Role of a Drastic Mechanical Treatment Toward Improving the Electrochemical Performance of a Solid-Gold Electrode

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination.

A simple and rapid approach for the electrochemical synthesis of Ag nanoparticles-coated gold nanoporous film (AgGNF) on a gold substrate was reported. The solid gold electrode (SGE) was directly anodized under a high potential of 5 V, and then reduced to obtain gold nanoporous film (AuNF) by freshly prepared ascorbic acid. The Ag nanoparticles (AgNPs) were grown on the AuNF electrode by potential-step electrodeposition. The resulting AgGNF composites electrodes were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and cyclic voltammetry (CV). As-prepared AgGNF electrode was used as a kind of superior sensor for Cr(VI) detection, which exhibited better electrocatalytic behavior than those of AuNF and SGE under identical conditions. Such a designed AgGNF nanocomposites electrode showed outstanding sensitivity (about 0.15 nA/ppb) and favorable reproducibility for Cr(VI) detection. The dependence of reduction current on Cr(VI) concentration is linear from 2 to 370 ppb with a low detection limit of 0.65 ppb. Interferences from other heavy metals ions (Cr3+, Cu2+, Pb2+, As3+ and Hg2+) associated with Cr(VI) analysis could be effectively diminished. The present method proves to be rapid, reliable, sensitive and low-cost.

Cyclic voltammetry (CV) on rotating Pt disc electrode was used for electrocatalytic oxidation of OH−. Hydroxide ion oxidation is followed by oxygen evolution with gas bubble formation. The image analysis was performed in situ in order to find correlation between bubbles related phenomena and the current of OH− oxidation. Bubble formation was tested in four different regimes having different scan rate and/or electrode rotation rate. The videometry using high speed camera was applied to observe the bubble related phenomena. The integral effect of presence of bubbles was analyzed. The fast Fourier transformation and normalized power spectra were used for advanced image analysis. Using this type of analysis, two different characteristic periodical behaviors were reported for the first time. The obtained periods were in accordance with scan rate and electrode rotation rate. The former periodic component of bubble formation process was correlated with well defined CV cycles, and hence, related to electrocatalytic oxidation–reduction of OH−. The other periodic component of bubble behavior induced by rotation rate (600 rpm) was shifted from 0.01 s toward slightly higher values probably due to hydrodynamic conditions in the investigated system.

First time, the electro-oxidative behaviour and determination of acotiamide at a pencil graphite electrode have been investigated under different experimental conditions using cyclic voltammetry (CV), differential pulse anodic stripping voltammetry (DPASV), and square wave anodic stripping voltammetric (SWASV) techniques. The voltammetric responses of acotiamide have been analyzed at different scan rates, pH and concentrations. Oxidation of acotiamide at the surface of pencil graphite electrode gave two well defined irreversible peaks in the voltammograms in BR buffer of pH 7.0. The oxidation process is completely diffusion controlled. A linear response of peak current has been obtained between 15.5 to 124 μM in non-aqueous media for all the voltammetric techniques. The proposed DPASV and SWASV techniques show limit of detection at 18.58 and 13.36 μM, respectively.

Square wave adsorptive stripping voltammetric determination of famotidine in urine

A measurement and speciation procedure for the determination of total mercury (HgTOT), inorganic mercury (HgIN), and methylmercury (CH3Hg) was developed and the applicability for on-site determination was demonstrated. A simple, portable sample pretreatment procedure was optimized to extract the analytes. Home-made columns, packed with a new sorbent material called CYXAD (CYPHOS 101 modified Amberlite XAD), were used to separate the two forms of the analyte. HgTOT and CH3Hg were determined by anodic stripping voltammetry (ASV), using a solid gold electrode (SGE). Two certified reference materials (BCR-463 Tuna Fish and Tuna Fish ERM-CE 464) and eight fresh fishes were analyzed. Then, the results that were obtained following the optimized portable procedure were compared with the concentrations obtained, using a direct mercury analyzer (DMA). This quantification, using the two techniques, demonstrated the good performance of the proposed method.

Anodic stripping voltammetry with gold electrodes as an alternative method for the routine determination of mercury in fish. Comparison with spectroscopic approaches.

Parameters affecting the determination of mercury by anodic stripping voltammetry using a gold electrode

The aim of this study was to develop a differential pulse anodic stripping voltammetry (DPASV) method for the rapid, sensitive and cost-effective determination and speciation of inorganic arsenic in aquatic environments. The electrochemical determination of arsenite and arsenate was investigated using a rotating solid gold electrode (SGE). As(III) was selectively determined at +0.1V by ASV after a deposition at -0.3V. The total As content (As(V)+As(III)) was electrochemically reduced at -1.2V by nascent hydrogen to As0, and then As(V) was evaluated indirectly by subtraction. Electrochemical reduction of As(V), instead of chemical reduction, was chosen to minimize the consumption of chemical reagents, reduce analysis time and provide a method suitable for on-site analysis. First, the operating parameters were optimized, and the method was characterized in terms of selectivity, sensitivity, linearity, precision and accuracy. A Limit of Detection (LOD) of 0.10μgL-1 was found for the developed technique for As(tot). The method was then applied to the direct quantitative determination and speciation of inorganic arsenic in real water samples; the results obtained showed satisfactory agreement with those produced by the hydride generation technique coupled with inductively coupled plasma atomic emission spectroscopy (HG-ICP-OES). Subsequently, the voltammetric determination of arsenic was explored with a portable potentiostat to evaluate the reliability of the procedure for on-site detection.

Dissolution of partially immersed nickel during in situ oxidation in molten carbonate: cyclic, stripping and square wave voltammetry measurements

The purpose of the study was to evaluate the effect of mechanical treatment and ion sputtering on hydrogen sorption and the mechanical properties of the surface of the membrane foil of the Pd-Cu solid solution system obtained by rolling. The efficiency of mechanical and ion beam treatment in cleaning of the surface of membrane foil of the Pd-Cu solid solution system obtained by rolling was assessed using cyclic voltammetry, Auger electron spectroscopy and atomic force microscopy. It was established that ion beam treatment (Ar+) and mechanical treatment reproduce the elemental composition of the surface, corresponding to the original composition of the solid solution, and forms a developed relief. The change in the asymmetry of the relief roughness after ion-beam treatment indicates the formation of microcracks on the foil surface, which reduce hardness and plasticity. Ion-beam surface treatment also contributes to the cleaning of the surface from rolling artefacts, which leads to a twofold increase in the ionization rate of atomic hydrogen, compared to a sample subjected to mechanical treatment

Electrochemical oxidation behavior of hydrochlorothiazide on a glassy carbon electrode and its voltammetric determination in pharmaceutical formulations and biological fluids

Voltammetry of dihydroxyphenylalanine ( l-DOPA) using a Nafion-coated carbon fibre ultramicroelectrode array

Polypyrrole-based potentiometric biosensor for urea part 1. Incorporation of urease

Higher stability constants for complexation of low valent, than of high valent, transition metal ions by saturated tertiary amine macrocyclic tetraaza ligands