Montmorillonite clay-modified disposable ink-jet-printed graphene electrode as a sensitive voltammetric sensor for the determination of cadmium(II) and lead(II)

This work describes a new sensitive sensor for the simultaneous electrochemical determination by square wave anodic stripping voltammetry of Cd2+ and Pb2+ ions in aqueous solution, based on a disposable ink-jet-printed graphene electrode (IPGE) modified by a thin film of montmorillonite (Mont) clay mineral. The clay was characterized by X-ray diffraction and scanning electron microscopy while the Mont–IPGE was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry before its exploitation for sensing studies. EIS results revealed a low electron transfer rate on Mont–IPGE during the electro-oxidation of [Fe(CN)6]3−. The stripping response on both Cd2+ and Pb2+ analytes was improved by the in situ co-deposition with bismuth, added to the electrolyte solution, on the clay substrate. The proposed electrode showed great stability and good reproducibility. The key experimental parameters governing the stripping analysis of Cd2+ and Pb2+ were optimized. A linear relationship between peak currents and concentrations of the analytes was obtained in the range from 0.01 to 0.21 µM, leading to detection limits of 0.42 nM for Cd2+and 1.14 nM for Pb2+ ions, respectively (S/N = 3). The sensitivities to Cd2+ and Pb2+ ions were 921.8 A cm−2 M−1 and 1960.8 A cm−2 M−1, respectively. The Mont–IPGE sensor was used for the quantification of lead and cadmium in a mineral water.