Determination of trace amounts of lead and cadmium using a bismuth/glassy carbon composite electrode

We examined the use of a bismuth-glassy carbon (Bi/C) composite electrode for the determination of trace amounts of lead and cadmium. Incorporated bismuth powder in the composite electrode was electrochemically dissolved in 0.1 M acetate buffer (pH 4.5) where nanosized bismuth particles were deposited on the glassy carbon at the reduction potential. The anodic stripping voltammetry on the Bi/C composite electrode exhibited well-defined, sharp and undistorted peaks with a favorable resolution for lead and cadmium. Comparing a non-oxidized Bi/C composite electrode with an in-situ plated bismuth film electrode, the Bi/C composite electrode exhibited superior performance due to its much larger surface area. The limit of detection was 0.41 μg/L for lead and 0.49 μg/L for cadmium. Based on this study, we are able to conclude that various types of composite electrodes for electroanalytical applications can be developed with a prudent combination of electrode materials.     

Electrochemical Properties and Range of Application of Mixed Gold Bismuth Electrodes

Electrochemical properties for mixed gold‐bismuth electrodes have been evaluated. Increased overpotential towards the hydrogen evolution reaction (HER) was found as a function of increased bismuth content in the gold‐bismuth mixture. Compared to a bare gold electrode, the overvoltage was increased by 80 mV for gold with 2% bismuth added (AuBi2), 170 mV for 6% bismuth added (AuBi6), and 580 mV for 25% bismuth added (AuBi25). Cyclic voltammetry (CV) in a NaOH solution was also carried out to study the formation of different oxide products on the surface. The practical use of such electrodes was demonstrated by differential pulse anodic stripping voltammetry (DPASV) for the detection of copper and mercury, and good linearity was found even for concentrations down to 0.25 μg/L. In addition to stability tests in NH₄Cl, the analytical use and stability over time were evaluated in purified scrubbing water and polluted river water.     

Disposable Bismuth Oxide Screen Printed Electrodes for the High Throughput Screening of Heavy Metals

We present a simplified approach for the trace screening of toxic heavy metals utilizing bismuth oxide screen printed electrodes. The use of bismuth oxide instead of toxic mercury films facilitates the reliable sensing of lead(II), cadmium(II) and zinc(II). A linear range over 5 to 150 μg L^?1 with detection limits of 2.5 and 5 μg L^?1 are readily observed for cadmium and lead in 0.1 M HCl, respectively. Conducting a simultaneous multi‐elemental voltammetric detection of zinc, cadmium and lead in a higher pH medium (0.1 M sodium acetate solution) exhibited a linear range between 10 and 150 μg L^?1 with detection limits of 5, 10 and 30 μg L^?1 for cadmium, lead and zinc respectively. The sensor is greatly simplified over those recently reported such as bismuth nanoparticle modified electrodes and bismuth film coated screen printed electrodes. The scope of applications of this sensor with the inherent advances in electroanalysis coupled with the negliable toxicity of bismuth is extensive allowing high throughput electroanalysis.     

A Study of Nafion‐Coated Bismuth‐Film Electrode for the Determination of Zinc,Lead, and Cadmium in Blood Samples

In this article a sensitive differential pulse stripping voltammetry technique on Nafion‐coated bismuth‐film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L^?1 for Cd(II), 0.13 μg L^?1 for Pb(II), and 0.97 μg L^?1 for Zn(II) respectively.     

Stripping Voltammetry with Bismuth Modified Graphite‐Epoxy Composite Electrodes

The attractive performance of graphite‐epoxy composite electrodes (GECE) surface‐modified with a bismuth film (Bi‐GECE) for simultaneous and separate stripping determination of trace amounts of heavy metals (lead, cadmium and zinc) is described. Several key parameters have been optimized. Bi‐GECEi electrode shows superior accumulation properties when compared to bare GECE or even to Hg‐GECE. Bi‐GECE exhibits well‐defined, undistorted, reproducible and sharp stripping signals with RSD of 2.99%, 1.56% and 2.19% for lead, cadmium and zinc respectively. Detection limits of 23.1, 2.2 and 600 μg/L for lead, cadmium and zinc were obtained. Sharp peaks with high resolution (of neighboring signals) that permit convenient multi‐elemental measurements resulted. The applicability of the electrodes to the real samples (tap water and soil sample) was also tested and promising results with good recoveries were obtained.     

