Graphene oxide coated with sol–gel was prepared by a one-pot synthesis from phenyltriethoxysilane and tetramethoxysilane. The electrochemical behavior of tryptophan on the graphene/silicon oxide modified electrode was evaluated by differential pulse voltammetry (DPV). The oxidation peak current of tryptophan in phosphate buffer solution (pH = 7.0) at the modified electrode was linear in the range of 5.0 × 10−5 to 2.0 × 10−4 mol L−1 (r2 = 0.998) and 5.0 × 10−7 to 5.0 × 10−5 mol L−1 (r2 = 0.985) with a detection limit of 4.95 × 10−7 mol L−1 (S/N = 3). The modified electrodes showed good stability and reproducibility. The interference of glucose, ascorbic acid, tyrosine, glycine and cysteine was also studied.
