Development and validation of a reversed-phase liquid chromatography method for the quantitative determination of carboxylic acids in industrial reaction mixtures

Usually analysis of low molecular-mass carboxylic acids was performed by anion-exchange or ion-exclusion chromatographic methods. Reversed-phase liquid chromatography (RPLC) was evaluated in this work as an alternative method for the analysis of low molecular-mass aliphatic mono- and di-carboxylic acids (formic, acetic, propionic, butyric, valeric, caproic, succinic, glutaric and adipic) in aqueous media. The separation of the nine organic acids was optimised in 21 min on a high-density C18 column with an elution gradient made up of HClO4 aqueous solution 10−3 mol L−1 and acetonitrile. For the quantitation, external standard and standard addition methods were compared. Both methods gave similar results, so the most convenient method, external standard, was chosen for acids quantitation. Then the method had been validated and applied to the semi-quantitative analysis of formic and acetic acids and to the quantitative analysis of the others compounds in industrial reaction mixtures with concentrations ranging from 20 to 570 ppm.