Determination of trace metals by anodic stripping voltammetry using a bismuth-modified carbon nanotube electrode

A bismuth-modified carbon nanotube electrode (Bi-CNT electrode) was employed for the determination of trace lead, cadmium and zinc. Bismuth film was prepared by in situ plating of bismuth onto the screen-printed CNT electrode. Operational parameters such as preconcentration potential, bismuth concentration, preconcentration time and rotation speed during preconcentration were optimized for the purpose of determining trace metals in 0.1M acetate buffer solution (pH 4.5). The simultaneous determination of lead, cadmium and zinc was performed by square wave anodic stripping voltammetry. The Bi-CNT electrode presented well-defined, reproducible and sharp stripping signals. The peak current response increased linearly with the metal concentration in a range of 2-100 microg/L. The limit of detection was 1.3 microg/L for lead, 0.7 microg/L for cadmium and 12 microg/L for zinc (S/N=3). The Bi-CNT electrode was successfully applicable to analysis of trace metals in real environments.     

Hierarchical Porous Tubular Biochar Based Sensor for Detection of Trace Lead (II)

Hierarchical porous tubular biochar (PTBC) was prepared by selectively removing lignin simply according to reverse the pyrolysis sequence of cellulose. The properties of the PTBC sample were characterized by XRD, SEM, TEM, Raman spectra, cyclic voltammetry and electrochemical impedance spectroscopy. The electrochemical performances of PTBC modified on the screen-printing electrode illustrated excellent detection of lead ions (lead (II)) in water with the linear range (0.5–120 μg/L) and the detection limit (0.02 μg/L) by in-situ bismuth film square wave anode stripping voltammetry.     

Lab‐on‐a‐Chip Sensor with Evaporated Bismuth Film Electrode for Anodic Stripping Voltammetry of Zinc

In this work, we report on the development of a lab‐on‐a‐chip electrochemical sensor that uses an evaporated bismuth electrode to detect zinc using square wave anodic stripping voltammetry. The microscale electrochemical cell consists of a bismuth working electrode, an integrated silver/silver chloride reference electrode, and a gold auxiliary electrode. The sensor exhibits a linear response in 0.1 M acetate buffer at pH 6 with zinc concentrations in the 1–30 μM range and a calculated detection limit of 60 nM. The sensor successfully detected zinc in a bovine serum extract and the results were corfirmed by independent AAS measurements. Our results demonstrate the advantageous qualities of this lab‐on‐a‐chip electrochemical sensor for clinical applications, which include small sample volume (µL scale), reduced cost, short response time and high accuracy at low concentrations of analyte.     

Cation-exchange separation of metals in dimethyl sulphoxide-aqueous hydrochloric acid media

The behaviour of bismuth, cadmium, copper, lead, silver, tin and zinc on a cation-exchange resin in a solvent system consisting of dimethyl sulphoxide, hydrochloric acid and water was studied. The distribution coefficients of these metal ions between liquid and resin were determined as functions of the concentration of dimethyl sulphoxide and of hydrochloric acid. On the basis of the distribution coefficients found, predictions were made as to the possibilities of separating these metals from mixtures. Such separations were confirmed experimentally for bismuth from lead, bismuth from copper, zinc from lead, lead from cadmium, silver from copper, silver from lead, lead from cadmium from zinc, bismuth from lead from zinc, and bismuth from zinc from copper.     

