Electrochemical Behaviour of the Antioxidant Gallic Acid Using a Low-Cost Screen-Printed Carbon Sensor and Its Exploitation for Banana Wine Analysis

A low-cost screen-printed carbon electrode (SPCE) was used to determine gallic acid (GA) in banana wine (BW). Cyclic voltammetry (CV) showed GA oxidation in Phosphate-Buffered Saline (PBS, pH 7.0) with 10% ethanol was diffusion-controlled, forming a quinone species. This supporting electrolyte was applied for calibration using the identified CV and differential-pulsed voltammetry (DPV) peaks, whose low potentials ensured good selectivity and stability. Linearity was obtained between 0.25–5.00 μM GA, suitable for BW analysis. BW was filtered, diluted (1:20) in electrolyte, and analysed via the standard addition method. GA concentrations were 7.369 μM (CV) and 7.570 μM (DPV), with no significant differences. Further validation of the voltammetric procedure using fortified BW confirmed its reliability, with excellent recoveries of 94.41% (CV) and 99.33% (DPV). The SPCE-based voltammetric approach offers a simple, accurate, and low-cost method for GA determination in BW, combining good sensitivity, selectivity, and reproducibility.