Search

Entomotoxicology allows the detection and analysis of substances such as poisons, drugs, and metals in necrophagous insects using analytical protocols. In a forensic situation related to death by gunshot, the gunshot residue (GSR) is dispersed at the crime scene and may be consumed by necrophagous insects. Lead (Pb) is the most abundant metal in GSR samples and it can be determined using non-portable methods. However, the toxicity effects of GSR samples on Lucilia cuprina (Diptera: Calliphoridae) and the detection of Pb via portable electrochemical methods have not been investigated. This study describes for the first time the toxicity analysis of Pb on immature L. cuprina through their survival rate and influence of Pb on immature development. In addition, the bioaccumulation of Pb in the larvae samples was determined based on square wave anodic stripping voltammetry (SWASV) measurements. The results revealed a low limit of detection to Pb (6.5 μg L -1 ) and the analytical performance was satisfactory because it measures Pb levels in larvae exposed to a diet containing 50 μg Pb g -1 . Furthermore, the levels of Pb influenced the survival rate and development time of the immature L. cuprina. Larvae exposed to a high concentration of the metal (50 μg Pb g -1 ) showed statistically significant changes (p < 0.05). The presence of Pb in immature L. cuprina can be used to estimate the post-mortem interval; thus, the present study provides important information in forensic entomology.

This paper describes the determination of Pb and Cu with a Nafion-modified glassy carbon electrode and MnCo 2 O 4 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.

The worm-like nitrogen-doped-carbon framework (WNCF) with abundant edge-plane-like defective sites (EDSs) was synthesized by using natural wax gourd (Benincasa hispida) as the main carbon precursor and milk yielded by Chinese Holstein cattle (Holstein Friesian) as the nitrogen precursor for the first time. The Nafion-dispersed WNCF (Nafion-WNCF) was employed to design a highly sensitive electrochemical sensor for the trace determination of toxic heavy metal lead (II) (Pb 2+ ) by the differential pulse anodic stripping voltammetry (DPASV). Some key experimental factors including calcination temperature of WNCF, pH value of the buffer solution, deposition potential, deposition time and the concentration of bismuth (Bi 3+ ) were optimized for the stripping analysis of Pb 2+ . Under the optimum experimental condition, Nafion-WNCF modified bismuth film glassy carbon electrode (Nafion-WNCF/BFGCE) exhibits a wide linear range from 0.5 μg L -1 to 100 μg L -1 and a low detection limit of 0.2 μg L -1  (S/N = 3) for detecting Pb 2+ . Especially, Nafion-WNCF/BFGCE was successfully applied to determine Pb 2+ in tap water and lake water samples. All the results suggest that the WNCF can be considered as a green and low-cost nanomaterial for the precision detection of Pb 2+ in real samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A facile electrochemical sandwich immunosensor for the detection of a breast cancer biomarker, the human epidermal growth factor receptor 2 (HER2), was designed, using lead sulfide quantum dots-conjugated secondary HER2 antibody (Ab2-PbS QDs) as a label. Using Ab2-PbS QDs in the development of electrochemical immunoassays leads to many advantages such as straightforward synthesis and well-defined stripping signal of Pb(II) through acid dissolution, which in turn yields better sensing performance for the sandwiched immunosensor. In the bioconjugation of PbS QDs, the available amine and hydroxyl groups from secondary anti-HER2 and capped PbS QDs were bound covalently together via carbonyldiimidazole (CDI) acting as a linker. In order to quantify the biomarker, SWV signal was obtained, where the Pb 2+ ions after acid dissolution in HCl was detected. The plated mercury film SPCE was also detected in situ. Under optimal conditions, HER2 was detected in a linear range from 1-100 ng/mL with a limit of detection of 0.28 ng/mL. The measures of satisfactory recoveries were 91.3% to 104.3% for the spiked samples, displaying high selectivity. Therefore, this method can be applied to determine HER2 in human serum., (Copyright © 2019. Published by Elsevier B.V.)

