Separation and determination of low-molecular-weight straight-chain (C1C8) carboxylic acids by gas chromatograpy of their anilide derivatives

Abstract The analysis for formic, acetic, propionic, n -butyric, n -valeric, n -hexoic, n -heptoic and n -octoic acids in acqueous and non-aqueous mixtures by the gas chromatography of their anilide derivatives on sodium dodecylbenzenesulphonate coated on Chromosorb G is described. The derivatives of C 2 C 8 acids are formed in non-aqueous conditions via thionyl chloride treatment while the formic acid derivative is formed in aqueous conditions after pH adjustment. Optimum conditions for quantitative derivative formation are discussed. Variations of the p K a values of the acids with derivative retention times and retention times and response factors with the number of carbon atoms are illustrated.