Cyclic Voltammetry of a Fluoride-Selective Electrode in Contact with Metals

Electrochemical behavior of the interface between a LaF₃ : Eu²⁺ single-crystal fluoride-selective membrane and Bi, Sn, Pb, Sb, and Cd metallic microelectrodes is considered with the aim to apply a fluoride-selective electrode in solid-state voltammetry. The ionization-discharge processes on the metals in air, involving mobile fluoride ions from the LaF₃ membrane, were studied by cyclic voltammetry.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 265–272.Original Russian Text Copyright © 2005 by Turaeva, Pegova, Vasilevskii.     

Electrode Response of a Fluoride-Selective Electrode in Buffer Solutions of Potential-Determining Ions

The electrode response of a fluoride-selective electrode was studied in HNO₃ and Al(NO₃)₃ solutions of different concentrations and ionic strengths. We have substantiated the ion-exchange mechanism of the formation of fluoride ions in the near-membrane layer of blank buffer solutions and found that their concentration (⁰) was (4.0 ± 0.4) × 10^–6 M.     

Electrode Response and Detection Limits of a Fluoride-Selective Electrode in Anionic Buffer Solutions

It was found that electrode response and the chemical nature of the background activity appearance of a fluoride-selective electrode are identical in nonbuffered solutions and anionic complexing media. The background activity was assessed in dipotassium hydrogen citrate solutions of different concentrations. At zero ionic strength, the background activity was constant and equal to _{I = 0} = (4.0 ± 0.4) × 10^–6 M at 25.0 ± 0.1°C. Detection limits were calculated for different confidence levels. It was shown that a variation in the nature and concentration of masking ligands cannot cause a change in performance characteristics of the electrode and of the method.     

Design of a Fluoride-Selective Electrode with Internal Contact Based on a Cu(II) Ion-Selective Electrode

The design of an electrode body that provides internal contact with a LaF₃ membrane based on a Cu(II) ion-selective electrode is described. The assembled fluoride electrode was examined in terms of potential-concentration curves and potential-time response. The behavior of the fluoride ion-selective electrode with the investigated internal contact was in good agreement with the commercial fluoride electrode.     

Potentionetric Titrations Of Oxalate With A Fluoride-Selective Electrode

Abstract

Two methods for oxalate determination with a fluorideselective electrode are proposed. For oxalate amounts higher than 0.2 mmol, the joint precipitation of oxalate and standard fluoride with lanthanum(III) can be used. For smaller oxalate amounts, the precipitation of oxalate with excess of lanthanum(III) followed by back-titration with fluoride, is suitable. The end-points are located using the second derivative procedure and by means of the Gran method, respectively.     

Characteristics of Fluoride-Selective Electrode with Uranyl Salophen Receptors in Aqueous Solutions

A fluoride-selective electrode with uranyl salophen receptors is developed. Its basic electrode characteristics are the concentration range 10^-4-10^-1 M and the slope of the electrode function 56 mV/pF^-. The electrode shows a high fluoride selectivity in the presence of such interfering anions as sulfate, chloride, and nitrate.     

Anodic Stripping Voltammetry Using a Vibrating Electrode

This work proposes a vibrating microwire electrode as working electrode in stripping voltammetry. The vibration was found to maintain a constant and thin (1–2 μm) diffusion layer during the deposition step. The electrode vibration eliminated the need for external stirring of the solution, thus facilitating in situ detection in the environment. The vibration was effected by fixing a low‐voltage (3 V), asymmetric, electrical rotor to the working electrode (a gold microwire of either 5 or 25 μm). The sensitivity of the vibrated electrode was ca. 22×greater than stationary. Measurements of copper (4 nM) by anodic stripping voltammetry using the vibrating electrode had a low standard deviation (1% for n=6) indicating that the diffusion layer had only minor variability. The agitation mechanism was unaffected by water moving at >2 m s^?1 and by water pressure equivalent to a depth of >40 m, indicating its suitability for in situ measurements. The vibrating probe was used for in situ detection of copper by anodic stripping voltammetry to a depth of 6 m. Using a 5 min deposition time, the limit of detection for labile copper was 38 pM.     

Graphite Composite Electrode in Voltammetry

Abstract

Graphite composite electrode (CCE30), composed from 30% of graphite powder and 70% of epoxy resin, was tested. Determination of aminocompounds, oxidation of adenine and guanine, and determination of manganese by differential pulse voltammetry (DPV) and direct current voltammetry (DCV) was tested in positive potential area.     

管式电极流体动力催化伏安法的研究

Blaedel等曾证明管式电极在层流条件下的扩散电流方程,随后在管式电极上对极谱催化电流进行了研究,但该理论只适用于化学反应非常快及非常慢的情况。Koichi等运用与Blaedel不同的处理方法,导出了通道电极上更为精确的催化电流方程。     

Anodic Stripping Voltammetry with Galinstan as Working Electrode

The liquid alloy galinstan is used to determine low concentrations in microgram per liter level of trace metals like copper, cadmium, lead, bismuth, antimony and thallium using anodic stripping voltammetry. Like the conventionally applied HMDE, the hanging galinstan drop electrode (HGDE) is able to accumulate the investigated metal ions at the electrode surface. Hence, simultaneous determination of Pb and Cd is possible. Both, DPASV and SWASV were used as measuring methods. The influence of different parameters like accumulation potential and time and the frequency in SWASV were studied. By the use of acetic buffer solutions, the potential window reaches from ?900 mV to 150 mV. The limit of detection (LOD) varies from 6 ppm (worst case, Sb³⁺) to 2 ppb (best case, Pb²⁺). Therefore, the use of galinstan in the form of the HGDE is possible as a “mercury‐free” and environmentally friendly electrode in stripping analysis.     

