Abstract:
Anodic stripping voltammetric determination of ascorbic acid using carbon paste electrode
modified with anthraquinone is investigated in the present work. Electrochemical
investigation of ascorbic acid using square wave voltammetry using the carbon paste
electrode modified with anthraquinone was found to be very sensitive. Compared with the
unmodified carbon paste electrode, the striping anthraquinone modified electrode remarkably
increases the peak currents of ascorbic acid, and showed excellent catalytic activity for the
oxidation of ascorbic acid. Cabbages cultivated from three different areas (Guld, Karishewa
and Birbira) were used for investigation. Voltammetry responses of cabbage extracts of the
two samples showed the presence of ascorbic acid whereas they can’t see the presence of
ascorbic acid in one of the samples collected from Birbira. Optimization of different variables
such as pH of working solution, scan rate and square wave parameters such as frequency,
amplitude and step potential were made to improve the method efficiency during the
experiment. It was found that the anodic peak current of AA is directly related to concentration and
scan rate whereas the peak current increases up to pH 4 and decreases beyond pH 4.SWV was
used to plot the calibration curve and a good linear relationship between anodic peak current
and ascorbic acid concentration in the range 5x10
-5
to 4x10
-3
M, with the correlation
coefficient to 0.99931. The application of the modified electrode for the determination of
ascorbic acid in food formulation showed good recovery with reproducible results 86.5%.
Keywords: stripping voltammetry, cyclic voltammetry, Square Wave Voltammetry,
Anthraquinone, Modified Carbon Paste Electrode, Ascorbic acid