Linear Stripping Voltammetry Research Articles

Electrodeposition of Amorphous Cobalt-Manganese Alloys on to Steel from Gluconate Baths

SUMMARYElectrodeposition of codeposited Co-Mn alloys on to steel substrates was obtained from an acidic gluconate bath. The effects of several plating variables such as current density, bath composition, pH and temperature, on the potentiodynamic cathodic polarisation curves, cathodic current efficiency of the deposited alloy as well as on the alloy composition were investigated. The codeposition of Mn and Co from these electrolytes follows the normal type of deposition. The cathode current efficiency, fCo-Mn% of the alloy is relatively high (» 95%). The Mn percentage in the deposits increases with either decreasing current density or increasing [Mn2+]/[Co2+] concentration ratio in the bath. Anodic linear stripping voltammetry (ALSV) indicated that the alloy might consist of a solid solution in which manganese is dissolved in cobalt. The Vickers microhardness of Co-Mn alloy electrodeposited from the present bath is higher than those of the parent metals. It is found that the Vickers microhardness values of the alloys are raised by decreasing pH or increasing current density. Increasing the electrolyte temperature greatly decreases the microhardness. These alloys were determined to be amorphous by X-ray diffraction analysis (XRD). Scanning electron microscopy (SEM) photomicrographs were obtained from the surfaces of selected deposits.

Test cells for plating

Highly adherent and compact copper coatings on steel substrates were successfully produced by electrodeposition using noncyanide bath based on glutamate as a complexing agent. The investigation was conducted using potentiodynamic cathodic polarization, cyclic voltammetry, in situ-anodic linear stripping voltammetry and chronoamperometry techniques. The results from the potentiodynamic cathodic polarization show polarization characterized by the presence of a current plateau (limiting current, ilim) in the potential range − 0.65 to − 0.83 VSCE, as a result of the deposition limitation by the diffusion process. The present glutamate bath has a higher cathodic current efficiency than that of cyanide baths. The electrochemical kinetic data confirms that the Tafel slopes of the solution containing glutamate ions are higher (821.1–849.9 mV decade− 1) than that without MSG (738.5 mV decade− 1). The relative invariance of αc, observed for increasing glutamate ion concentrations, suggests that the Cu electrodeposition pathway is not affected by the presence of glutamate. However, the rate of Cu2 + deposition on the steel surface from glutamate bath, is much higher than that on the glassy carbon surface. Copper coatings with very different morphologies can be obtained from the glutamate bath by simply manipulating the applied current density. X-ray diffraction analysis and SEM observations revealed that monosodium glutamate (MSG) does not vary the texture of the electrodeposited copper. However, it depends greatly on the deposition parameters such as the applied current density, pH and bath temperature. High hardness of copper deposits was obtained both at low concentration of MSG and at low current density. Baths contained glutamate ions exhibited a slight decrease in the throwing power.

Linear Scan Stripping Voltammetry at Glassy-Carbon Based Thin Mercury Film Electrodes for Determination of Trace Aluminium in Dialysis Fluids.

Linear scan cathodic stripping voltammetry at glassy-carbon based thin mercury film electrodes is a simple and inexpensive alternative for determining trace Al(III) in dialysis fluids. The efficiency of a variety of ligands (SVRS, Cupferron and Blue Black Eriochrome R) was evaluated comparing their voltamperometric response by application of a linear scan mode, after preconcentration into the mercury film electrode as Al(III) complexes. The best results were obtained when Cupferron was used as ligand, since its stripping current compares favourably in terms of sensitivity and resolution. The sharply defined cathodic peak at -1.3 V, corresponding to the reduction of the interfacial accumulated complex, could be used for quantitation. The response is linear up to 50 μg/l; correlation coefficient, 0.995. The relative standard deviation (at 20 μg/l level) is 3.5%, a detection limit of 0.5μg/l was estimated from the signal to noise characteristics of the response for 5 μg/l, which compares favourably among the reported electroanalytical methods for aluminium. We calibrated the method under conditions of use estimating the trace aluminium exposure in patients undergoing dialytic treatment.

Linear scan stripping voltammetry of copper(II) at the chemically modified carbon paste electrode

A new chemically modified electrode (CME), α-benzoinoxime (CUPRON) modified carbon paste electrode, for determining copper(II) is reported because of its excellent selectivity and sensitivity. The electrode is made by mixing a quantity of CUPRON (25%, w/w) with graphite powder (50%, w/w) and paraffin oil (25%, w/w). The CME preferentially deposits copper from the pH 8.5 NH3-NH4Cl buffer solution containing copper(II) under an open circuit and most of metal ions do not interfere with the measurements. The detection limit (S/N of three) for determining Cu(II) is 3 × 10−10 g/ml after 10 min accumulation in fast linear scan stripping voltammetric measurement. Linear calibration curves are obtained for Cu(II) concentration ranged from 1 × 10−8M to 1 × 10−6M. The response can be maintained with relative standard deviation of 6.0% in a 5 × 10−6M Cu(II) solution after eight accumulation/measurement/ regeneration cycles at the same electrode surface. The effect resulted from carbon paste preparation, reduction potential, electrode renewal, electrolyte and solution pH, preconcentration time, concentration dependence, possible interference and other variables has been evaluated. As for application, the CME demonstrates its high sensitivity and copper-selectivity in complex composition samples, such as anodic mud and polluted water.