Electrochemical properties of silver–copper alloy microelectrodes for use in voltammetric field apparatus

Microelectrodes of silver–copper alloys have been evaluated for use in voltammetric analyses. Increased overpotential towards the hydrogen overvoltage reaction (HER) was found as a function of increased copper content in the silver. A study of oxidizing products by cyclic voltammetry (CV) in NaOH solution showed ten anodic and eight cathodic peaks which are described in the present paper. The behaviour of these alloy electrodes is somewhere between pure silver and pure copper electrodes. Differential pulse anodic stripping voltammetry (DPASV) was used to measure zinc, cadmium and lead in ultrapure water only (18 MΩcm), and good linearity was found for all metals (r ²=0.998) in the range of 0.5 to 5 ppb with a 600- to 1,200-s plating time. It was additionally found that cadmium and lead were better separated on the alloy electrodes compared to pure silver electrodes. Measurements of nickel were carried out on alloy electrodes by use of adsorptive differential pulse cathodic stripping voltammetry (Ad-DPCSV), and good linearity (r ²=1.000) was found in the range from 0.5 to 5 ppb with an adsorption time of 120 s. The alloy electrodes were also found to be sensitive to nitrate, and good linearity (r ²=0.997) was found in the range from 1 mg L⁻¹ to 100 mg L⁻¹ using differential pulse voltammetry (DPV) scanning from −450 mV to −1,500 mV. Addition of nitrate in ultrapure water afforded two different peaks related to the successive reductions of nitrate and nitrite. In ammonium buffer solution (pH 8.6) only one peak resulting from reduction of nitrate was observed. Furthermore, the use of alloy electrodes containing 17% Cu was tested in real samples, by installing it in a voltammetric system for monitoring of zinc and lead in a polluted river, the river Deûle, near the town of Douai in northern France. Results were found to be in agreement with parallel measurements carried out by ICP-MS.     

Amalgam Electrodes for Electroanalysis

Liquid mercury is a unique material for the indicator electrode in voltammetry. One reason for this is the high overvoltage for hydrogen formation, thus extending the actual potential window. Diluted amalgams are important reaction products in voltammetric (polarographic) processes, however liquid amalgams are rarely used directly as electrode material for analytical purposes. Because of the fact that voltammetry is very suitable for field and remote monitoring, issues concerning the use of mercury electrodes in environmental analyses have led to considerable research effort aimed at finding alternative tools with acceptable performance. Solid electrodes are such alternatives. Different types of electrodes are reviewed. In particular, solid amalgam electrodes are very promising, with acceptable low toxicity to be used for field measurements. Solid amalgam electrodes are easy and cheap to construct and are stable over a reasonable time up to several weeks. Assessment of the toxicity risk and the long time stability for remote and unattended monitoring is discussed. The differences between solid dental amalgam electrodes, made by using techniques known from dental clinical practice, and mercury film or mercury layer electrodes on solid substrates are reviewed. In particular the dental technique for constructing solid amalgam electrodes gives advantage because it's fast and inexpensive. Also the technique for making dental amalgam has been explored and optimized over years by dentists, giving advantage when the same technique is used for constructing electrodes. Dental amalgam electrodes has been found to act similar to a silver electrodes, but with high overvoltage towards hydrogen. This make it possible to use the dental amalgam electrode for detection of zinc, cobalt and nickel in additions to other metals like lead, copper, thallium, cadmium, bismuth, iron etc. Also the use for reducible organic compounds is expected to be promising.     

Silver based mercury film electrode: Part II. The influence of aging of electrode on the electrode processes of various metal ions

The cyclic voltammetric behaviour of 8 metal ions at solid silver amalgam electrodes prepared by aging of a thin silver based mercury film electrode (SBMFE) and by deposition of silver and mercury on platinum were investigated. It was established that such electrodes behave in relation to some metals (Pb, Bi, Sn) similarly as silver electrodes i.e. the cyclic curves obtained with these electrodes at concentration 10^?3M range show a prepeak-postpeak system corresponding to deposition and dissolution of the monolayer of deposit. On the other hand under the same conditions no prepeaks were observed for cadmium, zinc and thallium. In all cases investigated the heights of anodic stripping peaks were lower on curves obtained with aged SBMFE than on those obtained with fresh SBMFE having a mercury layer 1 μm thick.     

