Premium
A novel derivative for the assessment of urinary and salivary nitrate using gas chromatography/mass spectrometry
Author(s) -
Jackson Sarah J.,
Siervo Mario,
Persson Emma,
McKenna Louise M.,
Bluck Leslie J. C.
Publication year - 2008
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.3841
Subject(s) - chemistry , mesitylene , mass spectrometry , nitrate , gas chromatography , aqueous solution , trifluoroacetic anhydride , nitric acid , chromatography , nitration , trifluoroacetic acid , benzene , inorganic chemistry , organic chemistry
Abstract Previous gas chromatography/mass spectrometry (GC/MS) methods for determining nitrate in biological samples involve either hazardous chemicals or produce multiple isomers that can be difficult to quantitate. Modification of these methods, by the nitration of mesitylene instead of benzene and in the presence of trifluoroacetic anhydride rather than sulphuric acid, should enable simple isotopic quantitation for use in tracer studies, for example, in the measurement of nitric oxide production. Desiccated urine and saliva samples, in addition to aqueous labelled and unlabelled nitrate standards, were treated with trifluoroacetic anhydride and mesitylene at 70°C for 1 h, cooled, then sequentially washed with deionised water and aqueous sodium bicarbonate. The solution of nitromesitylene in mesitylene was separated, dried and analysed by GC/MS. The full mass spectra exhibited abundant ions at m/z 165 and 166 corresponding to the unlabelled and labelled molecular species of nitromesitylene, respectively. Selected ion monitoring of these masses for a series of gravimetrically prepared standards indicated good agreement with isotopic enrichments in the range 0.0625–5 mole % excess, and at nitrate concentrations within the physiological range of 0.078–2 mmol/L. Derivatised samples were stable with respect to isotopic enrichments and nitrate concentrations at −20°C for up to 21 days and exhibited excellent repeatability. Nitration of mesitylene proved to be a simple and rapid method for the measurement of isotope ratios in aqueous nitrates by GC/MS, which has applications in tracer studies and in concentration determinations by isotope dilution techniques for nitric oxide production. Copyright © 2008 John Wiley & Sons, Ltd.