Voltammetric Determination Of Lead Research Articles

Voltammetric Determination of Lead and Copper in Wine by Modified Glassy Carbon Electrode

This paper describes the determination of Pb and Cu with a Nafion-modified glassy carbon electrode and MnCo2O4 nanoparticles as working electrode for anodic stripping voltammetry. Pb and Cu were accumulated in HCl/KCl (0.1 mol dm-3) at a potential of -1.4 V (vs. Ag/AgCl electrode) for 480 s, followed by a linear sweep anodic stripping voltammetry (ASV) scan from -1.0 to +0.5 V. Under optimum conditions, the calibration curves were linear in the range of 0.01 - 8 and 0.01 - 5 mg dm-3 for Pb and Cu, respectively. Effect of sample dilution, accumulation time and potential were optimized. A study of interfering substances was performed. A significant increase in current was obtained at the modified electrode in comparison with the bare glassy carbon electrode. The modified electrode was successfully applied for determination of Pb and Cu in wine samples after a simple preparation procedure. Pb and Cu content in wine was used for estimation of the target hazard quotient (THQ) values for minimal and maximal levels of the metals.

A novel electrochemical immobilization of Hg in CdSe QDs - modified graphite electrode and its improved performance in voltammetric determination of lead (II) ion

A novel metal ion sensor was fabricated through electrochemically immobilized Hg spheres on surface-unpassivated CdSe quantum dots modified paraffin wax impregnated graphite electrode. The size and surface morphology of the CdSe QDs and CdSe QDs - Hg modified electrode was characterized by transmission electron microscope and field emission scanning electron microscopy. The modified electrode was also characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The modified electrode was used for the determination of trace level lead ion which was preconcentrated onto the modified electrode by differential pulse anodic stripping voltammetry (DPASV). Numerous key variables affecting the current response of lead ion have been optimized. The proposed electrode has a linear concentration range of 5.2 ng/L–4.2 µg/L with a optimized deposition time of 180 s and the detection limit is found to be 1.7 ng/L (S/N = 3). The electroanalytical performance of the modified electrode was successfully tested in a real sample of tap water and sea water spiked with Pb(II) ion. The proposed electrode shows excellent selectivity and sensitivity over other heavy metals, such as copper, zinc, manganese and tin. Hg(II) immobilized CdSe QDs modified electrode has shown great potential application in detecting metal ions at very low concentrations.

Synthesis and application of a natural-based nanocomposite with carbon nanotubes for sensitive voltammetric determination of lead (II) ions

ABSTRACTA modified carbon paste electrode has been developed for the determination of Pb(ΙΙ) ions based on Fe3O4/eggshell magnetic nanocomposite. The structure and morphology of Fe3O4/eggshell were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The prepared nanocomposite was also characterized by Fourier transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The electrochemical procedure was based on the accumulation and determination of Pb(ΙΙ) ions at the surface of the modified carbon paste electrode with Fe3O4/eggshell nanocomposites and carbon nanotubes by differential pulse anodic stripping voltammetry (DPASV). Various experimental parameters involved in the preconcentration of Pb(ΙΙ) ions and voltammetric stripping step were studied. Under the optimum conditions, the voltammetric peak current of Pb(ΙΙ) occurs at a potential about −0.5 V. Also, the voltammetric peak current increased linearly with Pb(ΙΙ) concentration in the range of 0.5–200 ng mL−1 and a detection limit of 0.15 ng mL−1 was obtained for Pb(ΙΙ). The selectivity of the proposed electrode for Pb(ΙΙ) ions in the presence of some cations was also examined. The practical application of the proposed modified electrode was evaluated by the determination of Pb(ΙΙ) ions in human hair and water samples. The results were satisfactory for the spiked samples.