A Multiple Evaluation Approach of Commercially Available Screen‐Printed Nanostructured Carbon Electrodes

Commercially available carbon‐based screen‐printed electrodes were studied by cyclic voltammetry and electrochemical impedance spectroscopy in their behavior towards electron transfer to the soluble fast redox probes hexacyanoferrate(III), hexaammineruthenium(III) and methyl‐viologen. Semi‐infinite linear diffusion was observed for hexacyanoferrate(III) probe, with heterogeneous electron transfer rate constants significantly favored on nanotubes‐modified surfaces. Finite diffusion was observed for methyl‐viologen on graphene electrodes, which was reflected in the enhancement of the faradic currents by 4‐folds. Hexaammineruthenium(III) showed mixed diffusion behavior. These characteristics are reflected in the voltammetric behavior of lead(II) and cadmium(II) stripping from in‐situ deposited bismuth layer.     

Electrochemical Characterization of and Stripping Voltammetry at Screen Printed Electrodes Modified with Different Brands of Multiwall Carbon Nanotubes and Bismuth Films

A screen-printed electrode sensor has been fabricated by modifying the carbon ink surface with different brands of multiwall carbon nanotubes (MWCNTs) and bismuth film (BiF) for the determination of traces of lead, cadmium and zinc ions by square wave anodic stripping voltammetry. The MWCNTs, from three different sources, were functionalized and dispersed in Nafion (MWCNT-Nafion) solution and placed on screen printed electrodes (MWCNT-Nafion/SPE); bismuth films were then prepared by ex-situ plating of bismuth onto the MWCNT-Nafion/SPE electrodes. The electrochemical characteristics of BiF/MWCNT-Nafion/SPE/ were examined by electrochemical impedance spectroscopy and showed differences; the charge transfer resistance tends to decrease with negative applied potentials. After optimizing the experimental conditions, the square-wave peak current signal is linear in the nmol L^?1 range. The lowest limit of detection found for the separate determination of lead, cadmium and zinc were 0.7 nmol L^?1, 1.5 nmol L^?1, and 11.1 nmol L^?1, respectively, with a 120 s deposition time.     

The Use of the Bismuth Film Electrode for the Anodic Stripping Voltammetric Determination of Tin

Bismuth coated glassy carbon electrodes have been applied to the square‐wave anodic stripping voltammetry (SWASV) of trace concentrations of tin. Optimization of Bismuth Film Electrode (BFE) performance was conducted after initial comparison with the more traditional mercury electrode. Simultaneous deposition of tin and bismuth at ?1.3 V for 2 minutes in a supporting electrolyte of 2.5 M sodium bromide utilizing a square‐wave stripping step, allowed analysis of tin at the μg L^?1 level. Parameters, such as deposition potential and time, bismuth concentration, square‐waveform settings including amplitude, step height and frequency were studied and optimized. The dependence of stripping current on deposition time indicates that using longer deposition time should facilitate sub μg L^?1 analysis. Tin was analyzed simultaneously with cadmium and either indium or thallium; Where as lead and copper were not resolved from the stripping peaks of tin and bismuth respectively. Finally, the method was applied to the analysis of tin in fruit juice.     

Voltammetry of lead cations on a new type of silver composite electrode in the presence of other cations

A new type of silver composite electrode was examined, prepared from silver, graphite powder, and methacrylate resin. The effects of the presence of various cations (cadmium, copper, bismuth, thallium), anions (chlorides), surface-active substances (Triton X-100), and oxygen on the anodic-stripping voltammetric determination of lead were studied. It was found that the effect of underpotential deposition at the composite electrode differs from that produced at a metallic silver electrode, mainly at low concentrations of the deposited metal. The use of this type of silver composite electrode in differential pulse anodic-stripping voltammetry enables direct determination of lead in natural water samples without elimination of surface-active substances (LOD about 3 g L^–1).     

