Acetate, propionate and butyrate in plasma: determination of the concentration and isotopic enrichment by gas chromatography/mass spectrometry with positive chemical ionization

This study describes a rapid and simple method to determine short-chain fat ty acid (SCFA) concentrations and their isotopic enrichments (M-0+1 and M-0 +2) in human plasma. Sample preparation involves SCFA extraction and deriva tization with 1-(tert-butyldimethylsilyl)imidazole. Gas chromatography/mass spectrometry was performed using chemical ionization with ammonia as the r eagent gas. Outstanding resolution, excellent linearity and good detection limits were obtained. Inter-assay and intra-assay repeatability was below 1 0% and 3% respectively for SCFA concentration. Inter-assay repeatability wa s below 5%, 4%, 6%, and 14% for isotopic enrichment determination of [1-C-1 3]acetate and [1,2-1-C-12(2)]acetate, [1-C-13]propionate and [1-C-13]butyra te respectively, with intra-assay being below 6%. Such SCFA concentrations and isotopic enrichments were determined in the plasma of rats infused with a C-13-labeled SCFA. The turnovers of acetate, propionate and butyrate in rats were 19 mu mol kg(-1) min(-1), 2.6 pmol kg(-1) min(-1), 0.3 mu mol kg( -1) min(-1) respectively. Copyright (C) 2001 John Wiley & Sons, Ltd.