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 fatty acid (SCFA) concentrations and their isotopic enrichments (M 0 + 1 and M 0 + 2) in human plasma. Sample preparation involves SCFA extraction and derivatization with 1‐( tert ‐butyldimethylsilyl)imidazole. Gas chromatography/mass spectrometry was performed using chemical ionization with ammonia as the reagent gas. Outstanding resolution, excellent linearity and good detection limits were obtained. Inter‐assay and intra‐assay repeatability was below 10% and 3% respectively for SCFA concentration. Inter‐assay repeatability was below 5%, 4%, 6%, and 14% for isotopic enrichment determination of [1‐ 13 C]acetate and [1,2‐ 13 C 2 ]acetate, [1‐ 13 C]propionate and [1‐ 13 C]butyrate respectively, with intra‐assay being below 6%. Such SCFA concentrations and isotopic enrichments were determined in the plasma of rats infused with a 13 C‐labeled SCFA. The turnovers of acetate, propionate and butyrate in rats were 19 µmol kg −1 min −1 , 2.6 µmol kg −1 min −1 , 0.3 µmol kg −1 min −1 respectively. Copyright © 2001 John Wiley & Sons, Ltd.