Voltammetric determination of lead and cadmium in vegetables by graphene paste electrode modified with activated carbon from coconut husk

A multilayer graphene paste electrode (MGPE), consisting of graphene flakes and mineral oil, was modified with activated carbon (AC). The AC was produced from coconut husk using zinc chloride as the activating agent. The AC/MGPE was fabricated by substituting an amount of the multilayer graphene (MG) with the AC, and the resulting paste was packed in a Teflon syringe. The electrode was used to simultaneously detect lead (Pb2+) and cadmium (Cd2+) via anodic stripping voltammetry (ASV). The amounts of MG and AC in the electrodes were varied by substituting the amount of the former with the latter (by percent) and the best electrode was found to consist of 5% AC and 95% MG. The optimal parameters, accumulation time, deposition time, and deposition potential were determined. The optimized parameters were used on the said best electrode to determine the calibration curve and limit of detection. The peak current had a linear relation with the concentration of the heavy metals with a correlation value (R2) of 0.9956 and 0.9973 for Cd2+ and Pb2+, respectively. After which the electrode was used to detect heavy metals in vegetable samples, and the results were verified via atomic absorption spectroscopy. The heavy metal concentrations that were detected in most of the samples were above the maximum limit as dictated by the World Health Organization.

Voltammetric determination of lead(II) by using exonuclease III and gold nanoparticles, and by exploiting the conformational change of the complementary strand of an aptamer

The authors describe an electrochemical aptasensing platform for the determination of Pb(II) ions. The assay is based on the use of gold nanoparticles (AuNPs) (that facilitate electron transfer), the enzyme exonuclease III (Exo III; assisting signal amplification), and a hairpin structured complementary strand of an aptamer that prevents binding of AuNPs to the surface of the sensor electrode in the presence of Pb(II). In the absence of Pb(II), AuNPs attach to the surface of the gold electrode, and this leads to a strong voltammetric signal. In the presence of Pb(II), however, the AuNPs do not bind to the surface of the electrode because of the hairpin structure of the complementary strand. As a result, the peak current (typically measured at 0.17 V vs. silver reference electrode) remains weak. The method has a 149 pM detection limit. It was applied to the analysis of spiked tap water and human serum samples and gave recoveries between 92 and 105.25%.

Development and application of potentiometric stripping analysis

This paper focuses on the voltammetric determination of lead, cadmium and zinc in water. Two ways of determining were investigated: individually and all three metals simultaneously. The experiments were performed using the Potentiometric Stripping Analysis (PSA). Determination of metals in real samples was preceded by preliminary tests. Preliminary investigations were performed in order to determine the optimal conditions of measurement. It was concluded that the process of determining was for most part influenced by: pH, time of metals extraction, stirring rate of the solution and the thickness of the mercury layer on the working electrode. The smallest concentrations of metals which can be determined using this method are: for lead 22.48 μg dm-3, for cadmium 16.23 μg dm-3 and for zinc 18.75 μg dm-3. The obtained results deviated from the actual 1.12% for lead, 1.91% for cadmium and 1.81% for zinc. All tests (individually and simultaneously) were conducted from model solution with concentration as follows: 44.96 μg dm-3 for lead, 32.47 μg dm-3 for cadmium and 37.50 μg dm-3 for zinc. The results of individual measurements deviated by 1.02% lead, 1.90% for cadmium and 1.89% for zinc. Simultaneously the contents were lower than real for: -4.58% for lead, cadmium for -1.91% and -1.89% for zinc. For the conditions determined, except for lead, deviations did not exceed ±2% . This indicates that Potentiometric Stripping Analysis is a good way of individual and simultaneous determination of lead, cadmium and zinc and for determination of their concentrations in water (river and groundwater).

An organically modified exfoliated graphite electrode for the voltammetric determination of lead ions in contaminated water samples

This work presents a new electrode, 2-benzoylnaphtho [2,1-b]furan hydrazone exfoliated graphite paste electrode (B-EGPE) fabricated for the differential pulse anodic stripping voltammetric determination of lead (Pb). Under the optimal conditions, Pb2+ could be detected in the concentration range from 2.75 × 10−7 to 1.5 × 10−6 mol/L with the linear regression equation, y = 19.41 × 10−6x + 0.4249 × 10−9 with R = 0.99. Interferences from other ions were investigated and the proposed method was further applied to the trace levels of Pb2+ detection in real samples with satisfactory results.

