Determination of Vanadium in Tissues By Atomic Absorption Spectrophotometry

Abstract

A simple and sensitive method for the determination of vanadium in tissues was established by using atomic absorption spectrophotometry with graphite furnace atomisation. The proposed method includes formation of a chelate-complex by reacting vanadium with pyrrolidine dithiocarbamate (PDCA), extracting the chelate with xylene and measurement of the extract using atomic absorption spectrometry. The recoveries of added vanadium in various rat tissues were 96.7 and 109.3%, within 8.6% of the coefficient variation. The sensitivity of this method is 10 – 50 times higher than previous methods, the detection limit is 0.01 μg/g.     

Determination of submicrogram amounts of vanadium in biological materials by extraction with N-cinnamoyl-N-2,3-xylylhydroxylamine and flameless atomic-absorption spectrometry with an atomizer coated with pyrolytic graphite

A highly sensitive and simple method for determination of vanadium in plants and biological samples by solvent extraction and flameless atomic-absorption spectrometry with a carbon tube coated with pyrolytic graphite is described. After digestion of the sample, vanadium is separated by extraction of its N-cinnamoyl-N-2,3-xylylhydroxylamine complex into carbon tetrachloride from 6M hydrochloric acid medium. The method can be used to determine vanadium in plants and biological samples with average recovery of 94% and coefficient of variation of 14%. The sensitivity (1% absorption) is estimated to be 4 x 10(-11) g.     

Trace Analysis of Vanadium in Environment as its Ternary Complex with N-p Methoxyphenyl-2-Furylacrylohydroxamic Acid and 3-(o-Carboxyphenyl)-1-Phenyltriazine-N-Oxide

Abstract

A method is presented for the highly sensitive, selective, and rapid determination of vanadium (V) at sub-microgram levels in rocks, animal tissues, plant tissues and natural waters. The method is based on the selective extraction of vanadium (V) from strongly acidic (3-8 M hydrochloric acid) medium with solution of N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA) in chloroform. The reddish-violet extract (molar absorbance 8.6x10³ 1 mole^?1 cm^?1 at λ max 545 nm) is then equilibrated with 3-(o-carboxyphenyl)-1-phenyltriazine-N-oxide (CPPTNO) at pH = 1.5. The resulting ternary complex has enhanced colour (molar absorbance 1.4 × 10⁴ 1 mole^?1 cm^?1 at Λ max 450 nm). The ternary system obeys Beer's Law at 450 nm over the range 0-18 μ g/ml of vanadium. The extraction system achieves 20-fold enrichment of vanadium and enables the determination of the metal down to parts per billion (ng 1^?1) levels. The method tolerates the presence of a large number of anions and cations which are normally present with vanadium in rocks, plant tissues, animal tissues and natural waters. The applicability of the method was tested by the analysis of vanadium in these matrices. MFHA was selected from nine hydroxamic acids as it provided maximum sensitivity and selectivity.     

Novel catalytic effects of Mn3O4 for all vanadium redox flow batteries

A new approach for enhancing the electrochemical performance of carbon felt electrodes by employing non-precious metal oxides is designed. The outstanding electro-catalytic activity and mechanical stability of Mn(3)O(4) are advantageous in facilitating the redox reaction of vanadium ions, leading to efficient operation of a vanadium redox flow battery.     

Determination of vanadium in serum by pre-irradiation and post-irradiation chemistry and neutron activation analysis

Vanadium in serum was investigated by pre-irradiation chemistry neutron activation analysis employing anion exchange chromatography and post-irradiation neutron activation employing solvent extraction techniques. From a comparison of these techniques it is concluded that vanadium is present in human serum in the sub-ppb range.     

Direct Determination of Vanadium in Water Samples,Human Hairs,Vegetables, and Foods by Graphite Furnace Atomic Absorption Spectroscopy

At present,the considerable attention was greatly paid to the determination of vanadium from the point of vanadium as a kind of biological nutrient element or one kind of industrial sources of pollution. In the paper,we employed graphite furnace AAS (GFAAS) method to determine directly the vanadium in samples, using optically controlled raising temperature combining with pyrolytic coating tube to atomize vanadium under the conditions of stable temperature for the determination of vanadium in samples.     

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.     

