Simultaneous adsorptive cathodic stripping voltammetric determination of Nickel(II) and Cobalt(II) at the in-situ bismuth-modified gold electrode

A study on the simultaneous determination of Ni(II) and Co(II) dimethylglyoximates (Ni-DMG and Co-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified gold electrode (Bi-AuE) is reported. The key operational parameters, such as Bi(III) concentration, accumulation potential and accumulation time were optimized and the morphology of the Bi-microcrystals deposited on the Au-electrode was studied. The Bi- AuE allowed convenient analysis of trace concentrations of solely Ni(II) or of Ni(II) and Co(II) together, with cathodic stripping voltammograms characterized by well-separated stripping peaks. The calculated limit of detection (LOD) was 40 ngL1 for Ni(II) alone, whereas the LOD was 98 ngL1 for Ni(II) and 58 ngL1 for Co(II), when both metal ions were measured together. The optimized method was finally applied to the analysis of certified spring water (NIST1640a) and of natural water sampled in the Lagoon of Venice. The results obtained with the Bi- AuE were in satisfactory agreement with the certified values and with those provided by complementary techniques, i.e., ICP-OES and ICP-MS

Fabrication and Characterization of Carbon Nanotube-Hydroxyapatite Nanocomposite: Application to Anodic Stripping Voltammetric Determination of Cadmium

A novel chemically modified electrode for stripping determination of cadmium is presented in this paper. based on carbon nanotube-hydroxyapatite (CNT-HAP) nanocomposite, which can be prepared by an easy and effective one-step sonication. The newly synthesized nanocomposite was characterized with FTIR, TEM, and electrochemical methods. Due to the combination of the strong absorption ability of HAP and excellent electroanalytical properties of CNTs, the GC/CNT-HAP electrode has been successfully used for determination of Cd(2+) by anodic stripping voltammetry with a linear range of 20 nM -3 mu M. The sensitivity and detection limit are 25.6 mu A/mu M and 4 nM, respectively. The practical application of the proposed electrode has been carried out for the determination of trace levels of Cd(2+) in real water samples

Ex situ scanning electrochemical microscopy (SECM) investigation of bismuth/lead alloy film-modified gold electrodes in alkaline medium

Scanning electrochemical microscopy (SECM) in feedback mode was employed to characterise the reactivity and microscopic peculiarities of bismuth and bismuth/lead alloys plated onto gold disk substrates in 0.1 molL(-1) NaOH solutions. Methyl viologen was used as redox mediator, while a platinum microelectrode was employed as the SECM tip. The metal films were electrodeposited ex situ from NaOH solutions containing either bismuth ions only or both bismuth and lead ions. Approach curves and SECM images indicated that the metal films were conductive and locally reactive with oxygen to provide Bi(3+) and Pb(2+) ions. The occurrence of the latter chemical reactions was verified by local anodic stripping voltammetry (ASV) at the substrate solution interface by using a mercury-coated platinum SECM tip. The latter types of measurements allowed also verifying that lead was not uniformly distributed onto the bismuth film electrode substrate. These findings were confirmed by scanning electron microscopy images. The surface heterogeneity produced during the metal deposition process, however, did not affect the analytical performance of the bismuth coated gold electrode in anodic stripping voltammetry for the determination of lead in alkaline media, even in aerated aqueous solutions. Under the latter conditions, stripping peak currents proportional to lead concentration with a satisfactory reproducibility (within 5% RSD) were obtained