Screen-printed electrodes modified with green-synthesized gold nanoparticles for the electrochemical determination of aminothiols

Commercially available gold screen-printed electrodes cured at high temperature were modified or functionalized at the surface with gold nanoparticles, mainly produced by a green synthesis method, and other carbon-based nanomaterials in order to enhance the electron transfer between the sulfhydryl groups of the aminothiols cysteine (Cys), methionine (Met), glutathione (GSH) and homocysteine (hCys) and the electrode. The electrochemical characterization by cyclic and differential pulse voltammetry of some of the modified electrodes showed an improved performance in terms of sensitivity, reproducibility, repeatability, linearity range and limits of detection (12, 1, 0.2 and 1 mu mol L-1 for Cys, Met, GSH, hCys, respectively) and quantification (40, 2, 0.5 and 2 mu mol L-1 for Cys, Met, GSH, hCys, respectively) as compared to unmodified units. Then, some of these modified devices were successfully applied to the determination of cysteine and methionine in dietary supplements by means of liquid chromatography with amperometric detection.