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Abstract
Cyclic voltammetry (CV) and square wave voltammetry (SWV) were used for characterizing and
determining Gallic acid concentration in groundnut. In this study, Gallic acid (GA) content in groundnut
was determined by SWV technique. The effect of Gallic acid concentration on the oxidation response of
Glycine modified carbon paste electrode (GMCPE) at pH of phosphate buffer solution were investigated
by CV. Application of the electrode is optimized with common cyclic voltammetry and square-wave
voltammetry system; the latter being recommended for quantification. The electrode is vigorous to
common interferents, and yield precise determinations in real samples analysis, even at very low gallic
acid concentrations. It was found that the anodic peak current of GA is directly related to the
concentration and scan rate, whereas during pH optimization, the anodic peak current was increased with
the pH value ranges 2 – 3. However, the peak current was found to decrease after pH 3.0. Hence, pH 3.0
is chosen as the optimum value for this work. On the other hand, the anodic peak potential is shifted to
less positive as a function of pH values used. A calibration curve was obtained by the square wave
voltammetry at GMCPE after square wave frequency, step potential, and square wave amplitude were
optimized. The optimized parameters chosen for the whole work were a wave frequency of 20 HZ, a step
potential of 6 mV, and wave amplitude of 25 mV, respectively. The limit of detection (LOD) and limit of
quantification (LOQ) of the GMCPE with specific results are 1.53 x 10-8 M and 5.1 x 10-8 M, respectively.
The recoveries ranging between 93.33 -99.42% were achieved indicating the method for the
determination of gallic acid in real samples was more valid.
Key words: Gallic acid; Square wave voltammetry; Groundnut; Modified electrode; Glycin |
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