Here, we report for the first time, an electrochemical immunoassay to detect IgM antibodies using lead sulfide quantum dots (PbS QDs) as electrochemical labels. In this sense, dendritic-like polydopamine particles loaded with PbS QDs were synthesized by the self-polymerization of dopamine in basic media in the presence of QDs (PbS@PDA) and further tagged with anti-IgM antibodies, dengue specific antigens, and streptavidin moieties. The analytical features of the sandwich immunoassay on ELISA microplate were carried out with the PbS@PDA-labeled anti-IgM as secondary antibody. The system was interrogated by acid dissolution of PbS@PDA, followed by differential pulse anodic stripping voltammetry in the presence of Bi(III) ions using carbon screen-printed electrodes. The results indicate that the voltammetric current increased with the increasing of the concentration of target IgM within a range of 0-0.5 mg mL -1 . The limit of detection of this electrochemical immunoassay was evaluated to 130 ng. The measures of satisfactory recoveries from 88.5% to 114% of spiked samples indicate that such a method has good specificity and is applicable to the quantification of IgM antibodies in complex biological samples. No significant differences at the 0.05 significance level were encountered in the analysis of IgM samples between the electrochemical immunoassay and a Bradford assay., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This work reports the development of a glutathione modified electrode via electrografting on a screen-printed carbon nanofiber substrate (GSH-SPCNFE). GSH-SPCNFE was compared to a classical screen-printed carbon electrode modified with glutathione (GSH-SPCE) for the simultaneous voltammetric determination of Cd(II) and Pb(II). Their electrochemical characterization and analytical performance suggest that SPCNFE could be a much better support for GSH immobilization. The applicability of GSH-SPCNFE for the determination of low concentration levels of Pb(II) and Cd(II) ions in environmental samples was successfully tested in a certified wastewater reference material by means of stripping voltammetry with a very high reproducibility and good trueness., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A new penicillamine-GCE was developed based on the immobilization of d-penicillamine on aryl diazonium salt monolayers anchored to the glassy carbon electrode (GCE) surface and it was applied for the first time to the simultaneous determination of Cd(II) and Pb(II) ions by stripping voltammetric techniques. The detection and quantification limits at levels of µg L(-1) suggest that the penicillamine-GCE could be fully suitable for the determination of the considered ions in natural samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This work describes the immobilization of 4-carboxybenzo-18-crown-6 (CB-18-crown-6) and 4-carboxybenzo-15-crown-5 (CB-15-crown-5) assisted by lysine on aryl diazonium salt monolayers anchored to the surface of graphite-epoxy composite electrodes (GEC), and their use for the simultaneous determination of Cd(II), Pb(II) and Cu(II) by differential pulse anodic stripping voltammetry (DPASV). These modified electrodes display a good repeatability and reproducibility with detection and quantification limits at levels of µg L(-1) (ppb), confirming their suitability for the determination of Cd(II), Pb(II) and Cu(II) ions in environmental samples. The overlapped nature of the multimetal stripping measurements was resolved by employing the two-sensor array CB-15-crown-5-GEC and CB-18-crown-6-GEC, since the metal complex selectivity exhibited by the considered ligands could add some discrimination power. For the processing of the voltammograms, Discrete Wavelet Transform and Causal Index were selected as preprocessing tools for data compression coupled with an artificial neural network for the modeling of the obtained responses, allowing the resolution of mixtures of these metals with good prediction of their concentrations (correlation with expected values for an external test subset better than 0.942)., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This paper reports the development of three peptide modified sensors in which glutathione (GSH) and its fragments Cys-Gly and γ-Glu-Cys were immobilized respectively through aryl diazonium electrochemical grafting onto the surface of graphite-epoxy composite electrodes (GEC), and used for the simultaneous determination of Cd(II), Pb(II) and Zn(II). The concentration interval ranged from 0.1 to 1.5 μmol L(-1) for each metal, and the technique used was differential pulse adsorptive stripping voltammetry. This study aimed to the comparison of the information provided by one single modified electrode at both fixed and multiple pH values (pH 6.8, 7.5 and 8.2) for the simultaneous determination of the three metals, with those supplied by the three-sensor array at multiple pH values. For the processing of the voltammograms, the fast Fourier transform was selected as the preprocessing tool for data compression coupled with an artificial neural network for the modeling of the obtained responses., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A commercially available sputtered bismuth screen-printed electrode (BispSPE) has been pioneeringly applied for the simultaneous determination of Cd(II) and Pb(II) ions in a certified groundwater sample by means of differential pulse anodic stripping voltammetry (DPASV) as an alternative to more conventional bismuth screen-printed carbon electrodes (BiSPCEs). BispSPEs can be used for a large set of measurements without any previous plating or activation. The obtained detection and quantification limits suggest that BispSPEs produce a better analytical performance as compared to In-situ BiSPCE for Pb(II) and Cd(II) determination, but also to Ex-situ BiSPCE for Cd(II) determination. The results confirm the applicability of these devices for the determination of low level concentrations of these metal ions in natural samples with very high reproducibility (0.7% and 2.5% for Pb(II) and Cd(II) respectively), and good trueness (0.3% and 2.4% for Pb(II) and Cd(II) respectively)., (© 2013 Published by Elsevier B.V.)

