Cathodic Electrode Reaction Research Articles

Electrochemical and liquid chromatographic analysis of triamcinolone acetonide in pharmaceutical formulations

Electrochemical reduction of triamcinolone acetonide on pencil graphite electrode surface was firstly investigated by cyclic voltammetry (CV). The dependence of cathodic peak current and peak potential on different pH medium and scan rate were investigated. The adsorption controlled nature of the peak was achieved. During pH optimization, 0.067 M Phosphate (pH 4.50 to pH 7.50), 0.2 M Acetate (pH 3.50 to 5.50) and 0.04 M Britton Robinson (BR; pH 2.00 to 12.00) buffers were employed as supporting electrolytes. Scan rate optimization was investigated in the range 25-1000 mVs-1 (vs. Ag/AgCl). Maximum peak current was observed in the 0.04 M BR buffer (pH 3.50). Peak current increases and shifts to more cathodic values with the increasing scan rate. Curve of logarithm of peak current (log I) versus logarithm of scan rate (log v) showed linear regression with the equation log(Ip/μA) = 0.8395 log(v/mVs-1)-0.8386 and correlation coefficient (R2: 0.9761). This indicated that slope of the logv-logI curve is close to 1.0 and the cathodic electrode reaction was adsorption controlled, as desirable. The linear range was 1×10-7-5×10-5 M, sensitivity was 1,3347 µA M-1, Limit of detection (LOD) and Limit of quantification (LOQ) were 3.18×10-8 M and 1.00×10-7 M, respectively. HPLC-PDA analysis were performed with H2O:MeOH (28:72, v/v) as mobile phases A and B at a flow rate of 1mL/min at 242nm. Method validation studies were conducted in accordance with ICH Q2(R1) guideline and corresponding results were summarized in tables. HPLC-PDA method displayed linearity in 0.1-50µg/mL (2.3×10-7-1.15×10-4 M) concentration range with LOD and LOQ values as 3.992×10-8 and 1.29×10-7M, respectively.

Biophysikalische Grundlagen der Anwendung elektromagnetischer Felder zur Beeinflussung der Osteogenese

The interactions between bone-forming cells and the extracellular processes determining the mineralisation of the osteoid with electric and/or magnetic fields is the elementary prerequisite. The magnetic or electric field or the combination of both, as well as their time related intensity are discussed as the stimulating factors. When using electric current there is a physical process to be considered. This process consists of changes of metabolites caused by the cathodic electrode reaction which may gain influence on the metabolism of bone-forming cells and the mineralisation. According to the results of this investigation the bone-producing effect of the cathodic electrode reaction saturates+ at a geometric current density of about 0.4 microA/mm2. Apart from the changes of metabolites produced by the electric current there are electric polarizations in front of interfaces and cell membranes due to local ion concentrations caused by even very weak electric fields.

Experimental measurements and numerical simulations to evaluate the electrode kinetics for 316 stainless steel under PWR-relevant conditions

The local environment in an occluded region of a pressurized water reactor (PWR) depends on its geometry, its access to the bulk and the nature of the electrode kinetics at the metal surfaces. In PWR-relevant, oxygen-free, boric acid–lithium hydroxide solutions the dominant anodic and cathodic electrode reactions are found to be hydrogen oxidation and water reduction, respectively. The hydrogen oxidation reaction kinetics have been quantified using potentiostatic measurements – at 300°C, under various dissolved hydrogen concentrations, for 1000ppmB and 2ppmLi. The reaction kinetics have been verified by modelling of a crevice experiment performed in an autoclave at 300°C for 1000ppmB, 2ppmLi and 25 STP ccH2/kg.

Determination of inorganic phosphate in a soil extract using a cobalt electrode

In soil and environmental science, a sensitive and accurate phosphate sensor would constitute a very useful tool. Several designs, mainly potentiometric and amperometric, have been published, but no commercial sensor exists. Recently, a cobalt electrode has been shown to respond to phosphate in solution. This electrode is extremely simple and robust. In this work, the cobalt electrode applicability to the measurement of phosphate in ammonium lactate-acetic acid (AL) extracts of soils was investigated. The slope of the calibration curve was -30 mV/decade; the linear part corresponded well with the concentration range usually encountered in AL extracts. Dissolved organic substances caused the electrode potential to drift and the extracts were therefore shaken with carbon black prior to measurement. Iron was shown to interfere, most likely by participating in the cathodic electrode reaction.

