Selective voltammetric determination of gallic acid in citrus juices using a carminic acid-modified platinum electrode

A hyperactive platinum electrode was modified with a carminic acid (CA) film to enhance its selectivity toward gallic acid (GA) in an ascorbic acid (AA)–rich environment. The K₃[Fe(CN)₆] test, along with chronoamperometry, confirmed the catalytic activity of the modified electrode for GA analysis. SEM-EDX characterization further verified the successful deposition of CA on the platinum surface. The oxidation peak potential of GA was observed at approximately 0.45 V. Modification with CA enhanced the GA oxidation current by 20.8 %, increasing it from 1.425 mA to 1.722 mA. The oxidation peak currents obtained from differential pulse voltammograms exhibited a linear relationship with GA concentrations ranging from 1.25 × 10⁻³ mM to 0.5 mM. Based on a signal-to-noise ratio of 3, the detection limit was calculated to be 0.32 µM. The proposed CA-modified sensor was successfully applied to quantify GA in fresh orange and lemon juice samples, without significant interference from AA or citric acid (CA). The electrode demonstrated accurate GA determination in citrus juices, with recoveries ranging from 89.96 % to 102.65 %, confirming its practical applicability in food analysis.