Search results for "Electrode"
showing 10 items of 950 documents
Determination of titanium by adsorption voltammetry with 4-(2-pyridylazo) resorcinol
1990
Titanium (IV) forms a complex with 4-(2-pyridylazo) resorcinol (PAR) in weakly acidic solutions. This complex can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The current-concentration curve is linear from 0.15–4.8 ng/g. Ti at a deposition time of 3 min, the detection limit lies at 0.1 ng/g. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 1000-fold excess of iron by the standard addition method, albeit with decreased sensitivity.
A study on the adsorption voltammetry of titanium with various heterocyclic azo-compounds
1994
The voltammetric behaviour of various heterocyclic azo-compounds and their Ti-complexes was investigated at a stationary Hg electrode. In moderately acidic solutions Ti(IV) reacts with pyridylazo-compounds (PAR, 5-Br-PADAP, PAN), thiazolylazo-compounds (TAR, 5-Me-TAR, TAN, 4-Me-TAP) and pyrazolylazo-compounds (MDR, ERB) to form Ti-complexes, which are strongly adsorbed onto the Hg-electrode. These complexes are reduced at potentials more negative than those corresponding to the reduction of their respective ligands. The conditions for determining titanium by adsorption voltammetry using TAR and MDR as complexing agents were investigated in detail, as was the influence of foreign ions on the…
Study on the determination of trace rhenium (VII) by the adsorption differential pulse polarography
1989
The determination of trace rhenium (VII) by differential pulse polarography in the system of H2SO4-(NHsOH)2 · H2SO4-TeO2−4 is markedly improved by the addition of Nitron, which is adsorbed on the surface of mercury electrode. The limit of detection is down to 2 × 1010 M. The adsorptive peak potential is −0.80 V (vs. SCE). In the ranges of 5 × 1010—10−8, 1 × 10−5—10−7 and 1 × 10−7—10−6M, there are good linear relationships between the peak current increment and the concentration, of which the relative standard deviations are 9.5, 6.6, 1.8% respectively with the correlation coefficients of linear regression of 0.995–0.999. The results relating to this polarographic wave show that it is an ads…
Simultaneous homogeneous immunoassay of phenytoin and phenobarbital using a Nafion-loaded carbon paste electrode and two redox cationic labels
1997
Abstract The dual-analyte homogeneous immunoassay of two antiepileptic drugs was carried out simultaneously at physiological pH by square-wave voltammetry at a Nafion-loaded carbon paste electrode. Phenobarbital (PB) and phenytoin (DPH) were labeled by a cobaltocenium salt (Cc+) and a ferroceneammonium salt (N+Fc), respectively, and the corresponding standard redox potentials were −1.05 V and 0.26 V. Detection limits of 0.25 and 0.2 μM were achieved for PB-Cc+ and DPH-N+Fc (S/N = 3) after a 5-minute accumulation step, with linear responses over the 0.25–5 and 0.2–5 μM ranges, respectively. The relative standard deviation was evaluated to be ≥ 11% for 1 μM of each labeled drug. The separate,…
Electrochemical detection of chloride ions using Ag-based electrodes obtained from compact disc
2022
Abstract In this work electrochemical sensors fabricated from compact disc material (waste or new) are used to quantify chloride ions in different types of samples. All three electrodes, working, counter, and pseudo-reference electrodes, were fabricated from the compact disc and directly used. Different parameters were studied in order to demonstrate the possibility of using this waste material for efficient and low-cost electrochemical sensors. Chloride sensing performance was evaluated using linear scan voltammetry as the detection technique. A sensitivity of 0.174 mA mM−1 cm−2 with a limit of detection of 20 μM and excellent selectivity against many interferents was observed. Selectivity…
Voltammetric behavior and assay of the contraceptive drug levonorgestrel in bulk, tablets, and human serum at a mercury electrode.
2004
The cyclic voltammograms of levonorgestrel (LNG) in Britton-Robinson buffers of pH 2-11 at the hanging mercury drop electrode showed a single two-electron irreversible cathodic peak over the whole pH range. This peak may be attributed to the reduction of the 3-keto-delta-4-group in the A-ring of the LNG molecule. The interfacial adsorptive character of levonorgestrel onto the surface of the hanging mercury drop electrode was identified by means of both cyclic voltammetry and chronocoulometry techniques. A simple, sensitive, and selective square-wave adsorptive cathodic stripping voltammetric procedure was developed for the quantitation of levonorgestrel. Under the optimized operational cond…
Determination of NH(3) in pyrolysis gases by ammonia selective electrode.
1993
The suitability of ion-selective electrode for the determination of ammonia in pyrolysis gases of fossil fuels was studied. The ammonia was absorbed into acidic solution and two kinds of determination methods were carried out. The ammonia was either measured directly from the acid solution, or ammonia was first released into the gas phase and then determined (air gap method) by the ammonia selective electrode. The electrode functioned well in both cases, but the linear calibration range was rather narrow, slightly more than one tenfold. The quantitative detection limit in the water phase was 5 × 10−6M (0.085 ppm) NH3 and in gas phase operation solutions above 5 × 10−4M (8.5 ppm) NH3 it was …
Boron-Doped Diamond Electrodes for Electroorganic Chemistry
2011
Boron-doped diamond (BDD) electrodes provide an unusually wide electrochemical window in protic media, since there exist large offset potentials for the evolution of molecular hydrogen and oxygen, respectively. At the anode, alcohols are specifically converted to alkoxyl radicals. These can be used for chemical synthesis. When the enormous reactivity of such intermediate spin centers is not controlled, mineralization or electrochemical incineration dominates. Efficient strategies include either high substrate concentrations or fluorinated alcohols which seem to stabilize the spin centers in the course of reaction.
Characterization By Electroreflectance Of Thin Films And Thin Film Interfaces In Layered Structures.
1987
This paper reports investigations of ZnS quasi-amorphous films by electroreflectance (ER). The films were produced by thermal evaporation and their structure determined by electron diffraction. A voltage Vo cos cut was applied through the film with two evaporated Al electrodes. A lock-in amplifier gave 2 signals, Sf at f=ω/2π frequency and S2f at 2f frequency. The S2f spectrum, characteristic of the centrosymmetric bulk component of the film, reveals tails of localized states typical of amorphous semi-conductors. The Sf spectrum, characteristic of the interface layers with broken centro-symmetry, reveals tails of impurity levels which we attributed to diffusion of the electrode metal into t…
Effect of High Pressure on the Crystal Structure and Vibrational Properties of Olivine-Type LiNiPO4
2018
In this work, we present an experimental and theoretical study of the effects of high pressure and high temperature on the structural properties of olivine-type LiNiPO4. This compound is part of an interesting class of materials primarily studied for their potential use as electrodes in lithium-ion batteries. We found that the original olivine structure (α-phase) is stable up to ∼40 GPa. Above this pressure, the onset of a new phase is observed, as put in evidence by the X-ray diffraction (XRD) experiments. The structural refinement shows that the new phase (known as β-phase) belongs to space group Cmcm. At room temperature, the two phases coexist at least up to 50 GPa. A complete conversio…