Low cost disposable working electrodes are specifically desired for practical applications of electrochemical detection considering maturity of electrochemical stations and data collection protocols. In this paper double-sided conductive adhesive carbon tape with nanostructure was applied to fabricate disposable working electrodes. Being supported by indium tin oxide glass, the prepared carbon tape electrodes were coated with bismuth film for stripping analysis of heavy metal ions. By integrating the bismuth modified electrodes with paper-based analytical devices, we were able to differentiate Zn, Cd and Pb ions with the sample volume of around 15 μL. After the optimization of parameters, including modification of bismuth film and the area of the electrodes, etc., Pb ions could be measured in the linear range from 10 to 500 μg/L with the detection limit of 2 μg/L. Our experimental results revealed that the disposable modified electrodes could be used to quantify migrated lead from toys with the results agreed well with that using atomic absorption spectrometry. Although bismuth modification and stripping analysis could be influenced by the low conductivity of the carbon tape, the low cost disposable carbon tape electrodes take the advantages of large-scaled produced double-sided carbon tape, including its reproducible nanostructure and scaled-up fabrication process. In addition, the preparation of disposable electrodes avoids time-consuming pretreatment and experienced operation. This study implied that the carbon tape might be an alternative candidate for practical applications of electrochemical detection., (© 2013 Elsevier B.V. All rights reserved.)

In the present work, we report the synthesis and evaluation of a graphite-supported bismuth film working electrode (BiFE) in the simultaneous quantification of Hg(II) and Pb(II) at ppb levels. The BiFE was synthesized in-situ by electrodeposition in 1 M HNO3 as the supporting electrolyte at −0.5 V potential. A design of experiments and a response surface model (RSM) were developed to optimize the parameter of bismuth concentration ([Bi]) and deposition time (tdep) in the synthesis of the BiFE. The electrodeposition conditions of [Bi] = 3 mM and tdep = 10s proved to be the optimal conditions for the highest sensitivity and selectivity of the synthesized working electrode. For the quantification of Hg(II) and Pb(II), the electrochemical technique of square wave anodic stripping voltammetry (SWASV) was used by applying a deposition potential of −1 V in 1 M acetic acid buffer solution. The optimization of the factors analyzed in the design of experiments allowed the simultaneous detection of Hg(II) and Pb(II) at limiting levels of 1 ppb and 10 ppb, respectively. The calibration curves of Hg(II) and Pb(II) present an R2 of 0.988 and 0.982, respectively.

Stripping analysis was proposed for the voltammetric determination of trace cadmium and lead in local rice wine alcoholic beverages. A bismuth-antimony film electrode (Bi-SbFE) was employed for accumulative preconcentration of trace metals by adding 4 mg L−1 of bismuth and 1 mg L−1 of antimony directly to the sample solution and simultaneously depositing bismuth, antimony, and trace cadmium and lead target metals on the glassy carbon electrode by applying a fixed potential of –1.1 V versus the Ag/AgCl reference electrode for 300 s. Pre-treatment parameters for mineralization of the sample were optimized using the wet acid digestion procedure. Under the optimum conditions, linear calibration graphs ranging 20-200 μg L−1 for Cd and Pb were obtained with detection limits of 0.22 and 0.62 μg L−1 and limits of quantitation 0.73 and 2.07 μg L−1, respectively. Reproducibility values for seven replicate analyses of 50 μg L−1 Cd and Pb were 3.6 and 3.3%, respectively. The developed method was successful for Cd and Pb analyses in Thai rice wine samples and results were validated by the flame atomic absorption spectrometric method. Most samples were not contaminated with Cd and Pb. The amount of Cd contaminants in only one of rice wine sample was still lower than the maximum permitted level of Cd in wine.

