脂肪组织中的钒

人们很少听说钒这个元素 ,主要是因为它在地壳中的存在十分分散 ,冶炼价值不大 ,生产量很少 ,应用也就少了。但是 ,它在地壳中含量却不少 ,甚至比铜、锡、锌还多。因此 ,人体组织中含有微量的钒也就不足为奇了。钒还是人体必需的微量元素 ,只是发现并认识它对健康有益还只是十来年前的事。在人体组织中微量的钒 ,主要存在脂肪中。目前 ,已知钒的生理功能主要有 :抑制胆固醇的合成 ;增强牙釉质的硬度 ,减少龋齿病发病率 ;加强单胺氧化酶的活性 ,降低血压 ;促进硫的代谢。成年人每日的钒需要量约为 1～ 3微克。人体缺钒可以多进食海参等海生动…     

溴酸钾-RB体系催化动力学光度法测定痕量钒

钒是人体不可缺少的微量元素之一,人体中钒含量过高或过低都会影响人体的新陈代谢,从而引起不适应症状甚至病变。钒主要存在于岩石矿物中,钢铁、淤泥、废水、食品甚至于人的头发中也含有微量钒。目前,钒的测定主要有光度法[1]、荧光法[2]、化学发光法[3]、极谱法[4]、色谱法[5]     

催化荧光法测定人发中痕量钒

钒是人体必须微量元素之一,适量的钒有助于人体健康,由于人体中钒含量极微,选择快速灵敏、选择性好的测定方法,很有必要。催化荧光动力学分析法具有灵敏度高、选择性好的显著特点,近年来用于测钒的报道不少。作者发现,在稀硫酸介质中,以柠檬酸为活化剂,痕量钒（Ⅴ）对溴酸钾氧化二氯荧光素的反应具有很强的催化作用,能使二氯荧光素的荧光强度减小。本文主要研究了该反应的动力学条件,共存离子的影响及人发样中痕量钒的测定,建立了催化荧光法测定痕量钒的方法。     

贵州三穗县钒矿石及矿渣微量元素综合利用评价

目的：探讨钒矿及矿渣中的微量元素含量,以便为钒矿石和矿渣的有效利用提供重要参考。方法采用ICP-MS对钒矿石中的微量元素进行分析,并对钒矿石和矿渣中的微量元素利用进行了评价。结果钒矿中的钒利用率仅为64.9％,矿渣中的V、 Cr、 Zn、 Mo、 Cd和U的含量很高。结论分析认为, V、 Cr、 Zn、 Mo、 Cd和U可能会对环境造成一定的影响。     

不平“钒”的金属元素*

钒是地壳中含量第21丰富元素,是人体必需的微量元素。介绍钒元素的发现、自然分布以及在人体内的循环。重点从化学结构分析钒酸盐磷酸盐的拮抗作用机制,从生化机理阐述钒化合物对激酶与磷酸酶的调节、对RNA和DNA功能的影响、对活性氧作用的影响,从人体健康视角探讨钒对治疗糖尿病和癌症及保护心血管等的潜在药理学作用。     

柠檬酸-孔雀石绿系统催化动力学光度法测定痕量钒

钒是一种重要的微量元素[1,2],是人体不可缺少的微量元素之一.适量的钒有利于身体健康,但含量过多或过少都会引起某些器官的病变.同时,钒的类胰岛素作用使得生命有机体中钒的生化机理研究和开发治疗糖尿病钒口服药成为当前钒化学研究热点之一.另外,钒可以改善钢的性能,能增强钢的强度、弹性以及抗磨损和抗爆裂性,并且能耐高温又能抗奇寒.钒的氧化物已成为化学工业中最佳催化剂之一,有"化学面包"之称.因此,寻求一种对痕量钒准确检测的方法具有十分重要的意义.     