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.     

双嘧达莫在玻碳电极上的阳极伏安法研究

用直流伏安法(DCV),微分脉冲伏安法(DPV)和循环伏安法(CV)在玻碳电极(GCE)上研究了双嘧达莫(DPM)在不同介质中的阳极伏安行为,发现在0.01mol/LCHl溶液中于0.62V(vs.Ag/AgCl)右左生产一个阳极氧化峰,其峰高与浓度的线性方程分别为r=0.0004 0.17C(0.05~1.0mg/L)和y=0.052 0.22C(0.5~10mg/L). 在此体中大多数金属离子和20多种有机生代物质不干扰测定,采用该方法可不经分离,直接测定药物制剂和尿样吕DPM的含量,同时对DPM的电极反反应机理进行了探讨.     

悬液电极萃取碘伏安法的研究

分别以硝基苯(NB)、苯乙酮(ACP)、4-甲基-2-戊酮(MIBK)三种不同的有机溶剂作为悬液电极, 利用三电极体系伏安法比较其在液/液界面上对碘的不同的电化学特性. 在上述研究的基础上, 选用MIBK作为有机溶剂对碘进行萃取分析, 利用伏安法测定了水溶液中Cu(II)的含量, 同时研究了温度和萃取时间对该体系的影响.     

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.     

On-Site Determination of Methylmercury by Coupling Solid-Phase Extraction and Voltammetry

A measurement and speciation procedure for the determination of total mercury (Hg_TOT), inorganic mercury (Hg_IN), and methylmercury (CH₃Hg) was developed and the applicability for on-site determination was demonstrated. A simple, portable sample pretreatment procedure was optimized to extract the analytes. Home-made columns, packed with a new sorbent material called CYXAD (CYPHOS 101 modified Amberlite XAD), were used to separate the two forms of the analyte. Hg_TOT and CH₃Hg were determined by anodic stripping voltammetry (ASV), using a solid gold electrode (SGE). Two certified reference materials (BCR-463 Tuna Fish and Tuna Fish ERM-CE 464) and eight fresh fishes were analyzed. Then, the results that were obtained following the optimized portable procedure were compared with the concentrations obtained, using a direct mercury analyzer (DMA). This quantification, using the two techniques, demonstrated the good performance of the proposed method.     

对位叠式循环方波伏安法：Ⅱ.平行催化体系

本文提出平行催化体系的对位叠式循环方波伏安法，并对共作了系统的研究，推导了这一方法的催化电流理论方程，并用验验证这理论的正确性，得到其各脉冲电流皆为同方向，对位叠式循环催化电流相当于将电流叠加４次，而波形不受方波幅度大小的影响，因而灵敏度和分辨率有较大提高，优于其它方波伏安法。     

奥美拉唑在碳糊电极上的吸附伏安测定法研究

研究了奥美拉唑在碳糊电极上的电化学行为及检测方法 ;在1.2mol·L -1H2SO4 底液中 ,通过富集用碳糊电极吸附伏安法测定奥美拉唑 ;阴极峰电位为0.403V(vsSCE) ,峰电流与奥美拉唑的浓度在7.8×10-8～3.7×10-5 mol·L-1 范围内呈良好的线性关系 ;该法的检出限为1.43×10-8 mol·L-1;用标准加入法测得回收率范围为94 %～102 % ;对奥美拉唑胶囊用该法进行了测定 ,获得了满意的结果 ;该法的优点是成本低 ,操作方便 ,重复性好及检出限较低 ;对电极响应机理进行了探讨 ,奥美拉唑的电极过程是一个两电子两质子的准可逆过程     

Determination of Caffeine Using a Simple Graphite Pencil Electrode with Square-Wave Anodic Stripping Voltammetry

A simple commercial graphite pencil electrode (GPE) was utilized for monitoring caffeine using the square-wave anodic stripping voltammetry (SWASV) method. This method was applied to determine the caffeine levels in several tea samples, which yielded a relative error of 1% in the concentrations. Caffeine was deposited at 0.0V (vs. Ag/AgCl), then reduced at +1.40V to strip it on the GPE. Optimal experimental conditions for the analysis were found to be as follows: pH value of 9 for the medium; deposition potential of 0.0V; deposition time of 120s; SW frequency of 25Hz; SW amplitude of 45mV, and step potential of 6mV. Given these optimum conditions, a linear range was observed within the concentration of 0500mgL^–1. At caffeine concentrations of 50.0, 250.0, and 500.0mgL^–1, the relative standard deviations in measured concentrations (n=12) were 0.19, 0.09, and 0.11%, respectively. The detection limit was found to be 9.2mgL^–1, which is comparable with the result obtained using a carbon paste electrode, equivalent to 8.2mgL^–1.     

叠式循环阶梯脉冲伏安法：Ⅰ.简单可逆电极体系

本文提出循环阶梯脉冲伏安法和对位叠式循环阶梯脉冲伏安法，推导出简单可逆电极体系的电流方程，研究了峰电流与诸因素的关系，并进行了实验验证，发现对位叠式循环阶梯脉冲伏安法有较多的优点     

对位叠式循环方波伏安法：Ⅰ.简单可逆电极体系

本文提出叠式循环方波伏安法和对位叠式循环方波伏安法，对简单可逆电极体系的理论作了推导和验证，经对各种电流的比较，发位叠式循环方波伏安法有较多的优点。较之其它方波伏安法灵敏。