Vanadium Salts Research Articles

Rare Earth-Based Compounds as Inhibitors of Hot-Corrosion Induced by Vanadium Salts.

In this study, the performance evaluation of lanthanum compounds as corrosion inhibitors of vanadium salts was performed. The inhibitors tested were lanthanum acetate and La2O3. The performance of the inhibitors was tested using sodium metavanadate (NaVO3) as a corrosive medium at 700, 800, and 900 °C. The corrosion inhibitory effect was evaluated on the corrosion process of 304H stainless steel. The corrosion rate of the steel was determined by the mass loss technique after 100 h of immersion in the corrosive salt with and without the addition of the corrosion inhibitor. The results show that lanthanum compounds act as corrosion inhibitors of vanadium salts. The inhibitory effect increases by increasing the concentration and tends to decrease when increasing the test temperature. Lanthanum compounds act as excellent corrosion inhibitors due to their ability to stabilize vanadium cations. Vanadium is stabilized by forming a new compound, lanthanum vanadate (LaVO4), with a melting point much higher than the compounds formed when Mg or Ni compounds are used as corrosion inhibitors.

Инсулиномиметически активные макромолекулярные металлокомплексы ванадия на основе поли-N-винилпирролидона. Часть 1. Синтез макромолекулярного металлокомплекса ванадия и оценка его острой пероральной токсичности

Diabetes mellitus (DM) is a severe chronic disease affecting virtually all kinds of metabolic processes in the human body. As incidence and prevalence of DM are increasing worldwide, WHO estimates the number of people living with diabetes to be as high as half a billion and still rising. Long-term health complications of DM, such as diabetic nephropathy, retinopathy, neuropathy, and cardiovascular pathology, although preven-table in most cases, are known to be severe, potentially life-threatening and often irreversible, which makes the search for new effective antidiabetic drugs a research priority and one of the most pressing issues in health care today. To date, the insulin-mimetic properties of vanadium compounds have been the subject of quite a significant number of studies. In vivo experiments have shown that vanadium, acting in an insulin-like fashion, takes part in the regulation of glucose and lipid metabolism. In particular, vanadium stimulates glucose uptake and metabolism in insulin target tissues, increases the intensity of glycogen and lipid biosynthesis, and inhibits that of gluconeogenesis, glycogenolysis, and lipolysis. Organic vanadium complexes are known to be less toxic than its inorganic salts, which are characterized by a number of potentially serious adverse effects, mainly but not exclusively on the central nervous system and the kidneys; in addition to lower toxicity, organic vanadium compounds have been found to have higher bioavailability when to compared to those of inorganic nature. Such observations clearly hold promise for the development of an entirely novel therapeutic class of antidiabetic drugs. The aims of this study are to obtain new polymeric vanadyl(VO2+) derivatives based on poly-N-vinylpyrrolidone (PVP) that would exert hypoglycemic effect in vivo, and to explore the possibilities of using such compounds or formulations derived thereof for type 2 DM prophylaxis and/or treatment. This work gives a method of obtaining and isolation of an oxovanadium(IV)-polymer metallocomplex, and describes the structural features of said compound, confirmed experimentally. The results of the acute oral toxicity study revealed that the newly synthesized compound is of low toxicity, having a median lethal dose (LD50) that is at a level well above those typical of inorganic vanadium salts.

Facile solid-state synthesis for producing molybdenum and tungsten co-doped monoclinic BiVO4 as the photocatalyst for photoelectrochemical water oxidation