萃取法无火焰原子吸收测尿中痕量钒

钒是重要合金材料,又是催化剂,在石油中亦有一定数量的钒。以瑞典一家火电厂为例,它每小时耗重油20—30吨,有20—30公斤V_2O_5随之排入环境。钒的环境污染已日益引起人们的关注。钒已被证实为人体必需微量元素之一,上野清一介绍,人尿中含钒量在1μg1~(-1)以下,甚至低于0.1μg1~(-1),这就要求钒的生物监测必须达到亚ppb级水平。     

二苯碳酰二肼光度法测定微量铬的改进

正以六价铬和三价铬价态存在的铬,在地壳中的含量排序稍靠前,属于自然界中分布较普遍的化学元素之一。其中三价铬参与协作生物体内葡萄糖平衡及脂肪、蛋白质的代谢作用,是人体新陈代谢必不可少的微量元素,但人体或动植物摄入过多的三价铬会对机体产生伤害;毒性较大、对人体表皮肌肤有刺激、有高致癌特性的六价铬更易被人体所吸收,在体内产生蓄积,污染环境又影响人体健康,因此铬是环境监测中的重要监控项目。目前,测定总铬含量     

钒(Ⅴ)-三溴偶氮胂-溴酸钾催化动力学光度法测定钒

1 引言 钒是人体不可缺少的微量元素之一.适量的钒有利于身体健康,但含量过低或过高都会引起某些器官的病变而出现不适的症状,因而对其准确的测定具有重要的意义.近年来,用催化光度法测定钒引起了人们的广泛兴趣.     

可视滴定法测定铝钒中间合金中的钒时称样量和滴定液浓度的优化

用可视滴定法测定铝钒中间合金中的钒时,对称样量和硫酸亚铁铵滴定液浓度的关系进行了探讨。实验发现,基体铝对于铝钒合金中钒的测定无影响。常见的铝钒合金范围为50%～60%,低于50%和高于标准上限0.5%钒含量的合金没有实验样品,通过向样品溶液中加入钒标准溶液可模拟铝钒合金试样。依据化学分析等物质量反应定律,选择不同钒含量的试验样品,对钒的称样量和滴定液浓度进行优化,确定了硫酸亚铁铵滴定液的浓度与滴定液消耗体积的合适关系。     

Determination of beryllium,barium, vanadium and some other elements in water by atomic absorption spectrometry with electrothermal atomization

The determination of beryllium, barium and vanadium by atomic absorption spectrometry in an uncoated graphite furnace poses several problems, e.g. bad reproducibility, memory effects, etc. These difficulties can be avoided by using tubes coated with pyrolytic graphite and carbide. The optimal temperature for the pyrolytic graphite coating and the quantity of lanthanum that should be introduced for the carbide coating are discussed. Beryllium, barium and vanadium in surface water and tap water can be determined without memory effects and with detection limits of 0.01, 1 and 1μg l^-1, respectively. Good agreement was found with the results obtained by activation analysis and flame or flameless (with uncoated tubes) atomic absorption spectrometry after preconcentration. The lifetime of the coated tubes was increased, and improved results were also found for the determination of other carbide-forming and/or high-melting elements such as molybdenum, cobalt, nickel, copper and chromium.     

Interaction of dipicolinatodioxovanadium(V) with polyatomic cations and surfaces in reverse micelles

In confined media such as reverse micelles, molecular probes frequently reside at and interact strongly with the interface. If the interface is charged, it is often difficult to separate effects arising from interactions with the charged species from the effect of the interfacial environment. With reverse micelles as a model system, the work reported here explores the interaction of the charged surfactant headgroups at a self-assembled interface with the dipicolinatodioxovanadium(V) coordination complex. The vanadium complex studied in these experiments serves as an excellent probe to investigate how charged metal complexes interact with lipid interfaces. For comparison, measurements were also carried out probing the interaction of the vanadium complex with a model cationic headgroup, tetramethylammonium bromide. The impact of the environment is gauged by changes in the 51V chemical shift, longitudinal relaxation times, and 1H NMR pulsed field gradient measurements. These measurements suggest that while interface component parts, as modeled by the dispersed systems, interact with the vanadium complex, the interfacial environment perturbs the complex substantially more strongly than the sum of the components alone. Coulomb attraction dominates the interaction in all systems probed and surprisingly orients the hydrophobic portion into the bulk water.     

