Silver Amalgam Film Electrode of Prolonged Application in Stripping Chronopotentiometry

The utility of the cylindrical silver‐based mercury film electrode of prolonged analytical application in stripping chronopotentiometry (SCP) was examined. This electrode allowed us to obtain good reproducibility of results owing to the special electrode design, which enables regeneration of the thin layer before each measurement cycle. The accessible potential window in KNO₃ (pH 2), acetate and ammonia buffers was defined, and the optimal conditions (i.e., stripping current, deposition potential and deposition time) for the determination of Cd and Pb traces were selected. The detection limits, obtained for an accumulation time of 60 s, were 0.023 μg/L for Cd and 0.075 μg/L for Pb. The response increases linearly with Cd, Pb and Zn concentration, up to at least 100 μg/L. It was also shown that the proposed procedure ensures excellent separation of the In and Tl, Pb and Tl or the In and Cd signals. The method was tested with dolomite and lake sediment samples, and good agreement with reference values was achieved. The obtained results showed good reproducibility (RSD=5–6%) and reliability.     

Performance of a Bismuth Bulk Rotating Disk Electrode for Heavy Metal Analysis: Determination of Lead in Environmental Samples

The bismuth bulk electrode is proposed here for the first time in the rotating configuration (BiB‐RDE) as the electrode of choice for voltammetric analysis of selected heavy metal ions. Optimization of chemical and instrumental parameters was carried out to develop a reliable and convenient method for the determination of Zn(II), Cd(II) and Pb(II) by SWASV. Appropriate detection limits were found for environmental monitoring applications in the medium – low µg/L range. The method was validated for Pb(II) determination by certified reference materials. Successful application to the determination of Pb(II) in samples of fortified rainwater and sewage sludge from a steel industry is described.     

Catalytic Adsorptive Stripping Voltammetry of Cobalt in the Presence of Nitrite at an In Situ Plated Bismuth Film Electrode

For the first time an in situ plated bismuth film electrode has been applied to catalytic adsorptive stripping voltammetry of cobalt in the presence of nitrite. At optimised conditions bismuth film was plated before each measurement for 30 s at ?1.0 V from a sample solution with the added supporting electrolyte and Bi(III) in the form of its complex with tartrate. The calibration graph for Co(II) for an accumulation time of 120 s was linear from 5×10^?10 to 1×10^?8 mol L^?1. The detection limit was 1.1×10^?10 mol L^?1. The proposed procedure was applied for Co(II) determination in certified water reference material.     

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.     

Nafion汞膜修饰电极用于阳极溶出伏安法测定痕量铋的研究

本文报道了Nafion汞膜修饰电极及其用于阳极溶出伏安法测定未处理尿样,水样及土样中痕量铋的研究。样品中常共存的Pb(Ⅱ)、Sb(Ⅲ )等19种阳离子及尿样中共存的有机物在实验条件下不干扰。本法不仅选择性好,而且灵敏度也较高。线性范围为2×10~(-10)～1×10~(-7)mol/L。回收率为94～105％。     

铋膜电极溶出伏安法测定食品中痕量重金属

以铋膜电极为工作电极,采用微分脉冲阳极溶出伏安法直接测定食品样品中痕量铅、镉和锌。在富集电位-1.4V,富集时间180s,铋膜质量浓度150μg·L-1的条件下,铋膜电极对铅、镉和锌的氧化溶出具有良好的电化学响应。铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的质量浓度在5.0~40μg·L-1的范围内与其阳极溶出峰电流呈线性关系,铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的检出限(3S/N)分别为0.80,0.65,0.58μg·L-1。对25μg·L-1铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)溶液用铋膜电极连续测定15次,相对标准偏差分别为6.2%,5.1%,7.1%。方法应用于食品中痕量重金属的测定,测定结果与石墨炉原子吸收光谱法的测定值相符。     

Adsorptive Stripping Voltammetric Measurements of Trace Molybdenum at the Bismuth Film Electrode

