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.     

Siloxane‐Crown Ether Polyamide Based Electrode for Electrochemical Determination of Lead(II) in Aqueous Solution

A siloxane‐crown ether polyamide copolymer (PDMS‐PA‐DB18C6) was electrochemically investigated for fabrication of lead‐sensitive electrodes for trace analysis in aqueous solutions. The PDMS‐PA‐DB18C6 electrodes were successfully evaluated for anodic stripping voltammetric determination of lead(II) as a promising alternative for the detection of lead at ppb levels. By a judicious choice of the deposition time, electrolyte concentration and pulse amplitude, good analytical performance of the developed sensor could be achieved, with a linear response in the range of 20–700 ppb, when LOD of 3.5 ppb could be attained. This method showed a good degree of selectivity and sensitivity for lead, suitable for the determination of Pb²⁺ in wastewater sample.     

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.     

Anodic Stripping Potentiometric Determination of Cu,Pb, Cd and Zn In Natural Waters on a Novel Combined Electrode System

Abstract

A method is described for the reliable determination of copper, lead, cadmium and zinc in natural waters by anodic stripping potentiometry with the use of a novel combined electrode. The method involves two stripping cycles during which copper is initially determined on its own, followed by simultaneous determination of lead, cadmium and zinc after addition of gallium (III) ions. The optimum conditions include 0.01 M HCl as supporting electrolyte, 10 mg/L Hg (II) as chemical oxidant; E_dep(Cu) -700 mV vs Ag/AgCl; E_{dep(Pb,Cd,Zn)} -1200 mV vs Ag/AgCl; t_dep 10s; 150 μg/L Ga (III); sample rotation rate 5 and rest period 30s. Under these conditions, as low as 0.06 μg/L Cu (0.7% RSD); 0.2 μg/L Pb (13% RSD); 0.04 μg/L Cd (7.8% RSD) and 0.06 μg/L Zn (5.5% RSD) can be determined reliably. A linear concentration range of 0–110 μg/L was obtained for the four metals. The successful application of the method to reference fresh water, creek water and tap water is demonstrated.     

溶出伏安法测定乌药中的铜铅镉

在KNO3底液下,用线性扫描阳极溶出伏安法同时测定了乌药样品中铜、铅、镉3种金属的含量.结果表明,在最佳实验条件下,铜、铅、镉的峰电位分别为0.067、-0.45和-0.64V(vs ScE);铜、铅、镉金属离子的质量浓度在0-0.8 mg·L-1范围内,呈现良好的线性关系,相关系数分别为0.991 3、0.990 5...     

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).     

聚赖氨酸/多壁碳纳米管修饰电极测定大米中的铅

通过滴涂及电聚合方式分别将多壁碳纳米管和赖氨酸共修饰于玻碳电极上,制备出聚赖氨酸/多壁碳纳米管修饰电极,并建立了阳极溶出伏安法测定铅离子的新方法。采用线性扫描伏安法及循环伏安法研究了铅离子在修饰电极上的电化学行为,并考察了测定底液、底液p H值、富集电位、富集时间等条件的影响。在最佳实验条件下,铅离子的溶出峰电流与其浓度在2.0×10-7~8.0×10-5mol·L-1范围内呈良好的线性关系,检出限为1.0×10-7mol·L-1。利用所制备的修饰电极对大米样品进行加标回收实验,回收率为98%~102%。该方法具有良好的灵敏度和稳定性,已成功应用于大米样品中铅离子的测定。     

The determination of lead,copper and cadmium by anodic stripping voltammetry at a mercury thin-film electrode

The determination of lead, copper and cadmium by anodic stripping voltammetry at a wax-impregnated graphite electrode, pre-plated with mercury, has been investigated. Electrode preparation and cell design are discussed, and the effects of mercury loading and sample pH on electrode sensitivity are described. Detection limits and precision on aqueous samples are reported. Calibration graphs are linear for lead and cadmium, but non-linear for low concentrations of copper. The depression of peak current and shift of peak potential for copper in chloride media are described and an explanation is proposed. Precision and recovery of metal additions are reported for digested samples of whole blood.     

