3 research outputs found
Gas chromatography mass spectrometry (GC-MS) quantification of metabolites in stool using13 C labelled compounds
Β© 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 (26β25,626 ng/g), acetone (442β3006 ng/g), ethyl butanoate (39β2468 ng/g), ethyl 2-methylbutanoate (0.3β180 ng/g), dimethyl disulphide (35β1303 ng/g), 1-octen-3-one (12 ng/g), dimethyl trisulphide (10β410 ng/g), 1-octen-3-ol (0.4β58 ng/g), ethanoic acid (672β12,963 ng/g), butanoic acid (2493β11,553 ng/g), 3-methylbutanoic acid (64β8262 ng/g), pentanoic acid (88β21,886 ng/g), indole (290β5477 ng/g), and 3-methyl indole (37β3483 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 40β5312 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