BiVO4 has been widely applied as photocatalysts for water oxidation, owing to preferable band configuration and small band gap for absorbing wide range of light. Synthesizing BiVO4 is usually based on wet routes, which are more complex and require extra steps for separating photocatalysts from solutions. A novel solid-state synthesis is firstly proposed in this study to efficiently synthesize BiVO4 by simply mixing bismuth and vanadium salts without other mediums and directly annealing the mixture at 450°C. Heteroatom-doping of BiVO4 is also achieved by annealing the mixture of W and Mo salts along with bismuth and vanadium precursors to increase the carrier concentration and accelerating the charge transfer. The W and Mo co-doped BiVO4 electrode with the W:Mo ratio of 1:1 shows the highest photocurrent density of 0.21 mA/cm2 at 1.23 V versus reversible hydrogen electrode and the smallest onset potential of 0.686 V versus reversible hydrogen electrode under air mass 1.5 solar illumination. This study successfully realizes the efficient fabrication of BiVO4 and the incorporation of W and Mo dopants using the solid-state synthesis. Applying this manner cannot only reduce the synthesis time but also provide more precise control of the element composition. Further developments of the co-catalyst/photocatalyst system are expected to be realized by applying this novel solid-state synthesis.

Developing Vanadium as an Antidiabetic or Anticancer Drug: A Clinical and Historical Perspective.

Vanadium has been known for centuries to have beneficial effects on health and has the potential to be used as an alternative to other diabetic and anticancer medicines. The beneficial effects of vanadium salts or organic compounds have been explored in vitro, ex vivo, and in vivo in animal and human studies. A consensus among researchers is that increased bioavailability of these compounds could markedly increase the efficacy of this class of compounds. In addition, because many commercially available vanadium derivatives are being used by body builders to enhance performance, more understanding of their mode of action is desirable. Future studies of various vanadium compounds need to evaluate their biodistribution, biotransformation, and the effects of food and formulation on the bioavailability of the compounds. To date, most studies in humans have employed vanadium salts, mainly vanadyl sulfate, and dose-limiting side effects were reported at therapeutic doses. One organic vanadium compound, bis(ethylmaltolato)oxovanadium(IV), had improved efficacy compared to the vanadyl sulfate and was selected for Phase 1 and 2 clinical trials. Future studies should be conducted as randomized, placebo controlled trials lasting several months, with monitoring of both fasting blood glucose and hemoglobin A1c. Now, the most promising potential uses of vanadium compounds are as nutritional supplements to control glucose levels and perhaps, as an anticancer agent potentiated by immunotherapy.

Effect of copper and vanadium ions on morphology of carrot (Daucus carota L. subsp. sativus (Hoffm.) Schübl. & G. Martens) and wheat (Triticum aestivum L.) plants

In the whole world, researches are conducting on toxic effect of heavy metals on living organisms. The problem with heavy metal occurrence in the environment is not only associated with their toxicity, but also with their ability to accumulate inside living organisms. This study presents the effect of copper and vanadium ions on germination and growth of carrot (Daucus carota L subsp. sativus (Hoffm.) Schübl. & G. Martens.) and winter wheat (Triticum aestivum L.). The experiment was carried out in two independent series with ten repetitions each. The water solutions of copper (CuSO4) and vanadium (H4NO3V) salts with the concentrations: 0.6 mM, 0.3 mM, 3 mM and 6 mM were used. The control groups were objects watered with distilled water. The conducted experiment showed that, the copper and vanadium ions had negative effect on germination and growth of plants. With the increasing of concentration of heavy metal ions an inhibition of seeds germination capacity was observed. The length of D. carota and T. aestivum seedlings in each salt solutions was inhibited, compared to the control group. During the growth phase, the stimulation of wheat leaves growth, only on copper solutions with concentration 3 mM and 6 mM was observed. Changes of a fresh and dry weight, and a water content were observed, depending on the copper and vanadium ions concentration.