Electrochemical stripping determination of traces of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide

Procedures have been developed for the determination of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide, at concentrations of 1 ppm or less. Zirconium metal was dissolved in suphuric acid, and zirconium dioxide decomposed under pressure with hydrofluoric acid. Sample solutions were prepared in dilute sulphuric acid. For the stripping determination, the sample solution was either mixed with a complexing tartrate base electrolyte or the pre-electrolysis was carried out in acid solution, with the acid solution being exchanged for a pure base electrolyte (e.g. an acetate buffer) for the stripping step. The stripping step was monitored by d.c., differential pulse and Kalousek commutator voltammetry and the three methods were compared. A stationary mercury-drop electrode can generally be used for all the methods, whereas a mercury-film electrode is suitable only for the d.c. voltammetric determination of copper, lead and cadmium, as pulse measurements with films are poorly reproducible and the electrodes are easily damaged. The relative standard deviation does not exceed 20%. Some samples contained relatively large amounts of copper, which is best separated by electrodeposition on a platinum electrode.     

Electrodeposition and stripping of zinc from an ionic liquid polymer gel electrolyte for rechargeable zinc-based batteries

In this paper, we report on zinc deposition and stripping in an ionic liquid polymer gel electrolyte on gold and copper substrates, respectively. The ionic liquid-based polymer gel electrolyte is prepared by combining the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py_1,4]TfO), with Zn(TfO)₂ and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP). The ionic liquid polymer gel electrolyte exhibits good conductivity (2.2 mS cm^?1) and good mechanical stability. Zinc deposition and stripping in the ionic liquid polymer gel electrolyte were studied by cyclic voltammetry, potentiostatic, and galvanostatic cycling (charging/discharging) experiments. The gel electrolyte exhibits a promising electrochemical stability and allows a quasi-reversible zinc deposition/stripping. The morphology of the zinc deposits after 10 cycles of zinc deposition/stripping is compact and dense, and deposits without any dendrite formation can be obtained. The quasi-reversibility of the electrochemical deposition/stripping of zinc in this ionic liquid polymer gel electrolyte is of interest for rechargeable zinc-based batteries.     

Contribution of migration current to the voltammetric deposition and stripping of lead with and without added supporting electrolyte at a mercury-free carbon fibre microdisc electrode

In order to assess the contribution and analytical significance of migration, electrochemical studies on the deposition and stripping of lead at a carbon fibre microelectrode (diameter of 10 μm) have been undertaken in aqueous solutions containing 1 mM lead ions with variable KNO₃ supporting electrolyte concentrations (10⁻¹ to 10⁻⁵ M), as well as in the total absence of deliberately added supporting electrolyte. The methodology involved the application of cyclic voltammetry to characterise the Pb²⁺ (solution)+2e⁻Pb (metal) process in both the reduction (Pb deposition) and stripping (Pb dissolution) directions. The use of a mercury-free carbon surfaces means that the lead stripping does not occur from the amalgam state, as is commonly the case in anodic stripping voltammetry. In the deposition step, the current rises sharply with potential in response to a lead nucleation-growth process and then reaches an almost potential independent limiting value. The stripping step, obtained on the reverse scan, exhibited oxidation peak currents resulting from the redissolution or stripping of the metal from the electrode surface. The influence of the electrolyte concentration and hence migration current at −0.8 V versus Ag/AgCl for the deposition process, as well on the redissolution peak current and the dependence of the voltammograms on scan rate (10–1000 mV) are discussed. Interestingly, neither deposition limiting nor stripping peak currents vary in a simple manner with added supporting electrolyte concentrations, with maximum values being observed at 10⁻⁵ M rather than zero concentration of added KNO₃. An important implication for the voltammetric determination of lead in low ionic strength media by the very sensitive technique of anodic stripping voltammetry is that use of the method of standard additions commonly employed to minimise unknown matrix problems, is prone to error when contributions to the process from migration current are important.     

Anodic stripping voltammetry with medium exchange in trace element speciation

The application of medium exchange in anodic stripping voltammetry (ASV) was investigated by determing the fractions of ASV-labile copper, lead, cadmium and zinc in the presence of a variety of natural and sysnthetic ligands in a soft water. Pristin and polluted samples of river water were also tested. Medium exchange, where the test solution is replaced after electrodeposition by a simple electrolyte such as acetate buffer, before the oxidation (stripping) of the deposited metals, can ensure that the ASV-labile metal fraction depends only on the parameters of the electrodeposition step. Significant differences were found for ASV-labile fractons when medium exchange was used for the two river water samples, and for several mertal/ligand combinations such as copper/chloride, copper/humic acid, and zinc/tannic aid. It is recommended that medium exchange be used routinely for ASV-labile determinations.     

