Fluorometric determination of sialic acids using malononitrile in weakly alkaline media and its application to postcolumn labeling in high-performance liquid chromatography.

A sensitive method for determination of sialic acids by monitoring the fluorescence produced with malononitrile in borate buffer has been established. Measurement of the fluorescence intensity of the reaction mixture at 430 nm with irradiation at 360 nm allowed determination of 3-60 nmol of sialic acids with high reproducibility. A few amino sugars and deoxy sugars, as well as catecholamines reacted with this reagent; however other carbohydrates, amino acids, amines, aldehydes, and carboxylic acids including alpha-keto acids, etc., showed little reactivity. This method was successfully applied to postcolumn fluorescence labeling of sialic acids in high-performance liquid chromatography.