Chemical Conversion Treatment on Stainless Steel 316L By Using TiO2 Thin Films Via Sol-Gel Technique and Adding Niobium and Vanadium As Inhibitors to Enhance Corrosion Resistance

Stainless steel has been used in a wide variety of industries due to its mechanical, anticorrosion and biocompatibility properties. However, its passive layer can be compromised under aggressive environments leading to corrosion. There are several chemical conversion treatments that are applied on the steel’s surface to improve its corrosion resistance. The most commonly used conversion coatings are based on hexavalent chromium, a compound that is carcinogenic and very hazardous pollutant. The new researches are looking for alternatives that achieve the same or better corrosion inhibition. As an alternative less toxic method, this work presents the use of the sol-gel as a chemical conversion treatment to obtain TiO2 thin films on a stainless steel 316L.. The sol-gel was prepared with titanium butoxide as a precursor; adding niobium and vanadium salts as corrosion inhibitors. Once prepared, the sol-gel was aged for 24 hours. The substrate (stainless steel 316L) was cut in 5x2cm pieces to be ground and polished. Each piece was rinsed with water and finally with acetone. The method dip-coating was used to apply the sol-gel on the surface of the substrate. The dipping was done at three different speeds using a device previously designed and built in the laboratory. After the sol-gel is applied, the pieces are heat treated at different temperatures: 300°C, 500°C and 700°C. The films were characterized by X- Ray Fluorescence and Raman Spectroscopy. These techniques showed the presence of TiO2, with different structures depending on the thermal treatment temperature: amorphous, anatase and rutile. The corrosion behavior was studied in a 3% NaCl solution by Potentiodynamic Polarization Curves and Electrochemical Impedance Spectroscopy. The effect of the dipping speed and the actual TiO2 structures on the anticorrosive properties were reported.

(Invited) Organic Molecules for Redox Flow Batteries

The need for grid-scale electricity storage demands cost-effectiveness and durability beyond the reach of current Li-ion battery technologies. Redox flow batteries (RFB) decouple energy from power that promise low cost for long discharge duration as required for load shifting, and they offer long cycle lives as no phase change occurs in the electrodes. However, the most mature RFB technology relies on vanadium salts, whose high and volatile cost threatens its practicality. Among alternative redox couples, organic molecules are emerging with a high promise for their projected low cost and versatility in terms of providing various properties desired in a RFB. In this talk, I will focus the attention on the use of quinone molecules for aqueous RFBs. I will start with molecular selection and design strategies that have been successfully applied to tune the redox potential, the solubility, and the stability of quinones. I will then discuss the engineering aspects of delivering the promise of quinone molecules in stable, high-performance RFBs. I hope that the talk will provide a comprehensive overview of the application of organic molecules in RFBs and stimulate new ideas for exploiting organic materials for energy storage.

Sequentially-processed Na3V2(PO4)3 for cathode material of aprotic sodium ion battery

Na3V2(PO4)3 is considered as one of the most promising cathode materials for SIB, electrodes through exploiting unconventional and relatively expensive vanadium salts or carbon sources. For the latter, the obtained superior rate performance is generally obtained at relatively high content of the carbon additives. A carbon-coated sodium ion containing vanadium phosphate, Na3V2(PO4)3, is prepared by a simple sequentially-processed method. The sequentially-processed method is potential for mass-production and preparation of other high-quality vanadium-based electrode materials. A special dissolution sequence leads to an un-precipitated solution, which is used to produce an amorphous-state precursor. The carbon mass fraction of sequentially-processed Na3V2(PO4)3 is estimated to be less than 2% measured by thermo-gravimetric analyzer. Electrochemical performance of sequentially-processed Na3V2(PO4)3 is examined as cathode material for aprotic sodium ion battery. The sequentially-processed Na3V2(PO4)3 delivers 113 mA h g−1 with a flat voltage plateau at 3.4 V vs sodium metal. The simple sequentially-processed method also endows excellent rate capacity and cyclability to sequentially-processed Na3V2(PO4)3 at the voltage window of 2.8–3.8 V. We further investigate cyclic and rate performance of sequentially-processed Na3V2(PO4)3 as a high-capacity cathode material with a widened voltage window of 1–4 V vs Na+/Na. A capacity of more than 210 mA h g−1 can be delivered with appearance of another additional voltage plateau at 1.6 V but the capacity quickly fades away after dozens of cycles. The result validates the potential of Na3V2(PO4)3 in reaching high cathode capacity (> 200 mA h g−1) and also calls for new structure design to better accommodate the intercalation of sodium ions and new binder materials that can tolerate a larger degree of electrode expansion.