Bismuth‐film electrodes on glassy‐carbon substrates have been successfully applied for adsorptive‐stripping voltammetric measurements of trace molybdenum in the presence of chloranilic acid (CAA). The procedure is based on the preconcentration of the molybdenum‐chloranilic acid complex at a preplated bismuth film electrode held at ?0.55 V (vs. Ag/AgCl), followed by a negatively‐sweeping square‐wave voltammetric scan. Factors influencing the adsorptive stripping performance, including different ligands, solution pH, CAA concentration, preconcentration time and potential, have been optimized. The response compares favorably with that observed at mercury film electrodes, and is linear over the 5–50 μg/L Mo concentration range (one min preconcentration). A detection limit of 0.2 μg/L molybdenum is obtained following a 10 min accumulation. High stability is indicated from the reproducible response of a 100 μg/L molybdenum solution (n= 60; RSD=2.6%). Applicability to seawater samples is demonstrated.     

化学修饰铋膜电极的制备和应用研究进展

本文综述了近年来化学修饰铋膜电极的制备和应用的研究进展。首先介绍了铋膜电极的制备方法,然后介绍铋膜电极的应用和研究进展,包括铋膜电极在检测重金属离子、硝基酚类化合物、药物、杀虫剂及一些生物活性物质等方面的应用。     

The Influence of the Electrodeposition Conditions on the Electroanalytical Performance of the Bismuth Film Electrode for Lead Determination

The bismuth film is a great promise as a suitable material to replace the mercury electrodes due to its low toxicity and good cathodic potential range. This work studies the influence of the electrodeposition conditions in the morphology and electroanalytical performance of the bismuth film electrodeposited onto copper electrode. The bismuth films were obtained in nitric or hydrochloric acid solutions with and without the presence of sodium citrate. The films were characterized by field emission scanning electron microscopy (FE‐SEM) and scanning electron microscopy with energy dispersive X‐ray spectrometry (SEM‐EDX). The microscopic analysis of the bismuth film obtained in HCl solution with sodium citrate (BIFE‐Cit) showed more homogeneous structure with higher content of bismuth than the film obtained in HCl only (BiFE‐HCl). The BiFE‐Cit exhibited a better analytical performance for lead with good adherence to the copper substrate.     

A Study on Operational Parameters for Advanced Use of Bismuth Film Electrode in Anodic Stripping Voltammetry

A study is presented on the characterization, evaluation and optimization of several key operational parameters for a reliable and effective use of a bismuth film electrode (BiFE) as an advanced replacement of the mercury film electrode in anodic stripping voltammetric measurements of trace heavy metals. Applying in situ preparation of the BiFE and employing lead(II) and cadmium(II) as model analyte ions, key parameters including bismuth precursor salt and substrate surface (platinum, gold, glassy carbon, carbon paste, carbon fiber) for bismuth plating, concentration as well as cationic and anionic composition of the measurement solution, solution pH and temperature, potential interferents, and stripping modes were carefully examined for their effects in the preconcentration and stripping steps. Parameters such as substrate surface (except platinum), precursor salt, solution matrix and temperature showed no or little impact on the BiFE performance in stripping analysis. On the other hand, the BiFE performance was found to be dependent on the solution pH (with maximum efficiency in the range of 4 to 5), on the stripping mode (with square‐wave voltammetry as the best choice) and to a certain degree on the presence of surface active substances. The results revealed that the non‐toxic solid‐state BiFE is applicable under a wide variety of conditions which proves it highly suitable for practical work in environmental trace heavy metal analysis.     

Stripping Chronopotentiometry and Stripping Voltammetry of Mixtures of Heavy Metal Ions Producing Close Signals: The Cd(II)‐Pb(II)‐Phthalate System

The effects of the proximity of the signals of two heavy metal ions in stripping voltammetry (SV) and constant‐current stripping chronopotentiometry (SCP) is studied at mercury drop (HMDE) and mercury film (MFE) electrodes. For this purpose, the Cd(II)‐Pb(II)‐phthalate system is used, taking advantage of the approaching of the signals corresponding to Cd(II)‐phthalate and Pb(II)‐phthalate labile complexes as phthalate is added to mixtures of Cd(II) and Pb(II)‐ions. The results are compared with those obtained by differential pulse polarography (DPP) and by stripping measurements on the Pb(II)‐phthalate system alone, showing discrepancies in SCP data under nondepletive conditions and negligible differences in the other cases.     

