The quantitative extraction and gas-liquid chromatographic determination of organic acids in urine

Abstract

A method for the quantitative extraction and gas-liquid chromatographic determination of organic acids in aqueous solution and biological fluids has been developed. The acids are extracted by a DEAE-Sephadex anion-exchange column, neutral and basic compounds are removed by washing with water and the acids are eluted with a pyridinium acetate buffer. The ethoximes of oxo-acids are formed in the eluate to stabilise these compounds and the eluate is then freeze-dried under carefully controlled conditions. The residue of dry free acids and their pyridinium salts is trimethylsilylated and the trimethylsilyl derivatives are separated and quantitatively determined by gas-liquid chromatography with the use of internal standards. The method would not be suitable for the determination of formic, acetic, propionic or butyric acid because of their volatility.

The accuracy and precision of the method, which can be applied to other protein-free biological fluids as well as urine, are discussed.