The role of phosphate additive in stabilization of sulphuric-acid-based vanadium(V) electrolyte for all-vanadium redox-flow batteries

Catholyte in all-vanadium redox-flow battery (VRFB) which consists of vanadium salts dissolved in sulphuric acid is known to be stabilized by phosphoric acid to slow down the thermal aging at temperatures higher than 40 °C. To reveal the role of phosphoric acid, the thermally-induced aggregation is investigated using variable-temperature 51V, 31P, 17O, 1H nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS). The results indicate that the thermal stabilization of vanadium(V) electrolyte is attained by the involvement of monomeric and dimeric vanadium(V) species in the reaction with phosphoric acid which is concurrent to the formation of neutral hydroxo-aqua vanadium(V) precipitation precursor. The dimers are stabilized by counter ions due to association reaction or if such stabilization is not possible, precipitation of vanadium pentoxide is favored. The evolution of particles size distributions at 50 °C in electrolyte samples containing 1.6 M vanadium and 4.0 M total sulphate and the pathways of precipitate formation are discussed. The optimal total phosphate concentration is found to be of 0.15 M. However, the induction time is assumed to be dependent not only on the total phosphate concentrations, but also on the ratio of total vanadium(V) to sulphate concentrations.

Thermodynamics of Polymer Electrolyte Membranes in Contact with Concentrated Electrolyte Solutions

In this study, we build off our recent development of a database of data describing the composition of polymer electrolytes in contact with various acids, bases and salts. This situation is common in practical electrochemical systems such as redox flow batteries and electrochemical reactors. For example, the vanadium redox flow battery (VRFB) electrolyte solutions consist of several molar solutions of aqueous sulfuric acid (with other acids used in certain cases) and up to 2M vanadium salts. As we have shown, these concentrations cause the general phenomenon of breakdown of the Donnan exclusion effect in a variety of polymer electrolyte membranes, both cation and anion exchanging membrane types.1,2,3 A description of these processes would be useful in helping to separate the effects of various modifications of the membrane composition and structure on its behavior. We develop the groundwork for a thermodynamic description of uptake of ionizable species by polymer electrolyte membranes in contact with concentrated solution electrolyte solutions using the VRFB membrane-electrolyte combination as our test case. We note that all such descriptions of the behavior of polymer systems entails the assumption of a ‘local’ equilibrium, relevant for short times. Here the adjective short refers to times long enough for uptake processes to occur but short enough that the polymer itself does not have time to change from its initial state, set by its thermal history. This allows us to assess membranes that might be thermally ‘re-arranged’ as separate entities, thus isolating any effects of the treatment. We first develop a description of the local equilibrium of the acid solution with the membrane. As Tang et al showed,1 this has several interesting features that are generic to acid uptake into Nafion and related polymer electrolytes. A convenience of this approach is the broad availability of descriptions of the acid solution properties. Once a description of the acid-membrane equilibrium is available, we proceed to consider the situation with added vanadium. For simplicity, we will begin by developing the case for VOSO4 solutions in acid. In this case, we need to reassess the solution thermodynamics, adding some measurements specific to a given ternary composition. We will describe these measurements in the oral presentation. Acknowledgements We gratefully acknowledge the support of this work by the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability (Dr. Imre Gyuk) and by the Office of Naval Research. We also thank 3M for providing membranes.

A potential Cu/V-organophosphonate platform for tailored void spaces via terpyridine mold casting.

The reaction of appropriate copper and vanadium salts with tetratopic methane tetra-p-phenylphosphonic acid (MTPPA) in the presence of 2,2':6':2''-terpyridine (terpy) yielded the three-dimensional bimetallic copper vanadium phosphonate framework [{Cu(terpy)}4Cu(VO2)4(MTPPA-H)2]·4H2O (1). Terpy has no net contribution to the three-dimensional structure providing a potential platform for void space formation via mold-casting. The structure was characterized by single-crystal X-ray diffraction and thermogravimetric analysis (TGA). Magnetic measurements were performed using a SQUID magnetometer. The crystal structure of the methanol solvate of the free ligand, MTPPA·MeOH, was analysed using Hirshfeld surfaces and fingerprint plots.

