Search results for "Volt"
showing 10 items of 2187 documents
Contribution to the adsorption voltammetric determination of manganese
1994
The adsorption voltammetric determination of Mn(II) with Bromopyrogallol Red (BPR) and Mordant Red 19 (MDR) has been investigated using a hanging drop mercury electrode. In NH3/NH4Cl solution, ligands and Mn(II) complexes give well separated voltammetric peaks after enrichment onto the electrode. The conditions for determining manganese by adsorption voltammetry with these reagents have been investigated in detail, as has the influence of foreign ions on the determination. The detection limits are 4·10−10 mol/L Mn for BPR and 8·10−10 mol/L Mn for MDR, respectively.
Screening and authentication of tea varieties based on microextraction-assisted voltammetry of microparticles
2015
Abstract A simple electrochemical methodology for screening and authentication of green, black and red tea varieties is proposed. It is based on the record of the voltammetric response of microparticulate films of antioxidant compounds resulting from an ethanolic micro-extraction of commercial tea herbal preparations in contact with aqueous buffers. The obtained voltammetric responses led us to differentiate between diverse tea varieties upon application of bivariant and multivariant chemometric techniques, including discrimination of mixtures of teas with sensitivity estimated of 5.0 μA mg −1 with a detection limit of 0.01 mg of tea sample. Under the proposed conditions 100% discrimination…
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…
Determination of titanium by adsorption-voltammetry with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP)
1990
The 1:1 complex between titanium (IV) and 5-Br-PADAP can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The detection limit is 3×10−10 mol/l Ti (0.015 ppb). Calibration curves are linear for solutions containing 4×10−10 to 5×10−8 mol/l Ti(IV) and an enrichment time of 3 min. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 5000-fold excess of iron.
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…
Vanadium and molybdenum concentrations in particulate from Palermo (Italy): analytical methods using voltammetry
2014
The main purpose of this work was to develop a reliable method for the determination of vanadium (V) and molybdenum (Mo) in atmosphere particles or aerosols because they can not be readily measured using conventional techniques. For this research, 30 particulate samples were collected from five different stations located at Palermo, Italy. We used the catalytic adsorptive stripping voltammetry and differential pulsed voltammetry to measure Vand Mo in atmospheric particulate, respectively. The represented method includes advantages of high sensitivity, high selectivity, simplicity, reproducibility, speed and low costs. The quantification limits for V and Mo are, respectively, 0.57 and 0.80 n…
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…
Dialkyl(butadiene)cyclopentadienylmolybdenum(III) Complexes. Synthesis, Characterization, and Reactivity
2000
International audience; Treatment of CpMo(η4-diene)Cl2 (diene = 1,3-butadiene, C4H6, 1‘; isoprene, C5H8, 1‘ ‘; 2,3-dimethyl-1,3-butadiene, C6H10, 1‘ ‘) in diethyl ether at low temperature with 2 equiv of alkylmagnesium RMgX reagents affords the corresponding dialkyl complexes CpMo(η4-1,3-diene)R2 (2, 2‘, 2‘ ‘, R = CH3, a; CH2Ph, b; CH2SiMe3, c). These species are isolable in moderate yields and have been fully characterized by EPR, elemental analyses, and cyclic voltammetry. They all show a reversible reduction process at relatively low potentials and an irreversible oxidation. The structure of 2‘ ‘a was confirmed by single-crystal X-ray diffraction. The mixed complex CpMo(η4-C4H6)Cl(CH3), …