Complexation-Based Detection of Nickel(II) at a Graphene-Chelate Probe in the Presence of Cobalt and Zinc by Adsorptive Stripping Voltammetry

Abstract

The adsorptive stripping voltammetric detection of nickel and cobalt in water samples at metal film electrodes has been extensively studied. In this work, a novel, environmentally friendly, metal-free electrochemical probe was constructed for the ultra-trace determination of Ni2+ in water samples by Adsorptive Cathodic Stripping Voltammetry (AdCSV). The electrochemical platform is based on the adsorptive accumulation of Ni2+ ions directly onto a glassy carbon electrode (GCE) modified with dimethylglyoxime (DMG) as chelating agent and a Nafion-graphene (NGr) nanocomposite to enhance electrode sensitivity. The nafion-graphene dimethylglyoxime modified glassy carbon electrode (NGr-DMG-GCE) shows superior detection capabilities as a result of the improved surface-area-to-volume ratio and enhanced electron transfer kinetics following the incorporation of single layer graphene, while limiting the toxic effects of the sensor by removal of the more common mercury, bismuth and lead films. Furthermore, for the first time the NGr-DMG-GCE, in the presence of common interfering metal ions of Co2+ and Zn2+ demonstrates good selectivity and preferential binding towards the detection of Ni2+ in water samples. Structural and morphological characterisation of the synthesised single layer graphene sheets was conducted by Raman spectrometry, HRTEM and HRSEM analysis. The instrumental parameters associated with the electrochemical response, including accumulation potential and accumulation time were investigated and optimised in addition to the influence of DMG and graphene concentrations. The NGr-DMG-GCE demonstrated well resolved, reproducible peaks, with RSD (%) below 5% and a detection limit of 1.5 µg L−1 for Ni2+ reduction at an accumulation time of 120 s. The prepared electrochemical sensor exhibited good detection and quantitation towards Ni2+ detection in tap water samples, well below 0.1 mg L−1 set by the WHO and EPA standards. This is comparable to the South African drinking water guidelines of 0.15 mg L−1.

A sensitive, selective and rapid determination of lead(II) ions in real-life samples using an electrochemically reduced graphene oxide-graphite reinforced carbon electrode

“…4a). In previous paper, HB grade of GRC was used as an electrode substrate material for the determination of Pb(II) ions using bismuth [27] and a mixture of graphene and bismuth [24]. Tavares and Barbeira [26], observed that the harder graphite pencils (acronym H) are more useful for the electrochemical purposes, due to their smaller reduction/oxidation peak-to-peak separation (⧍E p ) and reduction/ oxidation peak current ratio (ipc/ipa) ∼1.…”

“…Many graphene based sensors utilise glassy carbon as an electrode substrate material [10,24]. Conversely, glassy carbon is typically expensive, require routine polishing, and has limited lifespan [25].…”

“…The main attraction of this material is its high electrical conductivity, fast and easy pre-treatment, low cost, wide availability, and low background current [27]. GRC (hardness-blackness (HB) grade) has been used as an electrode substrate material for the determination of trace metals using bismuth [27] and mixture of graphene and bismuth [24]; however, there is no detailed report on the influence of different GRC grade with modifiers for the determination of Pb (II) ions.…”

Highly Selective and Sensitive Electrochemical Determination of Ni(II) in Real Samples Based on Ion‐imprinted Polymer Technology

“…Various methods including spectrometry [5][6][7][8][9][10][11][12][13][14][15][16], liquid chromatography [17,18], ion chromatography [19], flame photometry [20] and electrochemical techniques [21][22][23][24][25][26], have been used for the determination of nickel in biological, food, natural water, and wastewater samples. Non-electrochemical methods have basic defects such as long analysis time, low sensitivity and expensive devices, therefore, specific pretreatment process is necessary before the analysis.…”

The new Micro‐set for Adsorptive Stripping Voltammetric Simultaneous Determination of Nickel and Cobalt Traces in Aqueous Media

“…Adsorptive stripping voltammetry has been most often utilized for trace, separate and simultaneous nickel and cobalt ions determination in various matrices as this method ensures: high sensitivity, low costs of analysis and relatively short time of measurements. For these determinations various electrodes were used to replace highly toxic mercury electrodes including: bismuth and lead film and bulk electrodes , antimony film electrodes , unmodified glassy carbon , ion exchanger‐modified carbon paste electrodes , carbon microelectrodes modified with metal film or metal microelectrode arrays .…”