La détermination du vanadium par la méthode spectrophotométrique en solution non-aqueuse

On mixing small quantities of an aqueous solution of vanadium, containing hydrogen peroxide and acidified with HCl, with anhydrous dioxan containing gaseous hydrogen chloride in molar concentration, an intense red-yellow colour appears, in the presence of as little as 5 μg/ml vanadium.If a drop of salicylic aldehyde is added to the solution thus obtained, the colour changes to violet-blue, which shows an absorption maximum at 565 mμ, clearly visible even with 1 μg/ml vanadium.This reaction, though a sensitive method for the detection of vanadium, is not suitable for quantitative measurement of this substance because the small quantity of water introduced in the form of the vanadium solution hydrolyses the coloured compounds.Very good results can be obtained by dissolving the dry residue (at 100°C) of the solution under examination in 0.2 ml of N HCl in 2% aqueous H₂O₂ solution, and then in 5 ml of a solution made up of 40% acetic anhydride containing gaseous HCl (1 N), 40% glacial acetic acid, and 20% methyl Salicylate.By this method as little as 1 μg of vanadium can be determined.Co, Mo, and W, interfere; the other elements do not.     

Determination of trace vanadium in natural waters by a combined ion exchange—catalytic photometric method

A sensitive, selective and simple method is described for the determination of trace vanadium in natural waters. Vanadium is separated and concentrated by a combined cation- and anion-exchange procedure in 0.05 M HCl—0.1 % H₂O₂ media, and determined by the catalytic method based on the oxidation of gallic acid by bromate. The proposed method is applied to the analysis of natural waters. The relative standard deviations are 3.9 % for 0.8 p.p.b. of vanadium in river water and 3.2 % for 1.9 p.p.b. of vanadium in lake water (surface). As little as 0.03 p.p.b. of vanadium can be determined in samples of 100 ml or less.     

Water transport study across commercial ion exchange membranes in the vanadium redox flow battery

The water transfer behaviour of Selemion CMV, AMV and DMV membranes (Asahi Glass, Japan) has been studied in the vanadium redox cell, as was the water transfer across Nafion 117 membrane (E.I. Du Pont, USA). The earlier water transport studies of a variety of commercial ion exchange membranes and non-ionic separators in the vanadium redox cell have shown that the net water transport through anion exchange membranes and non-ionic separators in the vanadium redox cell is from the positive half cell (+ve) to the negative half cell (−ve), while for cation exchange membranes the net water transport is in the opposite direction. In the present study, it was found that a significant amount of water is transferred across cation exchange membranes from the −ve vanadium half cell electrolyte to the +ve vanadium half cell electrolyte by the hydration shells of V²⁺ and V³⁺ ions which carry a large amount of water and can easily permeate through cation exchange membranes due to their relatively high charge numbers. The net amount of water of hydration which is transferred across anion exchange membranes from the −ve half cell electrolyte, however, is almost equal to the net amount of water of hydration which is transferred from the +ve half cell electrolyte. Thus, the net amount of water which is transferred across anion exchange membranes is in the same direction as the osmotic water transfer.     

Atomic-absorption determination of vanadium and molybdenum in tap water and mineral waters after anion-exchange separation.

A method is described for the determination of vanadium and molybdenum in samples of tap and bottled mineral water. After acidification with citric acid the water sample is heated to about 80°C to remove CO₂; sodium citrate and ascorbic acid are added and the resulting solution of pH 3 is passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (citrate form) on which both vanadium and molybdenum are adsorbed as anionic citrate complexes. Vanadium is eluted with 6 M hydrochloric acid; molybdenum is recovered with 2 M perchloric acid-1 M hydrochloric acid. Vanadium and molybdenum are determined in the eluates by atomic-absorption spectrometry. The samples analysed contained 0.1–0.9 μg l^?1 vanadium and 0.2–13 μg l^?1 molybdenum.     

全钒液流电池储能技术开发与应用进展

大规模储能技术是实现大规模可再生能源普及应用和支撑智能电网建设的核心技术. 全钒液流电池（Vanadium Flow Battery, VFB）因其寿命长、安全性好、配置灵活、响应速度快、建设周期短、对环境影响低等突出优势,成为大规模电化学储能技术的首选. 美、日、欧等发达国家都在积极推动大型全钒液流电池技术和装备的研发. 本文重点介绍了由大连融科储能技术发展有限公司和中科院大连化学物理研究所开发的集装箱式全钒液流电池系统的测试结果,对迄今全球最大规模的5 MW/10 MWh全钒液流电池系统的运行情况进行了总结,最后指出通过进一步技术开发与规模化生产,降低其成本、提高其可靠性和电化学性能,是全钒液流电池技术和产业发展的主要方向.     

