Spectrophotometric Determination of Dopamine in Bulk and Dosage Forms Using 2,4-Dinitrophenylhydrazine

Dopamine (DA) hydrochloride is a sympathomimetic agent used therapeutically for the correction of hemodynamic disorders associated with shock episodes. Although several analytical methods have been described, a spectroscopic assay of DA after chemical derivatization with 2,4-dinitrophenylhydrazine (DNP) is still unexamined. Therefore, the optimization of the reaction parameters and validation of developed method were required.

The method is based on coupling of DA as a phenolic compound with a diazonium salt to produce an intensely colored azo derivative. DNP was oxidized with potassium periodate to produce a diazonium salt that coupled with DA in basic media. The experimental parameters were then optimized. The developed method was validated according to International Conference on Harmonisation Guidelines and was applied to dosage forms. The results were compared with the data of a reference method.

The method was linear in a concentration range between 5 and 50 μg/mL. The regression line equation was Y=0.042±0.0003X+0.0672±0.0015 with a regression coefficient of 0.9944 (n=5). The limit of detection and limit of quantification were 0.32 and 0.97 μg/mL, respectively. The precision was satisfactory; the percentage relative standard deviation did not exceed 2%. The average values of the recovery study were in the range 98.90- 100.40±0.31-1.21%. The developed method was applied successfully for the determination of DA in injection and infusion fluid.

The method is accurate, sensitive, and practical for DA analysis in quality control laboratories.