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1.
在酸性介质条件下,钒(Ⅳ)能显著催化溴酸钾对二甲酚橙的氧化褪色反应。据此建立了测定痕量钒(Ⅳ)的顺序注射催化光度法。方法的线性范围为0.550ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%50ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%108%。 相似文献
2.
在酸性介质条件下,钒(Ⅳ)能显著催化溴酸钾对二甲酚橙的氧化褪色反应。据此建立了测定痕量钒(Ⅳ)的顺序注射催化光度法。方法的线性范围为0.5~50ng/mL、检出限为0.4ng/mL。对10ng/mL的钒(Ⅳ)连续11次测定的相对标准偏差为1.1%。用于环境水样中痕量钒(Ⅳ)的测定,加标回收率为91%~108%。 相似文献
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正在全钒氧化还原液流电池体系中,钒储能介质既是能量转换介质更是能量储存的载体,是电池的核心组成之一。钒(Ⅱ)极易被空气氧化,钒(Ⅴ)只能通过电解氧化获得,而且不稳定、易析出~[1],因此通常不以钒(Ⅱ)或钒(Ⅴ)的状态生产、存储钒储能介质;钒(Ⅲ)和钒(Ⅳ)易生产获得,而且稳定性好,所以钒储能介质的初始状态通常为钒(Ⅲ)、钒(Ⅳ)的混合状态,理论上正、负极钒储能介质的初始综合价态为 相似文献
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杨梅型高分子载体催化剂的研究I.聚羧酸氧钒-硫脲引发丙烯腈聚合动力学 总被引:3,自引:0,他引:3
使用了一种有特殊形态结构的均相化非均相催化剂——杨梅型聚羧酸氧钒(Ⅳ)(PV)与硫脲(TU)组成的氧化还原体系,引发硝酸溶液中丙烯腈(AN)的聚合反应。在实验条件下,得到表现聚合速度的关系式如式(1)。PV(Ⅳ)-TU体系引发丙烯腈和丙烯酸甲酯(MA)共聚合的结果,表明反应按自由基机理进行。 硫酸氧钒(Ⅳ)与硫脲的组合不能引发丙烯腈聚合,但杨梅型聚羧酸氧钒(Ⅳ)在羧基配位体的协同作用下,极容易通过络合物内部的电子转移被氧化成五价钒而有较高的引发活性。这一氧化过程被大分子链效应所促进。大分子链的空间阻碍使链终止反应遵循双分子历程而不是通过向钒(Ⅴ)转移的方式进行。这些异常的行为从硫酸氧钒(Ⅳ)、异丁酸氧钒(Ⅳ)和聚甲基丙烯酸氧钒(Ⅳ)的模拟试验,以及VO_2~+-TU氧化还原体系引发硝酸溶液中丙烯腈聚合动力学的研究结果所证实。 相似文献
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分别以不同的异羟肟酸为配体,合成了3个氧钒(Ⅳ)配合物,运用元素分析、红外光谱、核磁共振谱(^1H NNR,^13C NMR,^51V NMR)、电子顺磁共振和电子吸收光谱等测试手段对配合物进行了表征.分别在不同的羟基醇中以氧钒(Ⅳ)配合物阱BHAOV为基础,合成了2个含烷氧基的五价氧钒(Ⅴ)化合物.在吡啶中合成了含吡啶的六配位氧钒(Ⅳ)配合物阱BHAOV(PY),Ⅴ占据第6位置S原子,可使其不被氧原子进攻而氧化,要使Ⅴ内层发生氧化,在四价钒上至少有一个空的配位位点是完全必要的.而且还研究了BHAOV在乙腈中的配位反应动力学. 相似文献
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应用改进的磷钨酸光度法测定了样品中总钒和钒(Ⅳ)。在10%HCl介质中,一定体积的待测溶液中添加10%(V:V)H_3PO_4和20%(V:V)的Na_2WO_4·2H_2O(50 g/L)溶液,于30℃下显色30 min。方法的线性范围是0~30 mg/L,线性相关系数R^2=0.9992,相对标准偏差(n=12)为1.2%。并确定了天然水溶液中常见离子干扰钒测定的最大允许量。在此基础上,调节溶液的pH>4,测定V(Ⅳ)。改进后方法测V(Ⅳ)的线性范围为0~5 mg/L,相关系数R^2=0.9998。应用测定自来水和河水中V(Ⅳ)。 相似文献
11.
