Simultaneous kinetic determination of levodopa and carbidopa by H-point standard addition method

The kinetic H-point standard addition method (HPSAM) was applied to the simultaneous determination of levodopa and carbidopa. The method was based on the difference in the rate of oxidation of these compounds with Cu(II)–neocuproine system and formation of Cu(I)–neocuproine complex at pH 5.5. The absorbance of the Cu(I)–neocuproine complex was monitored at 453 nm. Experimental conditions such as pH, reagent concentrations, ionic strength and temperature were optimized. Simultaneous determination of levodopa and carbidopa was performed in the range of 0.8–4 and 0.2–1.5 μg ml−1, respectively. The proposed method was applied to the simultaneous determination of levodopa and carbidopa in pharmaceutical samples, and satisfactory results were obtained.