钒酰腙配合物的合成、结构及生物活性

以酰腙为配体钒的单核、双核配合物因其结构丰富、生物活性多样而引起广泛关注。目前该领域新配合物的合成、表征和生物活性的研究甚为活跃。本文回顾了近年来钒酰腙配合物的研究状况,主要从以下三个方面进行综述：(1)钒酰腙配合物的合成方法;(2)此类配合物的配位模式;(3)一些单、双核钒酰腙配合物抗变形虫,抗肿瘤,类胰岛素,抑制Na⁺, K⁺-ATP酶,与DNA作用的生物活性。文中着重阐述了钒酰腙化合物的结构和生物活性之间的关系。此外,还提出了钒酰腙配合物研究领域的不足之处并对其今后发展方向进行了展望。     

Application of HPLC to measure vanadium in environmental,biological and clinical matrices

Vanadate and vanadium compounds exist in many environmental, biological and clinical matrices, and despite the need only limited progress has been made on the analysis of vanadium compounds. The vanadium coordination chemistry of different oxidation states is known, and the result of the characterization and speciation analysis depends on the subsequent chemistry and the methods of analysis. Many studies have used a range of methods for the characterization and determination of metal ions in a variety of materials. One successful technique is high performance liquid chromatography (HPLC) that has been used mainly for measuring total vanadium level and metal speciation. Some cases have been reported where complexes of different oxidation states of vanadium have been separated by HPLC. Specifically reversed phase (RP) HPLC has frequently been used for the measurement of vanadium. Other HPLC methods such as normal phase, anion-exchange, cation-exchange, size exclusion and other RP-HPLC modes such as, ion-pair and micellar have been used to separate selected vanadium compounds. We will present a review that summarizes and critically analyzes the reported methods for analysis of vanadium salts and vanadium compounds in different sample matrices. We will compare various HPLC methods and modes including sample preparation, chelating reagents, mobile phase and detection methods. The comparison will allow us to identify the best analytical HPLC method and mode for measuring vanadium levels and what information such methods provide with regard to speciation and quantitation of the vanadium compounds.     

Spectrophotometric determination of vanadium in biological materials with N-benzylbenzohydroxamic acid

A spectrophotometric method for the determination of vanadium in biological materials with N-benzylbenzohydroxamic acid is proposed. The method is highly selective for vanadium and is free from rigid control of reaction conditions. No separation of iron prior to the determination of vanadium is necessary. Cu(II), Co(II), Ni, Mn(II), Cr(III), Ce(IV), Zr, Mo(VI), Ca, Sr, Ba, UO(2)(II) and many others metal ions do not interfere. Fairly large quantities of Ti(IV) and W(VI) are tolerated.     

Trends in speciation analysis of vanadium in environmental samples and biological fluids--a review

A comprehensive review is presented addressing recent trends in the speciation and determination of vanadium in environmental and biological sample matrices, including important analytical aspects such as sample clean up, pre-concentration and method development. Methodology based on both separation and spectroscopic techniques for the determination of vanadium speciation is discussed. A brief outline of analytical principles, together with an overview of the recent developments and applications of vanadium speciation determination is included. The newer methods for detecting metal ions including hyphenated spectroscopic techniques and sample preparation schemes are also discussed.     

n-arylhydroxamic acids as reagents for vanadium(v) : Spectrophotometric determination of vanadium(v) with n-m-tolyl-p-methoxybenzohydroxamic acid

A study of the coloured complexes of 51 N-arylhydroxamic acids with vanadium(V) in hydrochloric acid media is described. The absorption spectra of the coloured chloroform extracts and the molar absorptivities are compared. The effects of different substituents attached to the carbon and nitrogen atom of the hydroxamic acid functional group are discussed. A rapid extraction-spectrophotometric method for the determination of vanadium(V) is described, employing the most promising of these reagents, N-m-tolyl-p-methoxybenzohydroxamic acid. The method is highly selective and tolerates large amounts of diverse ions usually associated with vanadium-bearing materials including iron(III), aluminium(III), chromium(III), nickel(II), cobalt(II), zinc(II) and manganese(II).     

Spectrophotometric determination of vanadium using variamine blue and its application to synthetic, environmental and biological samples

A simple, rapid and accurate spectrophotometric method is described for the determination of trace amounts of vanadium using variamine blue (VB) as a chromogenic reagent. The method is based on the oxidation of variamine blue to form a violetcolored species on reaction with vanadium(V), having an absorption maximum at 570 nm. Beer’s law is obeyed in the range of 0.1–2.0 μg ml^?1. The molar absorptivity and Sandell’s sensitivity were found to be 1.65 × 10⁴ l mol^?1 cm^?1 and 0.003 μg cm^?2, respectively. Optimum reaction conditions were evaluated in order to delimit the linear range. The effect of interfering ions on the determination is described. The proposed method has been successfully applied to the determination of vanadium in steel, pharmaceutical, environmental, and biological samples.     

