Determination of Short-Chain Fatty Acids in Stool Ultrafiltrate and Urine

A new method is reported for determining total shortchain fatty acids in stool water and urine. The method uses ion-exchange resins to remove interfering substances, and determines these acids by direct titration. Lactic acid, if present, is determined along with the short-chain (C1-C6) organic acids. Interferences such as carbonate, phosphate, creatinine, bile acids, and uric acid are removed by the ion-exchange treatment. Values obtained by this simplified technique correlate very well with those by gas-chromatographic analyses of the same sample, and the method represents a significant improvement over the Van Slyke technique.