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Use of diagnostic neutral losses for structural information on unknown aromatic metabolites: an experimental and theoretical study
Author(s) -
Bourcier Sophie,
Hoppilliard Yannik
Publication year - 2009
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.3852
Subject(s) - chemistry , protonation , ketene , fragmentation (computing) , density functional theory , dissociation (chemistry) , molecule , collision induced dissociation , computational chemistry , mass spectrum , hydrogen atom , ion , side chain , structural isomer , functional group , stereochemistry , tandem mass spectrometry , mass spectrometry , medicinal chemistry , organic chemistry , group (periodic table) , chromatography , polymer , computer science , operating system
This work presents the use of neutral losses (NL) for the identification of compounds related to the metabolism of tyrosine. The mass spectra of all the studied compounds, recorded at several collision energies, are compared. The fragmentation mechanism of protonated molecules, MH + , is explained by combining collision‐induced dissociation (CID) mass spectra and density functional theory (DFT) calculations. The results show that the first fragmentation is the elimination from MH + of a neutral molecule including a functional group of the linear chain. Three primary neutral losses are observed: 17 u (NH 3 ), 18 u (H 2 O) and 46 u (H 2 O+CO) characterizing amino, hydroxyl and carboxylic functions on the linear chain. The presence and abundance of ions corresponding to these losses are dependent on (i) the position of the functional group on the linear chain, (ii) the initial localisation of the protonating hydrogen, and (iii) the substitution of the aromatic ring. For compounds including a functional group on the benzylic carbon atom, the investigation of the other functions requires the knowledge of secondary fragmentations. Among these secondary fragmentations we have retained the loss of NH 3 from [MH–18u] + and the loss of ketene from [MH–17u] + . Experimentally these fragmentations are detected using losses of 35 u and 59/73 u. In other words, NL35 identifies hydroxy and amino compounds and NL 46 and/or NL59/73 identify carboxylic acids. The search for characteristic neutral losses is used for the analysis of compounds in a mixture and the analysis of biological fluid. We show that selective search of several neutral losses allows also the unambiguous differentiation of isomers and gives the opportunity to identify compounds in biological fluids. Copyright © 2008 John Wiley & Sons, Ltd.