Determination of trace amounts of lead by adsorptive cathodic stripping voltammetry with L-3-(3,4-Dihydroxyphenyl)alanine

A sensitive and selective procedure is presented for the voltammetric determination of lead. The procedure involves an adsorptive accumulation of lead L-3-(3,4-dihydroxyphenyl)alanine (LDOPA) on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of reduction current of an adsorbed complex at –0.15 V (vs Ag|AgCl). Optimum conditions for lead analysis include pH 8.5, 80 μM LDOPA and accumulation potential –0.15 V (vs Ag|AgCl). The peak currents are proportional to the lead concentration 1–300 nmol l–1 with a detection limit of 0.6 nmol l–1 and accumulation time 60 s. The method was used for the determination of lead in blood, dry tea and also in waters.

Simultaneous Voltammetric Determination of Lead and Tin by Adsorptive Differential Pulse Stripping Method and Orthogonal Signal Correction‐Partial Least Squares in Water Samples

AbstractAn adsorptive differential pulse stripping method for the simultaneous determination of lead and tin is proposed. The procedure involves an adsorptive accumulation of lead and tin on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed lead and tin by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: 0.2 mol L−1 HNO3, accumulation potential of −900 mV versus Ag/AgCl, accumulation time of 200 s, scan rate of 20 mV s−1 and pulse height of 80 mV. Lead and tin peak currents were observed in the same potential region at about −400 mV. The simultaneous determination of lead and tin by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of a mixture of lead and tin by the application of orthogonal signal correction‐partial least squares (OSC‐PLS) was performed. The linear dynamic ranges were 0.003‐0.35 and 0.008‐0.50 μg mL−1 and detection limits were land 3 ng mL−1 for lead and tin, respectively. The RMSEP for lead and tin with OSC and without OSC were 2.8737, 6.0557 and 8.0941, 9.5151, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of lead and tin in water samples with satisfactory results.

Voltammetric Determination of Lead (II) Ions at Carbon Paste Electrode Modified with Banana Tissue

Voltammetric Determination of Lead (II) Ions at Carbon Paste Electrode Modified with Banana Tissue

Anodic stripping voltammetric determination of lead and cadmium in soil extracts

AbstractTwo single-step extraction procedures validated by BCR, extraction with 0.43 mol dm−3 acetic acid and 0.05 mol dm−3 EDTA, are used for assessing bioavailable species of Pb and Cd in soils. After an extensive study of interferences of humic substances and using standard additions procedures, the extractable contents of Pb and Cd have been determined by DPASV directly in soil extracts with a good reproducibility (RSD varied from 1.0 to 7.9 %). Pb(II) and Cd(II) were released from complex in EDTA extracts by pH adjustment to 1 with 1 mol dm−3 HCl. The results were compared with those obtained with atomic absorption spectrometry and indicated reasonable agreement of both methods. Exchangeable forms represented 0.2 to 3.3 % and 13.0 to 63.6 % of total content of Pb and Cd in soils, respectively. EDTA extraction released from soils 7.9 to 29.9 % and 33.5 to 59.6 % of total content of Pb and Cd, respectively.

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 microg L(-1)).

Voltammetric determination of lead at chemically modified electrodes based on crown ethers.

The feasibility of fabricating lead-sensitive chemically modified electrodes (CMEs) for trace analysis in aqueous and 40% (v/v) ethanol-water media was investigated. Carbon paste electrodes modified with crown ethers were constructed by mixing the crown ethers into a graphite powder-paraffin oil matrix. The thus-formed electrodes were able to bind Pb(II) ions chemically, and gave better voltammetric responses than unmodified ones. The crown ethers studied and compared were 18-crown-6 and dibenzo-18-crown-6. With a 5% 18-crown-6 CME, Pb(II) could be quantified at sub-ppm levels by differential pulse voltammetry with a detection limit of 0.02 ppm. It was possible to selectively pick up Pb(II) from a solution of several other ions at an open circuit through complexation. A simultaneous analysis of Cu(II) and Pb(II) was also attempted. By differential pulse anodic stripping voltammetry Pb(II) could be quantified over the range of 1 to 100 ppb. Interference from metal ions like Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Ag(I), Fe(III), Ca(II) and Mg(II) was also studied. The method was successfully applied to artificial as well as commercial samples of alcoholic beverages.