High Temperature Corrosion of Nickel in NaVO3-V2O5Melts

Many alloys used at high temperature in industrial processes are Ni-based and many others contain it in appreciable quantities, so it is of interest to evaluate the performance of pure nickel in order to determine the behavior of its alloys once the elements responsible for their protection have been depleted due to accelerated corrosion processes in the presence of vanadium-rich molten salts. Due to this, this work presents the study of Ni behavior in NaVO3-V2O5mixtures at different temperatures. The behavior of pure nickel was determined by both electrochemical and mass loss measurements. The results show that the aggressiveness of the vanadium salts is increased by increasing both the V2O5content and temperature. V2O5addition considerably increases the current densities of the anodic and cathodic reactions. The corrosion process of Ni is modified due to the presence of its corrosion products, and its presence increases the activation energy by at least one order of magnitude. Although nickel shows a high reactivity in vanadium-rich salts, its reaction products are highly stable and protect it from the corrosive medium because the corrosion reactions trap the vanadium and block the migration of nickel ions.

Synthesis of Copper Nanoparticles in Ethylene Glycol by Chemical Reduction with Vanadium (+2) Salts.

Copper nanoparticles have been synthesized in ethylene glycol (EG) using copper sulphate as a precursor and vanadium sulfate as an atypical reductant being active at room temperature. We have described a technique for a relatively simple preparation of such a reagent, which has been electrolytically produced without using standard procedures requiring an inert atmosphere and a mercury cathode. Several stabilizing agents have been tested and cationic capping agents have been discarded owing to the formation of complex compounds with copper ions leading to insoluble phases contaminating the metallic nanoparticles. The elemental copper nanoparticles, stabilized with polyvinylpyrrolidone (PVP) and sodium dodecyl sulphate (SDS), have been characterized for composition by energy dispersive X-ray spectroscopy (EDS), and for size by dynamic light scattering (DLS), and transmission electron microscopy (TEM), giving a size distribution in the range of 40–50 nm for both stabilizing agents. From a methodological point of view, the process described here may represent an alternative to other wet-chemical techniques for metal nanoparticle synthesis in non-aqueous media based on conventional organic or inorganic reductants.

Wet Chemical Approach for Vanadium Doped Maghemite (Fe2-xVxO3) Nanocrystals

Background: Nanomaterials are widely synthesized by wet chemical routes. Magnetic nanoparticles with size ranging from 2 to 20 nm are of significant importance, resulting in a unique magnetic property of the nanoparticles. Maghemite nanostructures with partially disordered (Fe3+)[Fe5/3⁏1/3]O4 structures, undergo cation-insertion reactions without resorting to a drastic change in the material composition. Tailoring the superparamagnetic properties of nanoparticles by doping with transition metals, such as vanadium could be advantageous, as it would provide control over properties that are important for biological applications, such as magnetization dependent changes in temperature, relaxivity, and hysteresis. Method: We describe the obtention of vanadium doped maghemite (Fe2-xVxO3) from colloidal suspensions of vanadium and iron salts, using a precipitation–annealing method. A single step simpler synthesis scheme has been proposed in this work, with annealing temperature (350 °C), for a short period of time (~ 15 minutes), in order to achieve smaller in size but developed nanocrystals. Results: Superparamagnetic vanadium doped maghemite with particles (~8 nm) size has been synthesized. For the first time, vanadium up to 5 mol% has been doped on maghemite nanocrystals and characterized successfully for the presence of stable V3+. These results open a new era of vanadium applications in industrial Nanosciences; possessing superparamagnetic properties. Conclusion: A wet chemical route to direct the synthesis of vanadium doped γ- Fe2O3 nanocrystals, has been studied. The doping controls the crystallite size by occupying the vacant octahedral spaces available in the cubic system (space group P4332) maghemite crystals. High surface area magnetic particles, with an average size of ~8 nm were obtained. Keywords: Characterization, synthesis, vanadium doped maghemite.

