A new electrochemical sensor for simultaneous determination of arbutin and vitamin C based on hydroxyapatite-ZnO-Pd nanoparticles modified carbon paste electrode.

A highly sensitive and selective sensor was fabricated based on Hydroxyapatite-ZnO-Pd NPs modified carbon paste electrode (HAP- ZnO-Pd NPs/CPE) for simultaneous determination of Arbutin (AT) and vitamin C (VC) for the first time. Characterization was performed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The modified electrode was studied by different methods including electrochemical impedance spectroscopy and cyclic voltammetry. The HAP- ZnO-Pd NPs/CPE exhibited excellent electrocatalytic activity towards the oxidations of AT and VC in phosphate buffer solution (pH 7.0) and the corresponding electrochemical signals have appeared as two well resolved oxidation peaks with significant peak potential differences of 0.23 V. Kinetic parameters such as charge transfer coefficient (0.52 and 0.44 for AT and VC respectively), standard heterogeneous electron transfer rate constant (0.336 s-1 and 0.590 s-1 for AT and VC respectively), and other electrochemical parameters were calculated via voltammetry techniques. Differential pulse voltammetry was used for simultaneous determination of AT and VC using the HAP- ZnO-Pd NPs/CPE electrode. At the optimum conditions, for simultaneous determination by synchronous change of the analyte concentrations, the linear response ranges were between 0.12-56 μM for AT and 0.12-55.36 μM for VC with detection limits of 85.7 and 19.4 nM respectively while sensitivity of proposed sensor for AT and VC was 0.98 μA/μM and 0.94 μA/μM. Reproducibility (intra-; 1.16% and 1.16% for AT and VC respectively and inter-electrode reproducibility of 2.03% and 3.28 for AT and VC respectively), and response time about 3.5 min were obtained. Furthermore, HAP- ZnO-Pd NPs/CPE was successfully applied for the independent determination of VC in fruit juice as well as the simultaneous determination of AT and VC in lightening cream samples.