Assessment of Lead and Cadmium in Canned Foods by Square-Wave Anodic Stripping Voltammetry

Abstract

This work reports the simultaneous determination of lead and cadmium in canned foods samples using square-wave anodic striping voltammetry (SWASV) on a bismuth film electrode (BiFE). The metal ions and bismuth were simultaneously deposited by reduction at ?1 V on a rotating carbon-paste disk electrode. Then, the preconcentrated metals were oxidized by scanning the potential of the electrode from ?1 to ?0.4 V using a square-wave waveform. The electrode displayed excellent linear behavior in the examined concentration range, from 5 to 150 µg/L of cadmium and lead (r² = 0.999 for both). Using the optimized conditions, the limits of detection were 0.27 µg/L for cadmium and 0.35 µg/L for lead. The reproducibility of the proposed sensor, evaluated in terms of relative standard deviation (RSD), were 5.8% and 3.7% of Cd and Pb, respectively for five measurements. Finally, the system based on BiFEs combined with rotating disk electrode was applied to determination of lead and cadmium in canned food samples. The results obtained were validated by inductively coupled plasma optical emission spectroscopy (ICP-OES).     

利用碘离子增感效应和金电极导数阳极溶出法研究铜丶铅和镉的同时测定

A method of simultaneous determination of copper (II), lead (II) and cadmium (II) in sulphuric acid-iocide ion medium was established by derivative anodic stripping voltammetry (DASV) on the gold electrode. The peak theights of lead and cadmium were increased by enhancement effect of iodide ion and the peaks of bismuth and copper were well formed and completely resolved on gold electrode in the presence of iodide ion, therefore peak of copper is not affected by bismuth. The sensitivities for copper, lead and cadmium were very high and their peak potentials in the stripping voltammogram were +0.25, -0.2 and -0.27 volt, respectively. The dependence of peak height of these elemets on their concentrations was linear. The detection limits for copper, lead and cadmium were 0.2 0.2 and 0.05 ppb, respectively. We have further studied the electrode process by means of triangle cyclic voltammetry and proved that he electrode reaction of copper is reversible, and that the reversibility of electrode reactions of lead and cadmium is not good.     

Determination of Thallium at A Silver‐Gold Alloy Electrode by Voltammetric Methods in Plant Material and Bottom Sediment Containing Cd and Pb

The applicability of the subtractive anodic stripping voltammetry (SASV) using the square‐wave mode at the silver‐gold alloy electrode has been studied for thallium determination in the presence of large amount of lead and cadmium in natural samples. 10 mmol L^?1 perchloric acid was found as the most suitable supporting electrolyte for determination in synthetic solutions. The thallium peak was separated about 200 mV from Cd+Pb peak. Diethylenetriaminepentaacetic acid addition was necessary to determine thallium at the silver‐gold alloy electrode in digested plant and sediment. The determination limit was equal to 1.4 μg L^?1. The method was validated by the inter‐method comparison (ICP‐MS).     

铋膜修饰玻碳电极伏安法测定微量铅(Ⅱ)

以铋膜修饰玻碳电极为工作电极,采用阳极溶出伏安法对微量Pb(Ⅱ)进行测定。考察了铋离子浓度、支持电解质pH、沉积时间等因素对测定的影响。实验结果表明,铋膜修饰电极对痕量Pb(Ⅱ)具有良好的电化学响应。在实验选定条件下,Pb(Ⅱ)在10～260!g/L范围内与峰电流呈良好的线性关系,检出限为1.98!g/L。用同一支铋膜电极对50!g/L Pb(Ⅱ)平行测定10次,相对标准偏差(RSD)为2.82%。该电极可应用于井水中铅的测定。