Study on the Electrochemical Properties of Kojic Acid at a Poly(glutamic Acid)-Modified Glassy Carbon Electrode and Its Analytical Application

A poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) for the electrochemical determination of kojic acid was developed. The polymerization mechanism of glutamic acid at the glassy carbon electrode, the electrocatalytic mechanism of the poly(glutamic acid) film toward kojic acid, and the electrochemical behavior of kojic acid at the PGA/GCE were investigated. The studies revealed that the oxidation of kojic acid at the PGA/GCE is greatly facilitated, which is attributed to the weakening of the bond energy between oxygen and hydrogen due to the formation of hydrogen bond between hydroxyl group in kojic acid and the nitrogen atom in poly(glutamic acid). The oxidation of kojic acid at the PGA/GCE is a one proton–one electron process. The catalytic effect was further used to determine kojic acid by cyclic voltammetry. The oxidation peak current shows a linear relationship with the concentrations of kojic acid in the range of 8.00 × 10 −6 to 6.60 × 10 −4  mol L −1 with the detection limit of 8.00 × 10 −7  mol L −1 . The modified electrode shows excellent sensitivity, selectivity, and stability and has been applied to detect kojic acid in a variety of food products with satisfactory results.