Determination of mono-, poly- and hydroxy-carboxylic acid profiles of beverages as their 2-nitrophenylhydrazides by reversed-phase ion-pair chromatography

A simple, rapid and accurate method for the derivatization and quantitative reversed-phase ion-pair chromatographic analysis of mono-, poly- and hydroxy-carboxylic acids in wines, fruit juices, beer and Japanese ''sake'' is presented. Nine hydrazine derivatives were prepared in high yield by direct derivatization of the carboxylic acids with 2-nitrophenyl-hydrazine hydrochloride in sample matrix. Isocratic separation of the carboxylic acid hydrazides was performed within 18 min by a suitable combination of pH, the polarity of eluent and the size of the counter ion. The analytical results showed good recovery and reproducibility using 3-methylglutaric acid as an internal standard. Due to its superior selectivity and sensitivity, the present method can serve as a useful tool for routine analysis of carboxylic acids in foods and beverages.