A Simulation of an Anion‐Induced Adsorption of Metal Ions in Pseudopolarography Using a Thin Mercury Film Covered Rotating Disk Electrode

A theory of the influence of anion‐induced adsorption of metal ions in pseudopolarography using the thin mercury film covered rotating disk electrode is developed. The model is developed assuming that the metal ion is forming several labile complexes with the ligand which is present in a great excess, and that only one complex species is adsorbed following a linear isotherm. The results obtained assuming steady‐state conditions are compared with the simulation of transient processes using Galerkin and finite difference methods. It is shown that the adsorption of metal complexes on the disk electrode surface does not prevent the determination of the stability constants.     

预镀铋膜修饰铂电极差分脉冲溶出伏安法测定痕量铅、镉

采用预镀铋膜法修饰铂电极,用该电极对痕量Pd、Cd同时进行了差分脉冲溶出伏安法测定,Pd、Cd在富集中和铋形成类似于汞齐的合金,溶出峰良好。讨论了在不同沉积液和沉积时间下得到的铋膜电极的性能和富集时间、富集电位及底液pH对金属离子测定的影响。在优化的实验条件下,分别对10~100μg/L、20~200μg/L和50~500μg/L3个不同浓度系列的Pb2 、Cd2 进行了同时测定,Pb、Cd溶出峰电流与Pb2 、Cd2 浓度呈良好的线性关系(r≥0.999),Pb2 、Cd2 浓度的线性范围均为10~500μg/L;富集时间为180 s时,Pb2 、Cd2 的检出限分别为0.38μg/L和0.82μg/L。利用本方法测定了蔬菜中Pb的含量,并与原子荧光分析法做了对比,结果令人满意。     

神经递质多巴胺在AQ修饰组合微电极上的伏安行为及其伏安溶出法测定

本研究了神经递质多巴胺（ＤＡ）在ＡＱ聚合物薄膜修饰组合微盘电极上的电化学行为。结果表明，在ｐＨ７．０的磷酸缓冲溶液中，修饰组合微盘电极经电化学处理后，ＤＡ的氧化还原峰电位差较小（约为８０ｍＶ），氧化峰、还原峰的峰形比较对称。在选定条件下，ＤＡ的伏安溶出峰电流与浓度在１．０×１０＾－６～８．０×１０＾－４ｍｏｌ／Ｌ范围内呈线性关系。厚的ＡＱ膜修饰组合微电极可基本上消除抗坏血酸的干扰。利用ＡＱ膜修饰     

Enhanced Resolution of Copper and Bismuth by Addition of Gallium in Anodic Stripping Voltammetry with the Bismuth Film Electrode

This paper presents the enhanced analysis of copper on a bismuth electrode upon addition of gallium(III). The presence of gallium alleviates the problems of overlapping stripping signals usually observed between copper and bismuth when using the Bismuth Film Electrode. In addition, it has been found that the presence of gallium improves the reproducibility of the bismuth stripping signal. Simultaneous deposition of copper and bismuth at ?1500 mV for 2 minutes in a supporting electrolyte composed of 0.1 M pH 4.75 acetate buffer with 250 μg L^?1 gallium yields well resolved copper and bismuth signals when analyzed with square‐wave anodic stripping voltammetry. Simultaneous analysis of copper and lead yielded linear calibration plots in the range 10 to 100 μg L^?1 with regression coefficients of 0.997 and 0.994 respectively. The theoretical detection limit for copper was calculated to be 4.98 μg L^?1 utilizing a 2 minutes deposition time. The relative standard deviation for a copper concentration of 50 μg L^?1 was 1.6% (n=10).     

铋膜电极方波吸附溶出伏安法测定纺织品中痕量钴和镍

本文建立了在铋膜修饰电极上采用方波吸附溶出伏安法同时测定纺织品中痕量Co2+和Ni2+的方法.以NH3-NH4Cl作为缓冲液,在丁二酮肟浓度为10 μmol/L的体系中,Co2和Ni2+的还原峰电位分别为-1.13 V和-1.03 V.当缓冲溶液pH为9.2,富集电位为-0.7V,富集时间为200 s时,C02 +和Ni2+在0.5～50 μg/L范围呈现良好的线性关系,相关系数R2＞0.99,其检出限分别为0.79 μg/L和0.96 μg/L,其它金属离子的干扰较小.采用标准加入法测定纺织品中Co>和Ni2+,回收率在94.88％～104.14％之间.     