Remote electrochemical monitoring of trace silver

A novel electrochemical sensor for remote monitoring of trace silver is described. The probe relies on linear scan stripping voltammetry at a newly-designed carbon-fiber working electrode assembly, connected to a 50-ft. long shielded cable. High sensitivity and selectivity are achieved while the probe is fully submersed in unaltered river-, lake- or groundwater samples. The optimization of various parameters has resulted in low detection limits (e.g., 0.3 μg/1 with 10 min accumulation) and good precision (relative standard deviation (R.S.D.) = 8% for n = 18 at 3 μg/1 silver). The new probe can operate over a broad pH and ionic-strength ranges relevant to natural water matrices.

Effect of impurities on gallate reduction in alkaline solution ? a linear stripping voltammetry study

Industrial production of gallium is mainly carried out by the electrolytic method using Bayer liquors of the aluminium industry. The major impediment to the effective recovery of gallium is known to be the presence of impurities (metallic and organic). Investigations on the effect of organics (aliphatic and aromatic) employing linear stripping voltammetry techniques on glassy carbon electrodes in alkaline gallate solutions revealed the inhibitive effect of these compounds on the electrodeposition of gallium and, hence, on gallium recovery from aluminate liquors.

Study on the polarographic catalytic wave of the system cobalt(II)-dimethylglyoxime

In the cobalt (II)-dimethylglyoxime-NH3-NH4Cl (pH 9) system, tne complex Co(II)A2 exhibits a sensitive polarographic wave. The mechanism of this catalytic wave has been investigated by linear potential sweep voltammetry, cyclic voltammerty and anedic stripping voltammetry. The experimental evidences showed that a zero-valence “active cobalt” or its complex formed during the irreversible reduction of Co(II)A2, which is adsorbed on the mercury electrode surface, and simultaneously DMG is catalytically reduced by this “active cobalt”. The mechanism of this system with the conflicting explanations of a catalytic hydrogen wave or only adsorptive complex wave is discussed.

Detemination of traces of metals by anodic stripping voltammetry at a rotating glassy carbon ring-disc electrode : Part 3. Evaluation of Linear Anodic Stripping voltammetry with Ring Collection for the Determination of Cadmium, Lead and Copper in Pure Water and High-Purity Sodium Chloride, and of Cadmium, Lead, Copper, Antimony adn Bismuth in Sea Water

A procedure based on linear anodic stripping voltammetry (a.s.v.) with ring collection is described for the determination of cadmium, lead and copper in very pure doubly-distilled water passed through a Millipore Milli-Q purification system and in commercial Suprapur sodium chloride. Concentrations of Cd, Pb and Cu as low as 6, 8 and 5 ng l −1 respectively, were measured in water and 0.12, 0.15 and 0.30 ng g −1 in sodium chloride. Results obtained for Cd, Pb, Cu, Sb and Bi in sea water by two different methods (linear a.s.v. with a ring-disc electrode and differential pulse a.s.v. with a hanging mercury drop electrod) were in good agreement for u.v.-irradiated samples; linear a.s.v. with the ring-disc electrode gave systematically higher Cd, Pb and Cu contents because of exchange of mercury(II) ions added to the solution, with the heavy metal non-labile complexes.

Determination of traces of metals by anodic stripping voltammetry at a rotating glassy carbon ring-disc electrode : Part 2. Comparison between linear anodic stripping voltammetry with ring collection and various other stripping techniques

Linear anodic stripping voltammetry (a.s.v.) with ring collection is compared with differential pulse a.s.v. at a hanging mercury drop electrode and with linear or differential pulse a.s.v. at a mercury film rotating electrode. Sensitivity, detection limits, resolution, base-line, the concentration range covered, the influence of organic compounds in the sample, and operational ease are discussed. The main conclusions are as follows: differential pulse a.s.v. at a hanging mercury drop electrode is best suited for determining heavy metal concentrations of the order of μ l -1; the differential pulse mode at the rotating disc electrode or the d.c. mode at the rotating ring-disc electrode are required for sub-μ l -1 concentrations; the limits of detection for the determination of cadmium, lead and copper are in the 2–5 ng l -1.

Alternating current linear sweep and stripping voltammetry with phase-selective second harmonic detection

Alternating current linear sweep and stripping voltammetry with phase-selective second harmonic detection