Electrochemical Behavior and Sensitive Determination of L-Tyrosine with a Gold Nanoparticles Modified Glassy Carbon Electrode

The electrocatalytic oxidation of L-tyrosine was investigated on a gold nanoparticles self-assembled glassy carbon electrode (gold nanoparticles/cysteamine/glassy carbon) using cyclic voltammetry and differential pulse voltammetry. Cyclic voltammetry was carried out to study the electrochemical oxidation mechanism of L-tyrosine, which showed an irreversible oxidation process at a potential of 0.681 V at a modified electrode and 0.807 V at a bare glassy carbon electrode. The anodic peak current linearly increased with the square root of the scan rate, suggesting that the oxidation of L-tyrosine at this kind of modified electrode is a diffusion-controlled process. A good linear relationship between the oxidation peak current and the L-tyrosine concentration in the range of 1.0 x 10(-7) to 3.0 x 10(-4) mol L(-1) was obtained in a phosphate buffer solution at pH 7.0. Good sensitivity, selectivity and stability of the modified electrode make it very suitable for L-tyrosine determination in a commercial amino acid oral solution.