Abstract:
In this work, an electrochemical method for the determination of ascorbic acid using
anthraquinone modified carbon paste electrode was developed. The electrode modification has
been performed by mixing varying amounts modifier (anthraquinone), carbon paste and the
solvent (paraffin oil) for homogenization. Under the optimized conditions. Anthraquinone
modified electrode increased the peak currents of ascorbic acid, and greatly lowers the peak
potential separation, compared to unmodified counterpart. Optimization of different variables
such as pH of the working solution, scan rate, modifier composition and cyclic voltammetry
parameters were made to improve the efficiency of the method. Moreover, the data
reproducibility and electrode stability and recovery for the analysis were evaluated. The
developed method was used for electroanalysis of ascorbic acid from pharmaceutical samples
collected from Pharmacies at Jimma town. The peak potential shift with pH in the range 3.0 to
8.0, indicating participation of protons during the oxidation of ascorbic acid. Under optimized
conditions and cyclic voltammetric parameters, an excellent linear dependence of the oxidative
peak current on concentration of ascorbic acid was observed in the range 5×10-6
- 1×10-4 M with
limits of detection (LOD) and quantification (LOQ) of 1.63 and 5.44 μM, respectively.
Percentage recovery results being 98.5% for spiked standard ascorbic acid in pharmaceutical
tablets. This method confirmed the potential applicability on the determination of ascorbic acid
in real samples
