The photometric determination of alcohols by means of vanadium oxinate

Vanadium oxinate dissolved in such organic solvents as chloroform and nitrobenzene can be successfully used for the photometric determination of micromolar quantities of various alcohols. The sensitivity depends upon the dielectric constant of the solvent and the concentration of the reagent. Suggestions are made for using the reaction to estimate the relative reactivity of a given alcohol and the steric effect about the alcoholic OH. The reaction can also be used to differentiate alcohol isomers.     

The spectrophotometric determination of vanadium in rocks

Vanadium in rock samples is determined, after alkaline fusion of the sample, by means of its catalytic action on the oxidation of aniline to aniline black by hydrogen peroxide. If necessary, chromium can be easily extracted to prevent interference. The sensitive procedure was applied to standard granite Gi and diabase Wi, and to the C.A.A.S. syenite i ; values of 16, 263 and 86 p.p.m., respectively, were obtained.     

Spectrophotometric determination of vanadium as V(III) oxinate

Vanadium(V) is rapidly reduced by dithionite to V(III) which is extracted as the oxinate into carbon tetrachloride. Vanadium is determined by measuring absorbance of the complex at lambda(max) = 420-425 nm with a sensitivity of 0.004 microg/cm(2) and Beer's law range of 0-7 microg/ml . Several mg of some important elements can be tolerated if they are masked. Molybdenum interferes seriously. The method has been applied to synthetic samples, rutile and ilmenite with satisfactory results. Using ordinary reagents and taking 10 min or less in series for a determination, the method has a sensitivity rarely exceeded by others with a much higher tolerance for other elements.     

氯酸钾体系催化动力学光度法测定痕量钒(Ⅱ)

研究了在0.1 mol/L H3PO4介质中,活化剂抗坏血酸的作用下,V(Ⅴ)催化KClO3氧化甲基红褪色的指示反应,由此建立了一种测定痕量V(Ⅱ)的催化动力学光度新方法。研究了影响该催化褪色反应的因素。方法的线性范围为0.09～7.0 ng/mL,检出限为2.9×10-2 ng/mL。方法用于实际样品的测定。     

催化动力学光度法测定水中痕量钒

基于在H3PO4介质中, 抗坏血酸作活化剂, 100 ℃沸水浴加热的条件下, 痕量钒V(Ⅴ)催化溴酸钾氧化三溴偶氮氯膦(TB-chorophosphonazo)的褪色反应, 建立了新的测定超痕量钒的催化光度法. 该方法对钒测定范围是0～1.0 ng/mL, 检出限为0.133 ng/mL. 实验考察了影响催化反应速率的各种因素, 确定了最佳的实验条件. 实验测定了反应的动力学参数: 表观活化能Ea'=93.80 kJ/mol, 表观速率常数为k'=1.307×10-3 s-1, 建立了催化反应动力学方程. 方法灵敏度高, 选择性好, 直接用于环境水体中痕量钒的测定.     

The spectrophotometric determination of vanadium after extraction as vanadium(III) ferronate by tribenzylamine

Vanadium(III) obtained by dithionite reduction of vanadium(V) can be extracted as its ferron complex with tribenzylamine in chloroform from 0.05 M sulphuric acid. Vanadium (0–5 μg ml^-1) is determined spectrophotometrically at 430 nm with a sensitivity of 0.0028 μg V cm^-2. Al(III), Co(II), Ni(II), Fe(II, III), Hg(II), Si(IV), Be(II), Mg(II), Ca(II), Sr(II), Ba(II), Cr(VI, III), W(VI), Zn(II), U(VI), Mn(II). Pb(II), Cu(II), Cd(II) and Th(IV) do not interfere; only Mo(VI), Ti(IV), Zr(IV). Bi(V) and Sn(II) interfere. A single determination takes only 7 min. The extracted complex is V^III (R-3H.TBA)₃ where R = C₉H₄O₄NSI. The method is satisfactory for the determination of vanadium in steels, alum and other samples without preliminary separations.     

Extraction and spectrophotometric determination of vanadium(V) with ferron

Various metal complexes of 7-iodo-8-hydroxyquinoline-5-sulphonic acid (ferron) were found to be selectively extracted into immiscible alcohols. Vanadium(V) is almost completely extracted into n-butanol in a single extraction from solutions which are 0.05 M in sulphuric acid. A sensitive and selective spectrophotometric method can be based on this extraction. Beer's law is obeyed up to 15.3 μg of vanadium per ml; the sensitivity of the color reaction is 0.011 μg of vanadium per cm² at 430 mμ. The interference of iron(III) can be eliminated by adding excess pyrophosphate. The extracted species appears to contain vanadium, ferron and n-butanol in the ratio 1:2:4.     

