Sensitive Determination of Dopamine by Its Fluorescence Enhancement on Terbium(III)-Dipicolinic Acid System

Biologically important compound dopamine plays an important role in the central and peripheral nervous systems. Insufficient dopamine level due to the loss of dopamine cells may lead to disease called schizophrenia and Parkinson's disease. An enhanced fluorimetric determination of dopamine is achieved using fluorescence of terbium complex, Tb³⁺–DPA, where DPA is dipicolinic acid. Under the optimum conditions, the method showed good stability and reproducibility. The application of this method for the determination of dopamine was found to be satisfactory. Linear response was found in the range of 5 × 10⁻⁸ M–2 × 10⁻⁶ M with a detection limit of 1.2 × 10⁻⁸ M. Recovery of the target compounds was obtained more than 98% with good quality parameters: linearity (r ² > 0.997), limit of detection (LOD) and limit of quantification (LOQ) values 1.2 × 10⁻⁸ M and 4.1 × 10⁻⁸ M, respectively, and run-to-run and day-to-day precisions (from 10 independent measurements for 1.0 × 10⁻⁶ M of dopamine) with relative standard deviation (RSD) 3.33%. The content of the analyzed samples was found 198.4 mg which are very close to the label claimed by the manufacturer (200 mg) in dopaminum hydrochloricum tablets. To the best of our knowledge, such kind of work has been carried out for the first time which offers very good results. Therefore, this method can be proposed for routine analysis of these compounds in tablets.