Fluorometric Determination of 3,4-Dihydroxyphenylalanine with 2-Cyanoacetamide

A new method has been developed for the fluorometric determination of 3,4-dihydroxyphenylalanine on the basis of the reaction with 2-cyanoacetamide. The reaction product has excitation and emission peaks at 335 and 405 nm, respectively. Under the optimum conditions, the fluorescence intensity is a linear function of 3,4-dihydroxyphenylalanine concentration between 2.5 × 10−8 and 2.0 × 10−6 mol/L. The detection limit, corresponding to a signal-to-noise ratio of 3, is 6.8 × 10−9 mol/L. Most amino acids, epinephrine, and norepinephrine do not interfere with the determination of 3,4-dihydroxyphenylalanine. The proposed method has been successfully applied to the determination of 3,4-dihydroxyphenylalanine in pharmaceutical preparations.