citation Subset:  IM    
Copyright Information:
Copyright © 2013 John Wiley & Sons, Ltd.
Affiliation:
Université de Toulouse, UPS; UMR 152 (PHARMA-DEV), F-31062, Toulouse cedex 9, France; IRD, UMR 152, F-31062, Toulouse cedex 9, France.
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