Study on fluorescence property of dopamine and determination of dopamine by fluorimetry

The property of dopamine in acid–alkaline medium was studied by spectrofluorimetry and spectrophotometry. Effects of organic solvents on dopamine fluorescence spectra were examined and the reason was discussed. Among the organic solvents tested, methanol was selected as sensitizing reagent. A fluorescence quenching reaction took place in basic medium. Mechanism of fluorescence quenching was discussed. A simple, rapid and highly sensitive fluorimetric method for the determination of dopamine in injection and urine is developed. The measurement of relative fluorescence intensity was carried out at 315 nm with excitation at 279 nm. Effects of pH, foreign ions on the determination of dopamine have been examined. A linear relationship was obtained between the relative fluorescence intensity and concentration of dopamine in the range of 0.10–3.50 μg ml−1. The linear regression equation of the calibration graph is C=0.00447F−0.00748, with a correlation coefficient of linear regression of 0.9997 and relative standard deviation of 2.37%. The detection limit of this method is 0.082 μg ml−1, and recovery is from 104.2 to 106.6%. This method can be used for determination of dopamine in injection and urine sample. The results obtained by this method agreed with those by the official method (high performance liquid chromatography (HPLC)).