Capillary electrophoresis for short chain organic acids in faeces: Reference values in a Mediterranean elderly population

There is increasing evidence that gut microflora and fermentation processes in the large intestine are important for health, and that health-promoting effects are mediated by fermentation products. Usually analytical methods for these compounds are tedious. A simple and rapid procedure of aqueous extraction from the stools has been optimized. After extraction, an aliquot of the aqueous layer was directly injected into the capillary electrophoresis equipment. Oxalic, formic, fumaric, 2-ketoglutaric, succinic, citric, acetic, propionic, 2-ketoisovaleryc, butyric, isovaleric lactic, glyceric 2-hydroxybutyric, and valeric acids were separated and identified. Electrophoretic conditions were: phosphate buffer 234 mM pH 6.10 with 12% (v/v) methanol with a coated capillary at −10 kV of applied potential. The method was validated for a representative group of compounds: acetic, propionic butyric, 2-hydroxybutiric, isovaleric, and oxalic acids, including the comparison of results with ionic chromatography. Finally 136 samples from healthy humans aged 60–80, both male and female living in Spain, were measured. They could be used as reference values for further studies.