The stripping voltammetry at HMDE is proposed for Cd and Pb (undesirable ingredients) determination in the natural brine (CCl >43 g L−1). Samples with so high salinity have to be significantly diluted. For ICP MS, a 105–6 times dilution is required, which disqualifies this method. The proposed procedure allows to determine Cd (0.001 μg L−1) and Pb (0.005 μg L−1) after only 100 times dilution. The thermal chloride stripping or isolation by Chelex 100 increase the quality of obtained data. The recovery study was performed. The LOQs are below recommendations related to the use of brines in balneology. [ABSTRACT FROM AUTHOR]

A copper film-modified, carboxyl-functionalized, and multi-walled carbon nanotube (MWCNT-COOH)-modified screen-printed carbon electrode (CuF/MWCNTs/SPCE) was used for lead determination using anodic stripping voltammetry. The main parameters were investigated and optimized during the development of the research procedure. The most optimal electrolyte concentrations were determined to be 0.4 M HCl and 6.3 × 10−5 M Cu(II). The optimal parameters for voltammetric stripping measurements are as follows: an accumulation potential of −0.7 V; an accumulation time of 120 s; and a pulse amplitude and pulse time of 120 mV and 2 ms, respectively. The effect of surface active substances and humic substances as potential interferents present in aqueous environmental samples was investigated. The validation of the procedure was carried out using certified reference materials, like waste water SPS-WW1 and environmental matrix TM-25.5. In addition, the developed procedure was applied to investigate lead recovery from natural environmental water, such as rivers and lakes.

A simple and low-cost differential pulse-adsorptive cathodic stripping voltammetry (DP CSV) approach has been established for trace determination and speciation of Pb using Thorin-I as selective chelating agent. The established assay was based upon controlled preconcentration of Pb–Thorin complex at pH 8.3–9.0 at a hanging mercury dropping electrode (HMDE). The resulting cathodic peak current (Ip,c) at − 0.56 V was then measured versus Ag/AgCl reference electrode. The plot of Ip,c versus Pb concentration under the optimized parameters was linear in the concentration range 3.5 × 10–10 − 5.0 × 10–7 mol L−1. The lower limits of detection (LOD) and quantification (LOQ) of Pb were 1.05 × 10–10 and 3.5 × 10–10 mol L−1, respectively. The planned assay was satisfactorily applied for total analysis and speciation of Pb in various water and food samples. Validation of the developed probe was successfully achieved by analysis of Pb in certified reference material. [ABSTRACT FROM AUTHOR]

The process of electrooxidation of a lead-rhodium binary deposit on a graphite electrode has been studied. The anodic voltammetric curves show the peak of electrooxidation of lead (− 0.52 V), the peak of electrooxidation of hydrogen sorbed on the rhodium (+ 0.2 V), and additional peaks at potentials − 0.42 and − 0.30 V, the nature of which has been investigated. Using the theory of regular solutions, the changes in the equilibrium potentials of lead in lead-rhodium alloys in comparison with the equilibrium potential of lead were calculated. The data obtained showed that the anodic peak at potential − 0.42 V can be due to the selective electrooxidation of lead from the Pb4Rh intermetallic compound (IMC), and the peak at potential − 0.30 V can be due to the selective electrooxidation of lead from the Pb2Rh IMC. The presence of a stable phase structure is confirmed by data obtained by examining the surface of a graphite electrode with a binary lead-rhodium deposit using scanning electron microscopy (SEM). For analytical purposes, it is convenient to use the peak of selective lead electrooxidation from the intermetallic Pb2Rh compound observed on the voltammetric curve at potential − 0.30 V. The current of this peak is proportional to the concentration of rhodium(III) ions in the solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Screen-printed electrodes (SPE) were modified with ligands-containing modifiers. • Inspect factors affecting sensor sensitivity from chemical and physical perspectives. • Verification of sensor sensitivity by detecting trace levels of lead and cadmium. • Computational atomic binding analysis to explain heavy metal–ligand interactions. • Synergy of functional ligands and charged surface electrode enhances SPE sensitivity. The sensitivity of screen-printed electrochemical (SPE) sensors is heavily dependent on the selection of appropriate modifiers that can optimize the chemical (functional ligands, surface charge, binding energy) and physical (morphological structure) properties of the sensor surface. This study aimed to investigate the impact of these chemical and physical factors on the sensitivity of modified SPEs for the detection of lead and cadmium. The study employed anodic stripping voltammetry to evaluate the sensing performance of SPEs modified with different modifiers, including cellulose acetate, chitosan, Nafion, nylon-6, and silver nanoparticles. Results showed that metal-attracting functional groups and surface charged electrode were the dominant factors affecting the sensitivity of SPEs in heavy metal sensing. Specifically, negatively charged electrode surfaces and metal-attracting -SO 3 2- ligands, as found in Nafion-modified SPE, were identified as the key factors in improving sensor selectivity, rather than the rough physical morphology of the SPE, which was believed to provide more metal detection sites. This conclusion was supported by the combination analyses of electrochemical impedance spectroscopy, electrochemically active surface area and computational molecular binding energy of bare and modified SPEs. The findings of this study provide valuable insights for selecting appropriate SPE modifiers and designing sensor architectures for heavy metal detection. [ABSTRACT FROM AUTHOR]