Anion-exchange separation and spectrophotometric determination of vanadium in silicate rocks

A combined anion-exchange-spectrophotometric method has been developed for the determination of vanadium in silicate rocks. A rock sample weighing about 0.1 g is decomposed with a mixture of sulphuric and hydrofluoric acids and after removal of HF the residue is taken up with dilute sulphuric acid. This solution is adjusted to be 0.05M in sulphuric acid and contain 0.3% hydrogen peroxide, and is passed through a column of Amberlite CG 400 (sulphate form). The sorbed vanadium is eluted with 30 ml of 1M hydrochloric acid. The effluent is evaporated to dryness, made 0.1M in hydrochloric acid and 3% in hydrogen peroxide content, and passed through a column of Amberlite CG 400 (chloride form) to get rid of accompanying thorium and zirconium. Vanadium is stripped by elution with 20 ml of 1M hydrochloric acid and subsequently determined spectrophotometrically with 4-(2-pyridylazo)resorcinol. The detection limit is 0.4 ppm.     

Ion-exchange separation and spectrophotometric determination of vanadium in environmental samples

A selective and sensitive method for the extraction and spectrophotometric determination of vanadium(V) in microgram quantities is described. The molar absorptivity of the yellow vanadium(V)-caffeic acid-Aliquat 336 extract is 1.3 x 10(4) 1.mole(-1).cm(-1) at 370nm. The method is compared with the atomic-absorption spectrometric method and applied to the trace determination of vanadium in steel, alloys, a rock and environmental samples.     

Dye-assisted chromatographic determination of aliphatic ketones and esters with brilliant green

Determinations of neutral nonchromophoric organic compounds by dye-assisted chromatography are extended to the determination of aliphatic ketones and esters by using reversed-phase conditions and a mobile phase containing Brilliant Green. Detection limits of 6–20 μg were obtained when a mobile phase containing 50% (v/v) methanol/water and 0.00010 M Brilliant Green was used with detection at 575 nm, and 0.5–2 μg with detection in the ultraviolet region. In the absence of dye the detection limits for several solutes were about four times higher than the corresponding values obtained with the dye. The dye was shown to form a dimer having a molar absorptivity two orders of magnitude smaller than that of the monomeric dye. Detection of non-chromophoric compounds is concluded to be due to the desorption of adsorbed dye by the analytes and the shift of the aggregation and hydration equilibria of the dye promoted by the organic solutes. The lowering of the capacity factors is interpreted in terms of the adsorption of dye by the column which reduces the hydrophobicity of the stationary phase.     

Gravimetric determination of beryllium with sodium oxinate

Sodium oxinate is found to precipitate Be(II) quantitatively in the pH range 7.5-8.2. The complex has the composition Be(2)O(C(9)H(6)NO)(2).2H(2)O, is stable and can be weighed directly after drying at 105-110 degrees . A method for the estimation of Be(II) and its separation from interfering elements is described. The monohydrate has been prepared from the dihydrate and characterized. The results show the presence of hydroxyl bridges in the monohydrate. Methods using various organic reagents for the direct estimation of beryllium in ores and alloys have been examined and it is found that 4-chloro-2,5-dimethoxyacetoacetanilide gives the best results. A method for the determination of be(II) in beryl without prior separation of Fe(III) and Al(III) is described.     

Rapid extraction and spectrophotometric determination of vanadium(IV) with thiothenoyltrifluoroacetone

Thiothenoyltrifluoroacetone in carbon tetrachloride-butanol (1:1) is used for extraction and spectrophotometric determination of vanadium (IV) at pH 4.5-5. The greenish-yellow complex is measured spectrophotometrically at 450 nm. The system conforms to Beer's law over the range 2-11 mug/ml of extract. The colour of the complex is stable for at least 80 hr. Vanadium (IV) was quantitatively extracted and determined in the presence of 120:1 w/w ratios of various ions. The method was made selective by using common sequestering agents or prior extraction with tributyl phosphate, diethylammonium diethyldithiocarbamate, alpha-furildioxime or acetylacetone. The method is rapid, simple, selective and sensitive.     

Extraction and spectrophotometric determination of vanadium(V) with 8-hydroxyquinoline

The extraction and spectrophotometric determination of vanadium (V) with oxine is investigated at higher acidities than described previously. Under these conditions, n-butanol and other alcohols are found to exert a synergic effect on the extraction of vanadium into benzene. In the presence of alcohol only a 6-fold ligand excess is needed for quantitative extraction in a single operation, the acidity of the aqueous medium being 0.05M with respect to sulphuric or phosphoric acid. The interference of iron(III) in the spectrophotometric determination of vanadium is suppressed by the addition of pyrophosphate. Beer's law is obeyed up to 14.0 mug of vanadium/ml and the sensitivity is 0.008 mug of vanadium/cm(2) at 390 mmu. The composition of the extracted species is found to be vanadium:oxine:n-butanol = 1:2:2.     

CGC-MS determination of mixtures of long chain aliphatic esters

A method is described for the determination of the acid and alcohol moieties in long chain wax esters. The co-eluting esters are differentiated by means of CGC-MS operating in the ion monitoring mode. The technique allows to detect ester components present in very low amounts in plant surface waxes.     

Kinetic spectrophotometric determination of trace amounts of selenium and vanadium

A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/?10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum. Received: 20 October 1998 / Revised: 17 April 1999 / Accepted: 3 June 1999     

Kinetic spectrophotometric determination of trace amounts of selenium and vanadium

A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/¶10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum.