Determination of Selenium (IV) in Biological Sample by Cathodic Stripping Voltammetry

Abstract

The determination of selenium (IV) in biological sample using cathodic stripping voltammetry is reported. It was found possible to determine selenium directly in biological samples containing such metals as zinc (II), lead (II), iron (III), arsenic (III) and magnesium (II). The results for selenium in bovine liver are reported.     

Determination of Selenium in Foodstuffs by Cathodic Stripping Voltammetry at a Mercury–Graphite Electrode

A universal procedure was developed for the voltammetric determination of total selenium in various foodstuffs. The procedure involves the mineralization of a test sample with magnesium nitrate followed by the reduction of selenium(VI) to selenium(IV) in 6 M HCl and the determination of selenium by cathodic square-wave voltammetry at a mercury–graphite electrode in an HCl solution in the presence of copper and mercury ions.     

Determination of Enalapril by Stripping Voltammetry at a Mercury Film Electrode

A procedure was developed for determining 4.0 × 10^–6 to 2.6 × 10^–3 M enalapril in model solutions and blood serum by anodic stripping voltammetry at a mercury film electrode.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 5, 2005, pp. 495–498.Original Russian Text Copyright © 2005 by Gusakova, Ivanovskaya.     

Determination of Arsenate Ions by Stripping Voltammetry at a Silver Electrode

Trace amounts of arsenate ions can be determined by stripping voltammetry at a silver electrode. Cathodic polarization curves exhibited one current peak corresponding to the electrostripping of a compound formed by arsenate ions with silver. The areas of stripping peaks expressed in Coulomb can serve as analytical signals in the determination of arsenate ions by stripping voltammetry.     

Determination of Phosphate by Cathodic Stripping Voltammetry at a Glassy Carbon Electrode

Abstract

The oxidation of Fe(II) in the presence of phosphate results in a film of a sparingly soluble Fe(III) phosphate salt on a glassy carbon electrode. The reaction is used as the preconcentration step in a cathodic stripping method for phosphate. The recommended procedure yields working curves which are linear over single orders-of-magnitude down to 0.1 ppm, With a 40-minute preconcentration time, 40 ppb phosphate can be detected. The method is free of interference by chloride and sulfate.     

Determination of Sulpiride by Linear Sweep Stripping Voltammetry at a Mercury Electrode

This paper reports the electrochemical properties of sulpiride at a mercury electrode,especially its adsorptive characteristic,Sulpiride dissolved in a supporting electrolyte of a McIlvaine buffer at pH 6.8 represents a sensitive and well defined reduction wave by linear sweep stripping voltammetry.This method is based on the pre-concentration and the reduction of sulpiride at a hung mercury drop electrode.The reduction peak potential is -1.72V(vs.Ag-AgCl) and the peak current is proportional to the concentration of sulpiride in the range of 0.1-0.6 μg/mL.The detection limit is 0.0250μg/mL obtained under the experimental conditions selected in this work.The electrochemical properties of this system were investigated.and the proposed method was applied to the determination of sulpiride in pharmaceutical tablets with satisfactory results,It was compared well with the UV spectrophotometric method,showing a superior sensitivity.     

Determination of Trace Vanadium by Adsorptive Stripping Voltammetry at a Carbon Paste Electrode

A method for the voltammetric determination of vanadium using a carbon paste electrode (CPE) was described. The new procedure is based on the adsorptive accumulation of the V(V)‐alizarin red S(ARS) complex onto the surface of the CPE, followed by the electrochemical reduction of adsorbed species. The optimal experimental conditions include the use of 0.10 mol/L acetate buffer (pH 5.1), 1.0×10^?5 mol/L ARS, an accumulation potential of ?0.10 V (versus SCE), an accumulation time of 2 min, a scan rate of 200 mV/s and a second‐order derivative linear scan mode. The reduction peak for the complex appears at ?0.52 V. The peak current is proportional to the concentration of V(V) over the range of 0.10–15.0 μg/L, and the detection limit is 0.04 μg/L for a 2 min adsorption time. The relative standard deviations(n=8) for 2.0 and 0.50 μg/L V(V) are 3.1 and 4.7%, respectively. The proposed method was applied to the determination of vanadium in water samples.     

Determination of Folic Acid by Adsorptive Stripping Voltammetry at a Lead Film Electrode

An adsorptive stripping voltammetric procedure for the determination of folic acid at an in situ plated lead film electrode was described. Formation of lead film on a glassy carbon substrate and accumulation of folic acid was performed simultaneously from an acetate buffer solution of pH 5.6 at the potential ?0.88 V. The measurements were carried out from aerated solutions. The calibration graph for an accumulation time of 300 s was linear from 2×10^?9 to 5×10^?8 mol L^?1. The detection limit was 7×10^?10 mol L^?1, the relative standard deviation for 2×10^?8 mol L^?1 of folic acid was 3.9%. The proposed procedure was applied to folic acid determinations in pharmaceutical preparations.     

Determination of Trace Tin by Anodic Stripping Voltammetry at a Carbon Paste Electrode

A sensitive and selective procedure for the determination of trace tin at a carbon paste electrode was described. Each measurement cycle consisted of three steps: accumulation, reduction and stripping. The tin complex with bromopyrogallol red (BPR) was accumulated on the electrode surface in 0.10 mol/L acetate buffer (pH 4.5). After electrochemical reduction of Sn(II) had been carried out, the reoxidation wave of Sn(0) appeared at ?0.69 V (vs. SCE) on scanning the potential in the positive direction in 4.0 mol/L HCl. For a preconcentration time of 2 min, the detection limit was 0.06 μg/L (5×10^?10 mol/L ) and the linear range was from 0.1 to 50 μg/L. The proposed method was applied to the determination of tin in canned food and waste water samples with satisfactory results.     

Determination of Folic Acid at a Bismuth Film Electrode by Adsorptive Stripping Voltammetry

This article reports a new simple and sensitive method for the determination of folic acid by adsorptive stripping voltammetry. The method is based on the accumulation of folic acid at a bismuth film plated in situ on a glassy carbon substrate. In order to stabilize bismuth ions, sodium potassium tartrate was added to the supporting electrolyte. The bismuth film formation and folic acid accumulation conditions were optimized and measurements were carried without solution deaeration. The calibration graph was linear from 5 × 10^?10 to 2 × 10^?8 mole per liter with an accumulation time of 180 seconds with a limit of detection of 2 × 10^?10 mole per liter. The relative standard deviation for 5 × 10^?9 mole per liter of folic acid was 3.1 percent (n = 5). The method was successfully applied for determination of folic acid in pharmaceutical preparations.     

Determination of Trace Sulfate Ions by Stripping Voltammetry at a Renewed Silver Electrode

The determination of trace sulfate ions by the known methods is considered. The most sensitive methods are based on the reduction of sulfate ions to hydrogen sulfide followed by the detection of H₂S in absorbing alkaline solutions. The properties of reducing mixtures of different compositions were tested experimentally. Working conditions were selected for the reduction of sulfate ions and the determination of sulfide ions by stripping voltammetry at a silver electrode renewed on line by cutting off a thin layer. The detection limit for sulfate ions was 10^–5% in a 0.1-g sample.     

Determination of Thiophosphamide in Aqueous Solutions by Cathodic Stripping Voltammetry at a Silver Electrode

It was demonstrated that thiophosphamide can be determined in aqueous solutions by cathodic stripping voltammetry at a silver electrode. The determination conditions were found. The detection limit for thiophosphamide in the Britton buffer solution (pH 11.2) was 5 × 10^–4M (relative standard deviation 5%), and the upper boundary of the analytical range was 3 × 10^–3M (relative standard deviation 1.5%) for a time of electroaccumulation of 5 min.     

Rapid Determination of Mercury in Water by Stripping Voltammetry at a Gold-Modified Carbon Electrode

A procedure was developed for determining mercury in natural water by stripping voltammetry on a gold-modified carbon electrode. The concentration dependence of the anodic stripping current of mercury is linear in the range 0.02–5 g/L Hg(II). The interference of Fe(III), Cu(II), Cl^–, Br^–, I^–, and F^– ions with the determination of mercury was studied. Ozonation was used for rapid sample preparation. The detection limit for mercury was 0.02 g/L at an electrolysis time of 5 min.     

Indirect Determination of Trace Copper(II) by Adsorptive Stripping Voltammetry with Zincon at a Carbon Paste Electrode

Traces of copper(II) can be determined by adsorptive stripping voltammetry using 2‐carboxy‐2′‐hydroxy‐5′‐sulfoformazyl benzene (Zincon) as complex forming reagent. First in phosphate buffer pH 6.4, copper(II)‐Zincon complex was adsorbed on carbon paste electrode (CPE) with an accumulation potential of 0.6 V. Following this, adsorbed complex was oxidized and detected by differential pulse voltammetric (DPV) scan from 0.6 to 1.0 V. The effective parameters in sensor response were examined. The detection limit (DL) of copper(II) was 1.1 μg/L and relative standard deviations (RSDs) for 10 and 200 μg/L Cu(II) were 1.81 and 1.03%, respectively. The calibration curve was linear for 2–220 μg/L copper(II). The resulting CPE does not use mercury and therefore, has a positive environmental benefit. The method, which is reasonably sensitive and selective, has been successfully applied to the determination of trace amount of copper in water and human hair samples.     

阴极溶出伏安法测定异烟肼的研究

报道了吸附阴极溶出伏安法测定异烟肼。探讨了电极反应机理。在０．０１ｍｇｏｌ／Ｌ硼砂底液中，峰电位为－１．４０Ｖ。峰电流与异烟肼浓度在４．０＊１０＾－７－１．５＊１０＾－５ｍｏｌ／Ｌ范围内呈良好的线性关系，相关系为０．９９１３。该方法用于异烟肼片剂的测定，获得满意结果。     

Determination of Potassium Xanthate in Aqueous Solutions by Cathodic Stripping Voltammetry at a Silver Electrode

It was shown that potassium xanthate can be determined in aqueous solutions by cathodic stripping voltammetry at a silver electrode. The detection limit for potassium xanthate electroaccumulated for 5 min and determined under the optimum conditions in the Britton buffer solution with pH 11.98 was 1.8 × 10^–5 M at a relative standard deviation of 5%; the upper boundary of the analytical range was 5 × 10^–4 M at a relative standard deviation of 1.5%.     

Stripping Voltammetry of Thallium at a Film Mercury Electrode

The electrochemical dissolution of thallium from the surface of a mercury film electrode was studied in different supporting electrolytes. The effects of the concentration of thallium(I), electrolysis potential and time, and the potential sweep rate on anodic voltammograms were studied. The electrode process in solutions containing EDTA, HCl, and ascorbic acid at a potential sweep rate of 0.020 V/s is reversible. A stripping voltammetric procedure was developed for determining thallium(I) in the concentration range 1 × 10^–9 to 5 × 10^–7 M. The detection limit (3, n = 3) is 5 × 10^–10 M.     

Determination of Thallium in a Flow System by Anodic Stripping Voltammetry at a Bismuth Film Electrode

A procedure for trace thallium determination by anodic stripping voltammetry at a bismuth film electrode is presented. Measurements were performed in a flow system. The calibration graph was linear from 2×10^?9 to 3×10^?8 mol L^?1 for an accumulation time of 300 s. A detection limit for Tl⁺ following deposition time of 300 s was 6×10^?10 mol L^?1. The relative standard deviation at Tl⁺ concentration 2×10^?8 mol L^?1 was 3.9%. For determination of thallium in complex matrices the procedure for elimination of interferences from foreign ions exploiting anion exchange resin was proposed. The procedure proposed was validated by analysis of rain water certified reference material.     

Determination of Gold by Stripping Voltammetry Using a Modified Carbon Paste Electrode

It was demonstrated that microgram amounts of gold can be determined by stripping voltammetry at a modified carbon paste electrode, and the conditions for such a determination were optimized. The developed procedures were applied to the analysis of model mixtures of real materials. The performance characteristics were estimated. In all cases, the relative standard deviation was no worse than 10%.     

阴极溶出伏安法测定硒酵母中微量硒

建立了用阴极溶出法测定硒酵母中硒含量的分析方法。硒酵母样品用H2 SO4 -HClO4 -Na2 Mo4 消解液消解 ,用浓HCl加热还原Se (Ⅵ )为Se (Ⅳ ) ;三电极包括汞膜电极 (工作电极 ) ,Ag -AgCl (参比电极 ) ,Pt电极 (辅助电极 ) ,优化条件为 :支持电解质为 3mol LHCl,预电解电位为 -2 0 0mV ,富集时间为 1 5 0s ,峰电位在 -0 4 4V。测定Se (Ⅳ )的标准曲线线性范围为 1 0～ 80 μg/L。测定硒酵母中的硒的结果为 8 1 0× 1 0 -3 ,与分光光度法测定结果相比 ,相对误差为7 2 %。