J. M. Bosque-Sendra Ma_ Carmen Valencia Said Boudra 《Analytical and bioanalytical chemistry》1998,360(1):31-37
The separation and preconcentration of vanadium (IV) and vanadium (V) using Sephadex DEAE A-25 with Eriochrome Cyanine R has been studied, based on the preconcentration of vanadium (IV) in the first step and V(V) after reduction with ascorbic acid in the second step. Factors affecting the optimum fixation of the complex were investigated. The absorbance of the solid phase is measured directly at 563 nm for V(IV), at 585 nm for V(V) and at 750 nm for both. The proposed method provides a simple and specific procedure for the separation of vanadium in natural waters. The calibration graph is linear up to 150 ng/mL, with RSD of 4.7% for V(IV) and 4.0% for V(V). The detection limits are 1.6 and 1.4 ng/mL for V(IV) and V(V), respectively. 相似文献
12.
《Spectrochimica Acta Part B: Atomic Spectroscopy》2005,60(1):65-71
A sensitive and simple method for low temperature electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) determination of V(IV) and V(V) after separation/preconcentration by a micro-column packed with immobilized thenoyltrifluoroacetone (TTA) on microcrystalline naphthalene has been developed. Thenoyltrifluoroacetone was used as both a chelating agent for micro-column separation/preconcentration and a chemical modifier for ETV-ICP-OES determination of vanadium. Both vanadium species could be trapped by micro-column at pH 4.0, and the vanadate (VO2+) ion could be collected selectively at pH 2.4. Solid material loaded with analyte in the micro-column was dissolved with 100 μL of acetone containing 2.0 mmol L−1 TTA and the vanadium was determined subsequently by ETV-ICP-OES. The concentration of vanadyl (VO2+) ion was calculated by subtracting the vanadate concentration from the total concentration of vanadium. Under the optimized experimental conditions, the detection limit (3σ) for the preconcentration of 5 mL of aqueous solution is 0.068 μg L−1 for both species and the relative standard deviations were 4.3% for vanadium(V) and 4.8% for vanadium(IV) (c=10 μg L−1, n=7), respectively. The method was applied successfully to the determination of vanadium(IV) and vanadium(V) in natural water samples. 相似文献
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For separation and determination of vanadium(IV/V) species, a fast and sensitive method by combining hollow-fibre liquid phase microextraction (HF-LPME) with electrothermal vaporization (ETV)-ICP-OES has been developed. Two vanadium species (V(IV) and V(V)) were separated by HF-LPME with the use of ammonium pyrrolidinecarbodithioate (APDC) as chelating agent for complexing with different V species and carbon tetrachloride as the extraction solvent, and the vanadium in the post-extraction organic phase was injected into the graphite furnace for ETV-ICP-OES detection, in which APDC was acted as the chemical modifier. At pH 5.0, both V(IV)-APDC and V(V)-APDC were extracted quantitatively into CCl4 for determination of total V. For speciation studies, 1,2-cyclohexanediaminetetraacetic acid (CDTA) was added to the sample for masking V(IV), so that only V(V)-APDC was extracted and determined. The concentration of V(IV) was calculated by subtracting the V(V) concentration from the total concentration of V. Under the optimized experimental conditions, the enrichment factor was 74 and the detection limits for V(IV) and V(V) were 86 pg mL−1 and 71 pg mL−1, respectively. The proposed method has been applied to the speciation of V in environmental water samples, and the recovery was in the range of 94%-107%. The results show that V(V) is the dominant existence form in oxygenic water and V(IV) could not been detected. In order to validate the developed procedure, a NIES No.8 vehicle exhaust particulates certified reference material was analyzed, and the results obtained for total vanadium are in good agreement with the certified values. The proposed method is simple, rapid, selective, and sensitive and no oxidation/reduction is required, it is applicable to the speciation of vanadium in environmental samples with the complicated matrix. 相似文献
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J. M. Bosque-Sendra Ma_ Carmen Valencia Said Boudra 《Fresenius' Journal of Analytical Chemistry》1998,360(1):31-37
The separation and preconcentration of vanadium (IV) and vanadium (V) using Sephadex DEAE A-25 with Eriochrome Cyanine R
has been studied, based on the preconcentration of vanadium (IV) in the first step and V(V) after reduction with ascorbic
acid in the second step. Factors affecting the optimum fixation of the complex were investigated. The absorbance of the solid
phase is measured directly at 563 nm for V(IV), at 585 nm for V(V) and at 750 nm for both. The proposed method provides a
simple and specific procedure for the separation of vanadium in natural waters. The calibration graph is linear up to 150
ng/mL, with RSD of 4.7% for V(IV) and 4.0% for V(V). The detection limits are 1.6 and 1.4 ng/mL for V(IV) and V(V), respectively.
Received: 21 November 1996 / Revised: 15 April 1997 / Accepted: 18 April 1997 相似文献
15.
