Electrochemical Sensor for Detection of Gallic Acid Based on Carmine Modified Platinum Electrode: Application in Estimation of Total Polyphenols in Onion Powder Samples

Abstract

A hyperactive platinum electrode modified with a carmine film was employed for the determination of gallic acid(GA) in onion powder, effectively differentiating GA in the presence of a low concentration of ascorbic acid. The catalytic performance of this modified electrode for gallic acid analysis was validated using the Fe(CN)63- test. The oxidation potential of GA was identified at approximately 0.45V vs. Ag/AgCl electrode utilizing cyclic voltammetry (CV). Differential pulse voltammograms (DPVs) exhibited a linear correlation between the oxidation peak currents and GA concentrations ranging from 1.25 µM to 1.0 mM. The detection limit, based on a signal-to-noise ratio of 3, was determined to be 0.3 µM. This modified sensor was subsequently applied for quantifying GA in tap water and onion powder, showing no significant interference from ellagic acid, caffeic acid, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, NO₃⁻, SO₄²⁻, and Cl⁻. Although ascorbic acid, which exhibited minimal response to the modified electrode, reduced the GA oxidation current by approximately 13% when spiked at the same concentration. Recovery rates were found to be 102.76–105.45% for tap water and 97.52–104.67% for onion powder, demonstrating the sensor's robustness and