Copper Complexation with Soluble and Surface Freshwaters Ligands

Speciation of copper has been done using samples collected at different times of the year (December 92 and October 93) and in three sites of a polluted river (Este River, Northern Portugal). Filtered samples and the suspended particulate matter were titrated with metal ion and the labile metal concentrations measured by anodic stripping voltammetry (DPASV). An extra peak in the Cu voltammograms has been noticed when titrating filtered samples and its origin was investigated. Results have suggested that the extra peak is due to copper(I) stabilized by ligands adsorbed on the mercury electrode and a model for the electrochemical mechanism is proposed. From titrations of the same samples with zinc, cadmium and lead it has been concluded that there are two types of organics in the river water: macromolecules and small molecules with D_ML≈D_M with higher affinity for soft cations such as Cd(II) and Cu(I), that can be adsorbed on mercury electrode as anions.     

Stripping voltammetric determination of mercury(II) at antimony-coated carbon paste electrode

A new procedure was elaborated to determine mercury(II) using an anodic stripping square-wave voltammetry at the antimony film carbon paste electrode (SbF-CPE). In highly acidic medium of 1 M hydrochloric acid, voltammetric measurements can be realized in a wide potential window. Presence of cadmium(II) allows to separate peaks of Hg(II) and Sb(III) and apparently catalyses reoxidation of electrolytically accumulated mercury, thus allowing its determination at ppb levels. Calibration dependence was linear up to 100 ppb Hg with a detection limit of 1.3 ppb. Applicability of the method was tested on the real river water sample.     

Determination of mobile form contents of Zn, Cd, Pb and Cu in soil extracts by combined stripping voltammetry

The amount of mobile forms of Zn, Pb, Cd and Cu in extracts obtained by treating soil samples with ammonium nitrate were determined by an appropriate combination of anodic and cathodic stripping voltammetry with hanging mercury drop electrode. Every analysis required three mercury drops: on the first one, zinc was determined; on the second, cadmium and lead; on the third, copper was determined. Zinc, lead and cadmium were determined by conventional differential-pulse anodic stripping voltammetry. For copper determination, adsorptive differential-pulse cathodic stripping voltammetry with amalgamation using chloride ions as a complexing agent was applied. The standard deviation of the results was from 1 to 10% depending on the metal content in the sample. Voltammetric results were in good agreement with the AAS analysis. No microwave digestion of soil extracts was necessary.     

Selenomethionine‐Catalyzed Nickel Ion Reduction at a Mercury Electrode: Applications in the Analysis of Nutritional Supplements

Selenomethionine (SeMet) is a catalyst for Ni²⁺ reduction at a mercury electrode in a borax buffer at pH around 9 and gives rise to a differential pulse voltammetric peak, A, at ?0.74 V vs. the Ag|AgCl, (3 M KCl) reference electrode. Peak current is directly proportional to SeMet concentration over the concentration range 0.4–10 μM. Alkali and alkali‐earth ions depress to some extent the sensitivity but the current‐concentration relationships remains linear even under these conditions. Differential pulse cathodic stripping voltammetry (DPCSV) in 0.01 M borax results in two partially overlapped peaks. The more negative (A, at about ?0.74 V) is similar to that recorded with no deposition and is due to the catalysis by nonadsorbed SeMet, whereas the more positive one (B, at about ?0.60 V) results from the catalysis by adsorbed SeMet. Only the DPCSV peak A appears if 0.1 M KNO₃ is also present along with 0.01 M borax. Stearic acid, which is present in nutritional supplement tablets, improves the separation of the DPCSV peaks. Consequently, the peak B recorded with 0.01 M borax buffer allows determining SeMet in nutritional supplement tablets by the standard addition method and enables discriminating between the organic and inorganic selenium forms.     

