Simultaneous Adsorptive Cathodic Stripping Voltammetric Determination of Nickel(II) and Cobalt(II) at an In Situ Bismuth‐Modified Gold Electrode

Abstract

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 BiAuE 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 ng L À1 for Ni(II) alone, whereas the LOD was 98 ng L À1 for Ni(II) and 58 ng L À1 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 BiAuE were in satisfactory agreement with the certified values and with those provided by complementary techniques, i.e., ICP-OES and ICP-MS.

Pyrolyzed Photoresist Carbon Electrodes for Trace Electroanalysis of Nickel(II)

“…The determination of Ni(II) at an in situ modified Bi-PPCE was carried out following a procedure previously described by Mardegan et al [34] for the determination of Ni at gold electrodes modified with a bismuth film. Briefly, the PPCE was dipped into a 0.1-mol•L −1 ammonium buffer solution containing 10 mg•L −1 Bi(III) in the form of its complex with tartrate and 1 × 10 −5 mol•L −1 dimethylglyoxime (DMG) as the complexing agent.…”

“…Following the procedure previously proposed for the determination of Ni at gold electrodes modified with a bismuth film [34], the study of the experimental conditions at PPC electrodes was carried out. Cyclic voltammetry was used to define the potential region for the deposition and dissolution of bismuth on PPCEs.…”

“…In the optimized procedure, the deposition of bismuth was fixed at a potential of −1.1 V, according to the literature [34]. In this step, Bi was deposited on the PPCE surface, whereas Ni(II)-(DMG)2 complex present in the solution was not adsorbed, since the adsorption occurs in the potential range of −0.8 and −0.6 V, while the reduction of the adsorbed complex is at ca.…”

“…In this step, Bi was deposited on the PPCE surface, whereas Ni(II)-(DMG)2 complex present in the solution was not adsorbed, since the adsorption occurs in the potential range of −0.8 and −0.6 V, while the reduction of the adsorbed complex is at ca. −0.95 V [34]. Figure 1B The effect of the bismuth concentration on the Ni(II) analysis was evaluated at a fixed deposition time of 60 s at the potential of −1.1 V, as suggested for the Bi deposition on gold electrodes [34].…”

“…Alves et al proposed a solid bismuth vibrating electrode for the determination of Ni(II) and Co(II) [33]. Recently, the use of an in situ prepared bismuth film electrode (BiFE) [29,34] and an antimony film electrode (SbFE) [35] for measuring Ni(II) and Co(II) ions was proposed, with the advantage of providing a simplified, faster and, yet, sensitive and reliable procedure together with a fresh electrode surface for each consecutive measurement.…”