A new on-line method for the separation of vanadium (IV) and vanadium (V) as well as for the removal of ClO+ mass spectral interference on vanadium determination by quadrupole-ICP-MS has been developed. The sample introduction system consists of a modified fused silica capillary coupled to a direct injection nebuliser (DIN), between the solvent delivery system and the ICP. Fused silica capillaries were treated with different anion and cation exchanger reagents and were tested for the retention of Cl− and the separation of vanadium ions at μg l−1 levels. A suitable strong anion exchanger functional group (3-aminopropyltrimethoxy silane) was selected. Chlorine anions were retained in this anionic capillary and the separation between V(IV) and V(V) was possible in the pH range 2–4. The selections of instrumental ICP-MS conditions for the minimisation of the ClO+ interference were carefully considered. Factors affecting the chromatographic separation such as sample pH, sample flow rate, effect of methanol in the mobile phase and length of the capillary for the separation were optimised. The proposed methodology provides a simple and rapid method for vanadium speciation. A relative detection limit of 12 l−1 (i.e. absolute detection limits of 120 pg) for V(IV) based on peak height measurements was obtained. The relative standard deviation for V(IV) was 2.4% for a 10 μl injection (n=6). 相似文献
16.
A spectrophotometric determination of vanadium as vanadium(IV) pyridine thiocyanate is described. The blue complex is formed in acidic aqueous solution and extracted into pyridine-chloroform. Absorbance is measured at 7.40 mμ. The range of best accuracy for 1-cm cells is from about 80 to 240 μg of vanadium per ml, and sensitivity is 0.4 μg of vanadium per cm2 at 7.40 mμ. The vanadium may be present initially as vanadium(IV) or vanadium(V), which is reduced to vanadium(IV) by the large excess of thiocyanate ion added. Several elements interfere in the determination ; a separation procedure involving mercury cathode electrolysis is suggested. 相似文献
17.
Iglesias-González T Sánchez-González C Montes-Bayón M Llopis-González J Sanz-Medel A 《Analytical and bioanalytical chemistry》2012,402(1):277-285
The use of V(IV) complexes as insulin-enhancing agents has been increasing during the last decade. Among them, 3-hydroxy-2-methyl-4-pyrone
and 2-ethyl-3-hydroxy-4-pyrone (maltol and ethyl maltol, respectively) have proven to be especially suitable as ligands for
vanadyl ions. In fact, they have passed phase I and phase II clinical trials, respectively. However, the mechanism through
which those drugs exert their insulin-mimetic properties is still not fully understood. Thus, the aim of this study is to
obtain an integrated picture of the absorption, biodistribution and insulin-mimetic properties of the bis(maltolato)oxovanadium
(IV) (BMOV) in streptozotocin-induced hyperglycaemic rats. For this purpose, BMOV hypoglycaemic properties were evaluated
by monitoring both the circulating glucose and the glycohemoglobin, biomarkers of diabetes mellitus. In both cases, the results
were drug concentration dependent. Using doses of vanadium at 3 mg/day, it was possible to reduce the glycaemia of the diabetic
rats to almost control levels. BMOV absorption experiments have been conducted by intestinal perfusion revealing that approximately
35% of V is absorbed by the intestinal cells. Additionally, the transport of the absorbed vanadium (IV) by serum proteins
was studied. For this purpose, a speciation strategy using high-performance liquid chromatography (HPLC) for separation and
inductively coupled serum mass spectrometry, ICP-MS, for detection has been employed. The obtained HPLC-ICP-MS results, confirmed
by MALDI-MS data, showed evidence that V, administered orally, is uniquely bound to transferrin in rat serum. 相似文献
18.
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. 相似文献
19.
A novel method is proposed for the solvent extraction of niobium(V). A 0.1M solution of Aliquat 336S in xylene quantitatively extracts microgram quantities of niobium(V) from 0.01M ascorbic acid at pH 3.5-6.5. Niobium from the organic phase is stripped with 0.5M nitric acid and determined spectrophotometrically in the aqueous phase as its complex with TAR. The method permits separation of niobium not only from tantalum(V) but also from vanadium(IV), titanium(IV), zirconium(IV), thorium(IV), chromium(III), molybdenum(VI), uranium(VI), iron(III), etc. Niobium from stainless steel was determined with a precision of 0.42%. 相似文献
20.
O. M. Osmolovskaya V. M. Smirnov A. A. Selyutin 《Russian Journal of General Chemistry》2008,78(10):1872-1876
Vanadium(IV) oxide nanolayers on silica surface were prepared for the first time. Samples characterized by different degrees of surface coverage by vanadium(IV)-oxygen groups were studied. Samples containing only vanadium(IV) ions and both vanadium(IV) and vanadium(V) ions were obtained. The size effect on the phase transition parameters was determined by studying magnetic properties of vanadium(IV) oxide nanolayers. The phase transition temperature ranges from 140 to 220 K, depending on surface concentration of vanadium(IV) ions and their environment. 相似文献