Simultaneous measurement of plasma concentrations and 13C-enrichment of short-chain fatty acids, lactic acid and ketone bodies by gas chromatography coupled to mass spectrometry

A new method has been developed for the simultaneous measurement, in a reduced plasma sample, of concentration and C-13-isotopic enrichment of acetic, propionic, butyric, lactic, acetoacetic and beta-hydroxybutyric acids by gas chromatography coupled to mass spectrometry. After plasma deproteinisation, a diethylic extraction and a N-tert.-butyldimethylsilyl-N-methyltrifluoroacetamide derivatisation were performed. Both diethyl extraction and derivatisation procedures were optimised using the central composite designs methodology. The optimised method provides good linearity, intra-day and within-day repeatability. Except for beta-hydroxybutyric (49 muM) and acetoacetic acid (5 muM), detection limits were ranging between 0.2 and 0.7 muM allowing uses of this method for colonic metabolism studies. (C) 2002 Elsevier Science B.V. All rights reserved.