Rapid, sensitive and specific derivatization methods with 9-(hydroxymethyl)anthracene for the fluorimetric detection of carboxylic acids prior to reversed-phase high-performance liquid chromatographic separation

Three derivatization procedures are described for the pre-column fluorescence labelling of carboxylic acids. The methods are based on esterification with 9-(hydroxymethyl)anthracene. The carboxylic acid function is activated with 2-bromo-l-methylpyridinium iodide, N,N′-carbonyldiimidazole or N-ethyl-N′-(3-dimethylanopropyl)carbodiimide hydrochloride, respectively. Benzoic acid was completely converted into the corresponding ester with all three methods. About 100 fmol of the acid could be detected after high-performance liquid chromatographic analysis of the derivative. The methods are well suited for the analysis of carboxylic acids in plasma