Amperometric determination of heavy metal using an HRP inhibition biosensor based on ITO nanoparticles-ruthenium (III) hexamine trichloride composite: Central composite design optimization.

A novel horseradish peroxidase (HRP) enzyme inhibition biosensor based on indium tin oxide (ITO) nanoparticles, hexaammineruthenium (III) chloride (RUT), and chitosan (CH) modified glassy carbon electrode (GCE) was developed. The biosensor fabrication process was investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The amounts of ITO nanoparticles and RUT were optimized using a 22 central composite design for the optimization of electrode composition. The detection limits were determined as 8 nM, 3 nM, and 1 nM for Pb2+, Ni2+, and Cd2+, respectively. The inhibition calibration curves of the biosensor were found to be within the range of 0.009-0.301 µM with a sensitivity of 11.97 µA µM-1 cm-2 (0.85 µA µM-1) for Pb2+, 0.011-0.368 µM with a sensitivity of 10.84 µA µM-1 cm-2 (0.77 µA µM-1) for Ni2+, and 0.008-0.372 µM with a sensitivity of 10.99 µA µM-1 cm-2 (0.78 µA µM-1) for Cd2+. The type of HRP inhibition by Pb2+, Ni2+ and Cd2+ was investigated by the Dixon and Cornish-Bowden plots. The effects of possible interfering species on the biosensor response were examined. The analysis of Pb2+, Ni2+, and Cd2+ in tap water was demonstrated using the HRP/ITO-RUT-CH/GCE with satisfactory experimental results. The proposed method agreed with the atomic absorption spectrometry results.