Vanadium in Italian waters: monitoring and speciation of V(IV) and V(V)

In this work, a highly sensitive method was developed to separate vanadium (IV) from vanadium (V), which are both contained in water at trace levels. A suitable strong anionic exchange column (SAX) loaded with disodium ethylendiaminetetraacetic acid (Na₂EDTA) was used to trap both vanadium species dissolved in 10–100 ml of water at pH 3. The vanadyl ion was selectively eluted by means of 15 ml of an aqueous solution containing Na₂EDTA, tetrabutylammonium hydroxide (TBA⁺OH⁻), and isopropanol (ⁱPr-OH) and was subsequently determined by atomic absorption spectroscopy with electrothermal atomization. The concentration of vanadate ion was calculated by subtracting the vanadyl concentration from the total concentration of vanadium. The optimal conditions for a selective elution were evaluated. The recovery of vanadium (IV) was 95% or better. The proposed method provides a simple procedure for the speciation of vanadium in aqueous matrices. The collection of the two forms could easily be carried out at the sampling site. Therefore, the risk of changing the concentration ratio between vanadium species was widely reduced. The detection limits were 1 μg/l for both species, when a 10-ml sample was eluted through the column. The method was applied successfully to vanadium speciation on different kinds of Italian volcanic water: Mount Etna (Sicily), Lake Bracciano and Castelli Romani (Latium).     

51V magic angle spinning NMR spectroscopy of six-coordinate Lindqvist oxoanions: a sensitive probe for the electronic environment in vanadium-containing polyoxometalates. Counterions dictate the 51V fine structure constants in polyoxometalate solids

Geometric and electronic environments of vanadium have been addressed by (51)V magic angle spinning NMR spectroscopy of six-coordinated polyoxometalate solids. (C(4)H(9))(4)N(+) and mixed Na(+)/Cs(+) salts of the Lindqvist-type mono- and divanadium-substituted oxotungstates, [VW(5)O(19)](3-) and [V(2)W(4)O(19)](4-), have been prepared as microcrystalline and crystalline solids. The solid-state NMR spectra reflect the details of the local environment of the vanadium site in these hexametalate solids via the anisotropic quadrupolar and chemical shielding interactions. Remarkably, these (51)V fine structure constants in the solid state are dictated by the nature and geometry of the countercations. Electrostatic calculations of the electric field gradients at the vanadium atoms have been performed. Experimental trends are well reproduced with the simple electrostatic model, and explain the sensitivity of the anisotropic NMR parameters to the changes in the cationic environment at the vanadium site.     

Elimination of the interferences of anions in the kinetic spectrophotometric determination of vanadium (V) solution

Accurate determination of vanadium (V) in industrial waste water is of great importance in environmental, biological and toxicological studies. Most of kinetic spectrophotometric methods based on the catalytic effect of vanadium (V), when applied to real samples for determination of trace levels of vanadium (V) lack the satisfactory sensitivity and selectivity. This may be attributed to the serious interferences of various anions which are common pollutants in industrial waste water. The oxidation of gallic acid by ammonium persulphate, catalysed by vanadium (V) was chosen for our study. The effect of the serious interferences of various anions such as chloride, bromate, bromide, chromate, iodide, iodate, molybdate, carbonate and sulphate on the net absorbance given by 4 microg l(-1) of vanadium (V) solution were studied. The minimum concentrations of citric acid, EDTA, ascorbic acid and oxalic acid as leveling off agents required to level off interfering effects due to the aforementioned anions in the kinetic determination of vanadium (V) were 50, 70, 80 and 120 microg ml(-1), respectively. In the presence of optimum concentrations of effective leveling off agents, the dynamic range can be extended and sensitivity increased as compared with the proposed method without levelling off agents. The proposed method is a rapid, sensitive and selective method for the determination of ultra trace amounts of vanadium (V) in real samples with satisfactory results.