Determination of copper ion by square wave anodic stripping voltammetry at antimony trioxide-modified carbon nanotube paste electrode

In this work, an antimony trioxide-modified multi-walled carbon nanotube paste electrode (Sb₂O₃/CNTPE) was employed for determination of Cu²⁺ ions by using square wave anodic stripping voltammetry (SWASV) in the presence of 8-hydroxy-7-iodo-5-quinoline sulfonic acid (HIQSA) as a chelating agent. The field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS) methods were applied to estimate the morphology and properties of the modified electrode. Measurements related to SWASV were taken in 0.6 M HCl at ?1.0 V versus Ag|AgCl|KCl (3 M) for 90 s (deposition step). After equilibrium time of 15 s, an ASV appeared at 0.0 V versus Ag|AgCl|KCl (3 M) (stripping step). The sensor depicted a fairly linear response for Cu²⁺ in the concentration range of 2–100 ppb with appropriate detection limit about 0.39 ppb and limit of quantification about 1.3 ppb. The stability of the modified electrode during 7 weeks and its behavior in the presence of some metal ions was evaluated. The practical applicability of the Sb₂O₃/CNTPE was established on the voltammetric determination of Cu²⁺ in tap water as a sample.     

Anodic stripping voltammetry and chronopotentiometry of copper at a rotating carbosital disk electrode

The use of a new carbon material — carbosital — for electrodes is reviewed. The behaviour of copper deposited on the carbosital electrode surface in anodic stripping voltammetry and chronopotentiometry is discussed. In anodic stripping voltammetry with a rotating carbosital disk electrode, the peak current and the number of coulombs involved in stripping copper are directly proportional to the square root of the electrode rotation rate during preelectroiysis; the peak current is directly proportional to the potential scan rate during stripping. For anodic stripping voltammetry and anodic stripping chronopotentiometry, linear calibration graphs are obtained in the range 1 X 10^-3–1 x 10^-6 M copper(II). The method is applicable to analysis of high-purity cadmium for copper.     

Microliter Volume Determination of Cosmetic Mercury with a Partially Crosslinked Poly(4‐vinylpyridine) Modified Screen‐Printed Three‐Electrode Portable Assembly

We successfully demonstrated microliter (μL) volume determination of Mercury (Hg) using an in‐built screen‐printed three electrodes containing partially crosslinked poly(4‐vinlylpyridine) (designated as pcPVP) modified carbon‐working, carbon‐counter, and Ag⁺‐quasireference electrodes (SPE/pcPVP) in a pH 4 acetate buffer solution with 2 M KCl by using the square wave anodic stripping voltammetric (SWASV) technique. Instrumental and solution phase conditions were systematically optimized. Experiments were carried out by simply placing a 500 μL‐droplet of Hg containing real sample mixed with the base electrolyte on the SPE/pcPVP surface. The SPE/Ag⁺ quasi‐reference system shifted the Hg‐SWASV detection potential ca. 250 mV positive, but the quantitative current values were appreciably similar to that of a standard Ag/AgCl reference electrode. Under optimal condition, the calibration graph is linear in the window of 100–1000 ppb of the Hg droplet system with a detection limit of 69.5 ppb (S/N=3). Finally real sample assays were demonstrated for prohibited cosmetic Hg containing skin‐lightening agents in parallel with ICP‐OES measurements.     

Stripping chronopotentiometric detection of copper using screen-printed three-electrode system—application to acetic-acid bioavailable fraction from soil samples

Single-use sensors, incorporating a three-electrode configuration (graphite carbon-working electrode; carbon-counter electrode and silver/silver chloride-reference electrode), have been fabricated on a polyester substrate using low cost screen-printing (thick-film) technology. These electrodes coupled with constant current stripping chronopotentiometry (CCSCP), has provided a convenient screening tool for on-site detection of trace levels of copper. Modification of the graphite carbon surface based on in situ deposition of mercury film has been carried out. By appropriate choice of supporting medium and applied constant stripping current, well-resolved and reproducible response for copper was obtained. The stripping response for copper following 2 min deposition was linear over the concentration range examined (10-2000 ppb) with detection limit of 6 ppb using 2 M hydrochloric acid (HCl). Successful applications of the sensing device to acetic-acid bioavailable fraction of a certified reference material (CRM 601, a lake sediment) and soil samples are demonstrated.