Investigation of Vanadium Oxidation States in Sulfuric Acid by Voltammetry and Electrochemical Impedance Spectroscopy

Vanadium has several soluble oxidation forms which can be used as the oxidized and reduced side of an electrochemical cell. This is the basis of the so called redox flow battery. A redox flow battery is an applied technological system from which electrical energy is derived using the electrochemical reaction of the higher and lower oxidation state of a pair of solutions. Our aim was to carry out more fundamental studies of the redox processes on graphite electrodes in solutions of vanadium salts. The experimental setup was using a rotated disk electrode and voltammetric, and impedance measurements were performed.

Voltammetric and Impedance Investigation of Vanadium Oxidation States in Sulfuric Acid

Redox flow battery is a system in which energy is derived from electrochemical reaction of a pair of solutions, of which one is reduced and the other is oxidized during discharge; the opposite process then takes place during charging. One such system is based on solutions of vanadium in several states dissolved and supported by SO4 2-anion in sulfuric acid. In principle, the starting material for both the positive and negative electrode electrolyte is identical, therefore, mixing of the two solutions through leakage or accident will lead to discharge, but not to chemical degradation of the stock material. Therefore, vanadium redox flow cells enjoy lot of attention in the energy storage industry. Our aim was to carry out more fundamental studies of the redox processes on graphite electrodes in solutions of vanadium salts. The experimental setup was using a rotated disk electrode and voltammetric, and impedance measurements were performed. Data obtained from impedance measurements enjoy lot of attention in electrochemical studies, because they provide wealth of information relevant to static, as well as dynamic, parameters of the system. The nature of proper impedance data collection (and successful interpretation) requires that the data be collected while the system under observation is stable, at equilibrium, although the equilibrium can be static, as well as dynamic. With this requirement in mind, and also due to some complexity, most impedance analyzers (or their software) will not perform other task while impedance data are taken. However, with fast instrumentation, slow change in bias polarization, deemed sufficiently benign to operate at a (pseudo)equilibrium of the system, should allow impedance data collection as a function of the bias potential. We present here data taken with Solartron ModuLab setup, which we programmed to perform extremely slow potential scans, and to collect simultaneously impedance data. A control study was performed on potassium hexacyanoferrate (II)in potassium nitrate solution; a classical redox couple. The electro-chemical experiment performed was cyclic voltammetry on a rotated disk electrode and voltammetry of vanadium(IV) in sulfuric acid. This is a system relevant to the redox flow battery energy storage system. A rather slow voltammetric scan (1 mV/s), coupled with rapid data collection using the multi-sine impedance function, was successfully used to collect impedance data without distortion caused by the changing voltage bias during the voltammetric scan. While the instrument facilitates collection of the data series as described, it does not have a built in data processing that would allow sequential evaluation of all the impedance data series collected. We have developed such an evaluation routine and we are presenting, for the first time, detailed impedance data results running in parallel with the data for voltammetric measurements. Impedance evaluation usually relies on fitting the data to a suitable equivalent circuit. Attached file is an example shoving variation of one model resistor in the circuit in response to the applied potential. Figure 1

Metal nature effect on catalytic reactions in furfural-H2O2-H2O-group V or VI d-metal salt systems in acid media

Homogeneous catalytic reactions of furfural oxidation by hydrogen peroxide in an aqueous medium in the presence of catalytic amounts of a vanadium, niobium, molybdenum, or chromium salt have been studied to compare them with the acid-autocatalytic reaction. The formation of peroxo complexes of the corresponding metals has been established. The interaction of these peroxo complexes with the carbonyl group of furfural affords organic metal-containing peroxides. The subsequent transformations of these peroxides in the presence of the indicated catalysts lead to different dominant final products. This is explained by different mechanisms of the oxidation of the key intermediates, namely, 2-formyloxy- and 2-hydroxyfurans. In the presence of the vanadium and molybdenum salts, the catalytic role of the resuting carboxylic acids is insignificant, as distinct from what is observed in the acid-autocatalyzed reaction.

