Determination of volatile and non-volatile organic acids in technical sugar solutions by ion-exclusion chromatography

Abstract

Volatile and non-volatile organic acids present in sugar process juices were separated by ion-exclusion chromatography on an HPICE-AS1 cation-exchange column (H + form) using both dilute hydrochloric acid and 2-propanol-water solutions of tridecafluoroheptanoic acid. Coupled with an anion-exchange micromembrane suppressor, a conductivity detector made it possible to reveal citric, tartaric, gluconic, malic, lactic, succinic, glycolic, formic, acetic and pyrrolidonecarboxylic acid in the presence of inorganic acids and non-ionic organic matter. In sugar process juices subjected to alkaline and/or oxidative treatment, increasing concentrations of the major acid components, i.e., acetic, formic and lactic acid, can be measured. The analysis is performed in the presence of sucrose and a simple clean-up by rapid batch treatment with a cation exchanger (H + form) is sufficient to remove proteins and cations. The multiple standard addition procedure is used for calibration.