Supervanadophile: Complexation, preconcentration and transport studies of vanadium by octa functionalized calix[4]resorcinarene-hydroxamic acid

A new octa functionalized calix[4]resorcinarene bearing eight hydroxamic acid groups (OFCHA) has been synthesized and its analytical properties have been investigated. To elucidate the structure of the compound, elemental analysis, FT-IR and ¹H NMR spectral data have been used. The compound showed high affinity and selectivity for vanadium(V) in presence of large quantities of associated metal ions. The complexation of vanadium(V) with OFCHA has a 4:1 metal: ligand stoichiometry as evaluated by Job’s plot. A spectrophotometric method is proposed for the extractive determination of vanadium(V) in an acidic medium in the presence of diversified matrix, and verified by ICP-AES. Under the optimum condition of acidity, solvent, interfering ions and OFCHA concentration, the molar absorptivity of the complex is 5630 l mol^-1 cm^-1 at 495 nm. The system obeys Beer’s law over the range 0.125–8.75 μg ml^-1 of vanadium(V) with Sandell sensitivity 0.009 μg cm^-2. The preconcentration factor and overall stability constant evaluated at 25 °C were 142 and 14.18, respectively. The complexation is characterized by favorable enthalpy and entropy changes. Liquid membrane transport studies of vanadium(V) were carried out from source to the receiving phase under controlled conditions and a mechanism for transport is suggested. To check the validity of the proposed method, vanadium is determined in environmental, biological samples and some standard reference materials from NIST and BCS.     

Preparation and characterization of vanadium(IV) oxide supported on SBA-15 and its catalytic performance in benzene hydroxylation to phenol using molecular oxygen

Preparation of dispersed transition metal oxides catalyst with low oxidation state still remains a challenging task in heterogeneous catalysis.In this study,vanadium oxides supported on zeolite SBA-15 have been prepared under hydrothermal condition using V 2 O 5 and oxalic acid as sources of vanadium and reductant,respectively.The structures of samples,especially the oxidation state of vanadium,and the surface distribution of vanadium oxide species,have been thoroughly characterized using various techniques,including N 2-physisorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),UV-visible spectra(UV-Vis) and UV-visible-near infrared spectra(UV-Vis-NIR).It is found that the majority of supported vanadium was in the form of vanadium(IV) oxide species with the low valence of vanadium.By adjusting hydrothermal treatment time,the surface distribution of vanadium(IV) oxide species can be tuned from vanadium(IV) oxide cluster to crystallites.These materials have been tested in the hydroxylation of benzene to phenol in liquid-phase with molecular oxygen in the absence of reductant.The catalyst exhibits high selectivity for phenol(61%) at benzene conversion of 4.6%,which is a relatively good result in comparison with other studies employing molecular oxygen as the oxidant.     

Determination of vanadium species in environmental samples

The distribution of vanadium between different oxidation states plays an important role in its environmental chemistry. As its two most commons forms, vanadium(IV) and vanadium(V) have different toxicity, speciation analysis of this element is necessary for environmental and biological samples. This paper presents recent research on the determination of vanadium species. Some important problems concerning stability of vanadium forms and proposed separation techniques are discussed.     

基于甘露糖功能化的水凝胶用于E.coli O157: H7的检测

利用伴刀豆球蛋白A(Con A)的多价结合能力, 结合水凝胶技术与核酸染色技术发展了一种基于甘露糖功能化的水凝胶检测大肠杆菌(E.coli)O157: H7的方法. 以过硫酸铵(APS)为催化剂, 四甲基乙二胺(TEMED)为加速剂, 用丙烯酰胺(AAm)、N,N-二甲基双丙烯酰胺和N-丙烯酰氧琥珀酰亚胺(NAS)合成水凝胶, 通过氨基化甘露糖与NAS发生交联反应, 制备了甘露糖功能化的水凝胶. 当甘露糖功能化的水凝胶加入与Con A共孵育后的菌悬液中时, 由于Con A既能与甘露糖特异性结合, 又能与E.coli O157: H7表面的O-抗原发生免疫反应而紧密连接, 使目标菌被捕获到水凝胶表面, 采用核酸染料SYBR Green Ⅰ对捕获细菌进行染色, 实现了对E.coli O157: H7的核酸标记, 最后通过活体荧光成像系统对水凝胶进行荧光成像, 从而实现对待测样品的检测. 研究结果表明, 该方法可应用于缓冲液体系和混合细菌样品中E.coli O157: H7的特异性检测, 且整个检测步骤包括样品预处理可在2 h内完成. 该方法成本低、易操作, 且具有较好的灵敏度, 可检出3.7×10¹ Cells/mL的目标细菌样品.     

从钒化合物生物效应的多样性看其作用机制*

本文对近年来关于钒化合物不同生物效应机制的研究进展进行了总结,着重于其类胰岛素和抗癌效应的信号转导机制以及两者之间的相关性。同时,基于钒化合物对磷酸转移反应的干预以及对细胞氧化还原状态的调节,讨论了钒化合物多样化的生物效应是否具有一个共同作用机制的可能性,并提出了未来钒化合物研究方向和所面临的挑战。     

An oxidative cross-dehydrogenative-coupling reaction in water using molecular oxygen as the oxidant: vanadium catalyzed indolation of tetrahydroisoquinolines

An aerobic oxidative cross-dehydrogenative coupling reaction between sp(3) C-H and sp(2) C-H bonds is developed by employing a vanadium catalyst (10 mol%) in an aqueous medium using molecular oxygen as the oxidant. This environmentally benign strategy exhibits larger substrate scope and shows high regioselectivity.