Carbon rod electrodes (CREs) were obtained from recycled zinc⁻carbon batteries and were used without further modification for the measurement of trace concentrations of lead (Pb). The electrochemical behavior of Pb at these electrodes in a variety of supporting electrolytes was investigated by cyclic voltammetry. The anodic peaks obtained on the reverse scans were indicative of Pb being deposited as a thin layer on the electrode surface. The greatest signal⁻to⁻noise ratios were obtained in organic acids compared to mineral acids, and acetic acid was selected as the supporting electrolyte for further studies. Conditions were optimized, and it was possible to determine trace concentrations of Pb by differential pulse anodic stripping voltammetry. A supporting electrolyte of 4% v/v acetic acid, with a deposition potential of −1.5 V (vs. SCE) and a deposition time of 1100 s, was found to be optimum. A linear range of 2.8 µg/L to 110 µg/L was obtained, with an associated detection limit (3σ) of 2.8 µg/L. A mean recovery of 95.6% (CV=3.9%) was obtained for a tap water sample fortified with 21.3 µg/L.

Calixarene bulk modified screen-printed electrodes (SPCCEs) have been designed, fabricated and utilized as one-shot disposable electrochemical sensors towards the simultaneous measurement of toxic metal ions lead(II), copper(II) and mercury(II) within environmental samples. These SPCCEs have been fabricated upon polyester strips, which have been modified over a range of different calixarene compositions. These bespoke sensors have been utilized as disposable electrochemical sensors and quantified in model aqueous solution of 0.1 M HCl giving rise to the simultaneous sensing of lead(II), copper(II) and mercury(II) using cyclic voltammetry and differential pulse anodic stripping voltammetry techniques. These SPCCEs have additionally been applied for the sensing of lead(II), copper(II) and mercury(II) within industrial and environmental samples such as industrial effluents and wastewater samples, furthermore the presented method has been subjected to a comprehensive interference study and further validated with an atomic absorption spectrometric method. [ABSTRACT FROM AUTHOR]

A cost-effective and environmentally friendly method was developed for the simultaneous determination of trace cadmium and lead contaminants in unpolished rice. An ultrasound-assisted digestion (UAD) procedure was ultilized for sample preparation prior to determination of Cd(II) and Pb(II) by anodic stripping voltammetry (ASV) using an eco-friendly bismuth film electrode (BiFE). The efficiency of the proposed UAD procedure was evaluated by certified reference material of glutinous rice powder. The parameters influencing UAD such as solvent system, sample mass, presonication time and sonication time were evaluated. Using the deposition time of 300 s for ASV, linear calibration graphs in a range of 10–200 μg L −1 for Cd(II) and 5–200 μg L −1 Pb(II) were obtained with detection limits of 0.11 and 0.06 μg L −1 for Cd(II) and Pb(II), respectively. Relative standard deviations were 3.5 and 2.3% for 10 μg L −1 of Cd(II) and Pb(II), respectively. The developed system was successfully applied to the analysis of Cd(II) and Pb(II) in various types of organic unpolished rice samples and validated by flame atomic absorption spectrometric method. All studied Thai organic unpolished rice samples were not contaminated with Cd(II) and Pb(II). [ABSTRACT FROM AUTHOR]

