Fluorimetric determination of dopamine in pharmaceutical products and urine using ethylene diamine as the fluorigenic reagent Original Research Article

A sensitive and selective method for the determination of dopamine is described. Dopamine was oxidized by mercury(II) nitrate and the oxidation product was condensed with ethylene diamine to form a quinoxaline derivative which was strongly fluorescent. The measurement was carried out at 447 nm with excitation at 393 nm. Effects of pH, oxidants, and foreign ions on the determination of dopamine were examined. A linear relationship was obtained between the relative fluorescence intensity (RFI) and the concentration of dopamine in the range of 0.02 to 0.06 μg ml−1. The linear regression equation of the calibration graph is C=0.001347F−0.02564 (C is concentration of dopamine (μg ml−1) and F is relative fluorescence intensity in the equation), with a correlation coefficient of 0.9991 and a relative standard deviation of 4.4%. Dopamine was separated from adrenaline and noradrenaline in urine by thin layer chromatography. The detection limit is 18 ng ml−1, and the recovery is from 95.0 to 106.6%. This method can be used for the determination of dopamine in injection and urine samples.