Direct electrocatalytic determination of dissolved peroxidases

A novel voltammetric approach is described for the quantification of dissolved redox enzymes. The measurement of horseradish peroxidase and microperoxidase is based on the electrocatalytic current generated when the enzyme reduces hydrogen peroxide to water and oxidises at low potential a mediator which is regenerated in a cathodic electrode reaction. Since the mediator regeneration is sufficiently fast, the overall reaction rate is determined by the enzyme activity. As a consequence stationary current-time curves are obtained in dependence on the activity of peroxidase in solution. For the chemical modification the electrode was modified with 1-(N,N-dimethylamine)-4-(4-morpholine)benzene, a mediator of low solubility in reduced form and with favourably low formal potential. At a working potential of − 50 mV vs. 0.1 M Ag AgCl cathodic steady-state currents were obtained after injection of peroxidase in the presence of 1 mmol/1 hydrogen peroxide. The detection limit for horseradish peroxidase and microperoxidase-11 were 10ng/ml (250 pmol/1) and 20 ng/ml (10 nmol/1), respectively.

Steric effects in electrode processes: Discharge process of the lead citrate complex on a mercury electrode covered by monolayers of aliphatic alcohols

The discharge of the lead citrate complex (PbL 2−) on a mercury electrode covered by n-hexanol or n-heptanol molecules has been investigated by means of polarographic and chronocoulometric methods. The relation between the bulk surfactant concentration and the rate of the electrode reaction was examined. An average value of the steric factor r ≠/ r i equal to 4.0 ±0.2 was found for the cathodic electrode reaction occurring in aqueous solutions of sodium citrate containing aliphatic alcohols. The kinetic and mechanistic implications of an increase in the reactant size under such conditions are discussed.

Electrochemical reactions of pyrite in acid perchlorate solutions

Pyrite has been subjected to electrochemical measurements in 1M HClO4 to determine anodic and cathodic electrode reactions. Under anodic conditions only ferric and sulphate ions are formed, while under cathodic conditions ferrous ions and H2S are discharged, with hydrogen. If oxygen is present, its reduction will cause an additional increment of cathodic current.Ordinary pyrite, exposed to air, exhibits a rest potential of about +0.62 volt (vs. SHE) which is more noble than for any other sulphide mineral. Cathodic excursions that generate H2S and leave a clean pyrite surface when the soIi[~on is bub bled with helium lead to rest potentials of between 0.2 and 0.3 volt, much more consistent with the thermodynamically estimated reversible potential of pyrite. The 0.62-volt value is therefore regarded as evidence of a ‘passive’ condition. Thus, between 0.3 and 0.6 volt, passive pyrite is cathodic, while ‘active’ pyrite is anodic Résumé On a fait des mesures électrochimiques sur la pyrite dans HClO4 1M afin de determiner les réactions d'électrodes anodiques et cathodiques. A l'anode on ne forme que des ions ferriques et des ions sulfate alors qu'à la cathode des ions ferreux et H2S sont déchargés en mê;me temps que de l'hydrogéne. S'il y a de l'oxygène il y a augmentation du courant cathodique provenant de sa réduction.La pyrite ordinaire ayant été exposée a l'air présente une tension de coupure d'environ '0.62 volt (par rapport à ESH) ce qui est plus élevé que pour tout autre sulfure minéral. Quand il y a un barbotage d'helium dans la solution les réactions cathodiques qui liberent H2S et laissent une surface de pyrite propre conduisent à des potentials de coupure compris entre 0.2 et 0.3 volt. Cette mesure est plus en accord avec la valeur estimée du potentiel réversible de la pyrite. La valeur 0.62 volt met done en évidence un état ‘passif’. Done entre 0.3 et 0.6 volt, la pyrite passive est cathodique alors que la pyrite ‘active’ est anodique.