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Gas chromatography mass spectrometry (GC-MS) quantification of metabolites in stool using13 C labelled compounds

Gould, Oliver; Costello, Ben de Lacy; Smart, Amy; Jones, Peter; Macmaster, Angus; Ransley, Karen; Ratcliffe, Norman

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Authors

Amy Smart

Peter Jones

Angus Macmaster

Karen Ransley

Norman Ratcliffe Norman.Ratcliffe@uwe.ac.uk
Professor in Materials & Sensors Science



Abstract

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. It has become increasingly important to qualitatively and quantitatively assess the volatile metabolites in a range of bodily fluids for use in monitoring health. There has been relatively little work on the quantitative analysis of compounds, particularly with respect to the effects of ethnicity or geographic location. A novel method for the quantification of compounds in stool using13 C labelled compounds as internal standards is presented. Using thermal desorption gas chromatography mass spectrometry, stool samples from 38 healthy volunteers were analysed. The13 C labelled compounds, acetone, ethyl butanoate, ethanoic acid, butanoic acid, 3-methylbutanoic acid, and indole, were added as internal standards. This process mimics the solubility characteristics of the compounds and thus the method was able to quantify the compounds within the solid stool. In total, 15 compounds were quantified: Dimethyl sulphide (26–25,626 ng/g), acetone (442–3006 ng/g), ethyl butanoate (39–2468 ng/g), ethyl 2-methylbutanoate (0.3–180 ng/g), dimethyl disulphide (35–1303 ng/g), 1-octen-3-one (12 ng/g), dimethyl trisulphide (10–410 ng/g), 1-octen-3-ol (0.4–58 ng/g), ethanoic acid (672–12,963 ng/g), butanoic acid (2493–11,553 ng/g), 3-methylbutanoic acid (64–8262 ng/g), pentanoic acid (88–21,886 ng/g), indole (290–5477 ng/g), and 3-methyl indole (37–3483 ng/g). Moreover, by altering the pH of the stool to pH 13 in conjunction with the addition of13 C trimethylamine, the method was successful in detecting and quantifying trimethylamine for the first time in stool samples (range 40–5312 ng/g). Statistical analysis revealed that samples from U.K. origin had five significantly different compounds (ethyl butanoate, 1-octen-3-ol, ethanoic acid, butanoic acid, pentanoic acid, and indole) from those of South American origin. However, there were no significant differences between vegetarian and omnivore samples. These findings are supported by pre-existing literature evidence. Moreover, we have tentatively identified 12 compounds previously not reported as having been found in stool.

Journal Article Type Article
Acceptance Date Oct 19, 2018
Publication Date Dec 1, 2018
Deposit Date Nov 23, 2018
Publicly Available Date Nov 23, 2018
Journal Metabolites
Electronic ISSN 2218-1989
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 8
Issue 4
Pages 75
DOI https://doi.org/10.3390/metabo8040075
Keywords carbon isotopes, gas-chromatography mass-spectrometry, quantification, stool, volatile compounds
Public URL https://uwe-repository.worktribe.com/output/857899
Publisher URL http://dx.doi.org/10.3390/metabo8040075
Contract Date Nov 23, 2018