A Novel Cell Design for the Improved Stripping Voltammetric Detection of Zn(II), Cd(II), and Pb(II) on Commercial Screen‐Printed Strips by Bismuth Codeposition in Stirred Solutions

A novel electrochemical cell design is proposed to allow fast, reproducible and highly efficient convective transport of dissolved substances to screen‐printed electrochemical three‐electrode strips mounted on miniaturized plastic vessels, with the goal of improving detection limits in disposable electrochemical stripping field sensors. The experimental configuration has been tested for accumulation of the selected heavy metals ions Zn(II), Cd(II), and Pb(II), codeposited with bismuth ions on a carbon disk screen‐printed working electrode before detection by square wave anodic stripping voltammetry. Chemical and instrumental variables of the proposed device and associate electrochemical method were optimized. Selected parameters gave detection limits in the low ng mL^?1 range with moderate deposition time (120 s). Practical applicability was tested on certified water and real samples (tap water and waste water), with acceptable results, suggesting potential usefulness for field environmental monitoring of heavy metals.     

An Electrochemical Study of the Interactions Between Trace Metals and Humic Substances in Freshwaters by Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode

An improved theoretical approach to Anodic Stripping Voltammetry with a Thin Mercury Film Rotating Disk Electrode for elucidating the nature of the interactions of Pb(II), Cd(II) and Zn(II) with humic substances in model solutions of Laurentian fulvic acid, and of Pb(II), Cd(II), Zn(II) and Cu(II) in freshwaters, is presented. Conditional stability constants of Pb(II), Cd(II) and Zn(II) complexes decreased with the ionic potential (z²/r) and increased with softness of the metal ion, indicating strong affinity of soft, polarizable donor ligands on humic substances for softer metal ions, resulting in an appreciable covalent character in electrostatic bonding between the metals and humic substances.     

Investigation of Copper(II) Interference on the Anodic Stripping Voltammetry of Lead(II) and Cadmium(II) at Bismuth Film Electrode

The bismuth‐coated electrode is known to be prone to errors caused by copper(II). This study investigates copper(II) interference at bismuth film electrode for the detection of lead(II) and cadmium(II). It was conducted using glassy carbon electrode, while the bismuth film was plated in situ simultaneously with the target metal ions at ? 1200 mV. Copper(II) presented in solution significantly reduced the sensitivity of the electrode, for example there was an approximately 70 % and 90 % decrease in peak signals for lead(II) and cadmium(II), respectively, at a 10‐fold molar excess of copper(II). The decrease in sensitivity was ascribed to the competition between copper and bismuth or the metal ions for surface active sites. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) analysis suggested a large decrease in the amount of bismuth nanoparticles formed on the electrode surface in the presence of copper(II) occurred, validating the competition between copper and bismuth ions for surface active sites. Recovery of the stripping signal of lead(II) and cadmium(II) was obtained by adding ferrocyanide ion to the solution. Finally, the proposed method was successfully applied to determine lead(II) and cadmium(II) in water samples and the method was validated by ICP‐MS technique.     

Determination of Trace Amounts of Copper in Tap Water Samples with a Calix[4]arene Modified Carbon Paste Electrode by Differential Pulse Anodic Stripping Voltammetry

A calix[4]arene modified carbon paste electrode was used for trace determination of copper. The study of the preconcentration of copper as well as the other heavy metal ions at the modified electrode, with subsequent measurement by differential pulse anodic stripping voltammetry (DPASV), indicates the efficient open‐circuit accumulation of the analytes onto the electrode. Many parameters such as the composition of the paste, pH, preconcentration time and stirring rate influence the response of the measurement. The procedure was optimized for copper determination. For a 10‐minute preconcentration time at pH 6.5–7.5, the detection limit (LOD) was 1.1 μg L^?1. The optimized method was successfully applied to the determination of copper in tap water sample by means of standard addition procedure. The copper content of the sample was comparable with the result obtained with AAS method.