Effects of vanadium (III, IV, V)-chlorodipicolinate on glycolysis and antioxidant status in the liver of STZ-induced diabetic rats

Vanadium compounds exert various insulin-mimetic and anti-diabetic effects both in vitro and in vivo. Vanadium(III, IV, V)-chlorodipicolinate (Vdipic-Cl) compounds, including H[VIII(dipic-Cl)2]·5H2O (V3dipic-Cl), VIVO(dipic-Cl)(H2O)2 (V4dipic-Cl) and K[VVO2(dipic-Cl)] (V5dipic-Cl), were synthesized with the indicated oxidation states. The present study was conducted to investigate if chemical valence and anti-oxidation effects of vanadium compounds are involved in the anti-diabetic effects observed in streptozotocin (STZ)-induced diabetic rats treated with these vanadium compounds. V3dipic-Cl, V4dipic-Cl, V5dipic-Cl, inorganic vanadium salts vanadyl sulfate (VOSO4) or sodium metavanadate (NaVO3) were orally administered in drinking water (50μgV/ml) to STZ-induced diabetic rats for 28days. The results showed that Vdipic-Cl treatment significantly improved hyperglycemia and glucose intolerance, as well as increased hepatic glycogen synthesis in diabetic rats. The mRNA levels of key glycolytic enzymes in liver, phosphoenolpyruvate carboxykinase (PEPCK), glucokinase (GK), and L-pyruvate kinase (L-PK) altered in diabetic animals were significantly restored towards normal values by treatment with some of the vanadium compounds. Moreover, the diabetes elevated activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) in serum were significantly decreased after treatment with Vdipic-Cl complexes. Furthermore, treatment of diabetic rats with V4dipic-Cl and V5dipic-Cl compounds significantly reduced malondialdehyde (MDA) production and increased glutathione peroxidase (GSH-Px) and catalase (CAT) activities. These data suggest that vanadium compounds with the indicated chemical valence promote glycogen synthesis and recover suppressed glycolysis in the liver of diabetic rats due to their capacity to reduce oxidative stress by stimulating antioxidant enzymes.

Electrochemical Impedance Spectroscopy – Just One of Many Tools to Study Batteries and Power Sources

Electrochemical Impedance Spectroscopy (EIS) is one of the many methods available to the researcher in electrochemistry. To take full advantage of its capabilities, one should understand the method and the underlying principles. In this work voltammetry on a stationary electrode, as well as with a rotated disk electrode (RDE) are presented together with EIS results, exemplified by reduction and oxidation of vanadium salts in 3 mol/l sulfuric acid. This contribution summarizes highlights, but also pitfalls of impedance measurements and their interpretation, as they are relevant to the practice and theory of electrochemical work. The most significant component in the equivalent circuit is the change transfer resistance, which matches well the voltammetric curves of the RDE experiment. A high-frequency artifact can be eliminated by formally fitting it to an inductor and resistor of series; both of these components have, however, negative value.

The vanadium compounds: chemistry, synthesis, insulinomimetic properties

The review considers the biological role of vanadium, its participation in various processes in humans and other mammals, and the anti-diabetic effect of its compounds. Vanadium salts have persistent hypoglycemic and antihyperlipidemic effects and reduce the probability of secondary complications in animals with experimental diabetes. The review contains a detailed description of all major synthesized vanadium complexes having antidiabetic activity. Currently, vanadium complexes with organic ligands are more effective and safer than the inorganic salts. Despite the proven efficacy of these compounds as the anti-diabetic agents in animal models, only one organic complex of vanadium is currently under the second phase of clinical trials. All of the considered data suggest that vanadium compound are a new promising class of drugs in modern pharmacotherapy of diabetes.