First Report for Determination of d-Penicillamine in the Presence of Tryptophan Using a 2-Chlorobenzoyl Ferrocene/Ag-Supported ZnO Nanoplate-Modified Carbon Paste Electrode.

In this work, a carbon paste electrode modified with Ag-ZnO nanoplates and 2-chlorobenzoyl ferrocene was prepared and applied for the determination of d-penicillamine in the presence of tryptophan. The morphologies of Ag-ZnO nanoplates were examined by scanning electron microscopy. It was found that under an optimum condition (pH 7.0), the oxidation of d-penicillamine at the surface of such an electrode occurs at a potential about 165 mV less positive than that of an unmodified carbon paste electrode. The diffusion coefficient (D = 7.6 × 10-6 cm2/s) and the electron transfer coefficient (α = 0.54) for d-penicillamine oxidation were also determined. The proposed method exhibited a wide linear dynamic range of 0.03-250.0 µM, with an LOD (S/N = 3) of 0.015 µM. Moreover, the modified electrode exhibited good reproducibility and high selectivity, demonstrating its feasibility for the analytical purpose. Lastly, this new sensor was used for the determination of d-penicillamine and tryptophan in real samples.