Highly selective square wave voltammetric determination of gallic acid in groundnut and tea samples using glycine(2-aminoethanoic acid) modified carbon paste electrode

Abstract

Phenolic compounds are well-known as antioxidants including many other important bioactive agents that have long been interested due to their benefits for human health, curing and preventing many diseases. Gallic acid (GA), is a naturally occurring most abundant phenolic acid compound found in groundnut, honey, mango, tea, wine, and various medicinal plants. Different techniques have been used for determination of GA. Electrochemical technique is of the best methods. A sensor with improved sensitivity for GA determination in real samples is developed. This work presents preparation of glycine modified carbon paste electrode (GMCPE) for square wave voltammetry determination of GA in groundnut and tea samples. Cyclic voltammetry and Electrochemical impedance spectroscopy results evidenced that modification of the surface of CPE by glycin improves the surface area and conductivity of the electrode. The appearance of an irreversible oxidative peak for GA with much reduced oxidative potential and about four folds current enhancement at GMCPE than the bare CPE showed the catalytic property of the modifier towards oxidation of GA. Under optimized conditions, SWV current response of GMCPE showed a linear dependence on the concentration of GA in the range 1.0 ​× ​10⁻⁶ – 2.0 ​× ​10⁻⁴ ​M, with LoD and LoQ 1.53 ​× ​10⁻⁸ ​M and 5.1 ​× ​10⁻⁸ ​M, respectively. Spike recovery results in groundnut and tea samples in the range 89.75–98.98% and 92.15–97.10%, respectively. Interference effect in the presence of selected potential interferents at their various levels with associated errors under 4.63% showed no interference on the current response of GA. The stability of the modifier with analysis time validated the applicability of the method for the determination of GA in real samples. Relative to previously reported works wider linear dynamic range, low LoD, high accuracy and selectivity make the present developed method an excellent candidate for determination of GA in real samples.