Stability of mercury film electrodes under the influence of high frequency (500 kHz) ultrasound

The analytical utility of coupling high frequency ultrasound (500 kHz) systems with electrochemical stripping techniques has been investigated. The stability of mercury film electrodes (on either glassy carbon or iridium substrates) under various ultrasound regimes was assessed with cavitational erosion found to occur irrespective of the substrate or position within the cell assembly. Removal of dissolved gas was found to increase the lifetime of the mercury film but only through sacrificing enhancements in mass transport. A second series of experiments investigated the influence of ultrasound frequency (20 and 500 kHz) on the stripping voltammetric determination of lead and cadmium at bare glassy carbon electrodes. The results were compared with silent conditions with the high frequency system shown to significantly enhance the accumulation of the target analyte.

Stripping voltammetric determination of lead using a glassy-carbon electrode system

The effect of the electrochemical pretreatment of the surface of a glassy-carbon indicator electrode on the electrode response and the repeatability of measurements in the stripping voltammetric determination of lead was studied. It was shown that the analytical signal depends on the nature of an electrolyte used for the pretreatment. The electrolytes that gave the most satisfactory results in the pretreatment were proposed

Simultaneous anodic stripping voltammetric determination of lead and cadmium with a carbon paste electrode modified by tributyl phosphate

A chemically modified carbon paste electrode was prepared by incorporating quantities of tributyl phosphate (TBP) directly into the paste mixture. In the presence of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), trace lead and cadmium in acetic acid-acetate medium can be preconcentrated on the electrode. The method showed good linearly for 1.0 × 10−8 − 8.0 × 10−7 mol·L−1 lead(II) and for 5.0 × 10−8 − 2.0 × 10−6 mol·L−1 cadmium(II). Many common metal ions have no or little effect on the determination of lead(II) and cadmium(II). The electrode was verified by the determination of trace lead(II) and cadmium(II) in waste water and human hair samples.

Voltammetric determination of lead, cadmium and copper traces in ammonium fluoride.

A rapid and precise voltammetric method for the determination of traces of Pb, Cd and Cu in NH(4)F has been developed based on the capability of boric acid to mask fluoride ions and on the measurement of the analyte signals of the blank and the sample in the same solution.

Voltammetric determination of lead with a chemically modified carbon paste electrode with diphenylthiocarbazone

A carbon paste electrode modified with dithizone (diphenylthiocarbazone) was employed for quantification of lead from aqueous solutions. Lead(II) was chemically deposited on the chemically modified electrode (CME) by complexation with the modifier, and the electrode was transferred to an electrochemical cell for pulse voltammetric anodic stripping. The response depends on the concentration of lead in the bulk solution as well as the parameters involved in both the preconcentration and the measurement steps. For a 6-min preconcentration time, the calibration graph is linear from 20.7 ng ml −1 to 207.2 ng ml −1 and from 207.2 ng ml −1 to 518.0 ng ml −1. The detection limit (DL, 3σ) was about 16.7 ng ml −1 and the response could be reproduced with a 5.8% relative standard deviation at the concentration level of 31.1 ng ml −1. Interferences by metal ions which compete for complexation with the modifier on the CME surface could be eliminated by using masking reagents. Strong complexing agents, such as sulphide, interfere. The method was used for the determination of lead in natural waters.

Rapid sample preparation and voltammetric determination of lead, cadmium and copper traces in calcium fluoride

An improved method is described for the voltammetric determination of Pb, Cd and Cu in calcium fluoride. A shortening of the time required has been achieved by omitting the removal of the fluoride ions and by measuring blank and sample signals in one and the same solution (before and after adding CaF2). The results were in satisfactory agreement with those obtained by other methods.

Voltammetric Determination of Lead as Lead Dioxide at the Rotated Platinum Wire Electrode

Voltammetric Determination of Lead as Lead Dioxide at the Rotated Platinum Wire Electrode