Herein, the micro extraction and quantification of lead (II) ions were investigated in trace levels on in situ pulse anodic stripping voltammetry (DPASV) and polytetrafluorethylene (PTFE) membrane-based liquid three-phase micro extraction. The voltammetric cell contained the acceptor solution and reference, the counter, and working electrodes. The modified Pt electrode with 3-Trimethoxysilyl-1-propanethiol and gold nanoparticles (Au NPs), respectively, was applied as the working electrode. The voltammetric cell combined with DPASV was utilized in situ during the extraction time. The obtained results showed the effect of different factors on the pre-concentration and micro extraction of lead ions, including the organic solvent, pH of the donor and acceptor phases, concentration of the complexion agent, extraction time, stirring rate, and electrochemical factors; also, the optimal extraction conditions were established. The final stable signal was achieved after 18-min extraction time for analytical applications. The relative standard deviation and the enrichment factor were obtained to be 6.0% ( $n=5$ ) and 18, respectively. The calibration curve was obtained in the range of 0.207–62.1 ppb Pb(II) (analytical equation: $y=$ 3.986 $x+$ 0.381), and the limit of detection was found to be 0.021 ppb with optimum conditions. The lead (II) ions were determined in fish, rice, and wastewater samples. [ABSTRACT FROM PUBLISHER]

The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7×0.7 cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48 cm; 0.18 cm 2 ). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5 cm×7.5 cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi 3+ (in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively). [ABSTRACT FROM AUTHOR]

Hexaammineruthenium (III) [Ru(NH3)6]3+-Nafion®-isopropanol diluted films were spin coated on indium tin oxide (ITO)-coated glass substrates. The fabricated samples were used to determine the presence of lead and cadmium in solution using anodic stripping voltammetry (ASV). The calibration sensitivity of the electrodes for lead and cadmium were approximately equal. Detection limits of 5ppb and 4ppb were determined for lead and cadmium respectively. Real sampling tests with commercially available yellow water color yielded 0.7106 ppm of Pb with ASV. The result was verified with atomic absorption spectrometry (AAS) which yielded 0.6923ppm of Pb. [ABSTRACT FROM AUTHOR]

Electrochemical sensors based on PET track-etched membranes (TeMs) were prepared by photograft polymerization of 2-hydroxyethylmethacrylate (HEMA) and subsequent formation of interpolyelectrolyte complexes with poly(allylamine) (PAlAm). The functionalized TeMs were characterized by scanning electron microscopy (SEM), FTIR spectroscopy, gas permeability and colorimetric assay. Parameters of graft polymerization such as monomer concentration, time of irradiation, solvent and others were estimated and optimized. Cd(II) and Pb(II) ions were detected by using square wave anodic stripping voltammetry (SW-ASV). Additional modification of the modified membranes with 4-mercaptophenylboronic acid (MPBA) led to increasing of stability of the sensors. The linear range for the detection of Cd(II) and Pb(II) ions using the modified electrode was 50 µg - 4.25 mg/L and 10 µg – 4.25 mg/L. Moreover, the obtained results of SW-ASV demonstrated that the enhancement in the electrochemical signals was achieved with PET TeMs-g-PHEMA-PAlAm\MPBA compared to that of a bare PET TeMs-g-PHEMA. Selectivity test showed that alkali and alkaline earth metal ions, except for magnesium (up to 1 mg/l), do not particularly interfere with the determination of lead and cadmium in the analyte. Sensing of Pb and Cd ions in river water demonstrate us that prepared sensors can be used in real conditions with sufficient accuracy and reproducibility of the results. [Display omitted] • The modification of membranes by graft polymerization of 2-HEMA. • Formation of interpolyelectrolyte complexes with PAlAm on the membrane surface. • Modification with MPBA led to increase the stability of sensors. • SW-ASV used to for detection of Pb2+ and Cd2+ ions in water. • Modified membranes with interpolyelectrolyte complexes led to improve LOD. [ABSTRACT FROM AUTHOR]

High-adsorption MnFe 2 O 4 nanocrystal clusters (MnFe 2 O 4 NC) with mesoporous structure were used for selective analysis of Pb 2 + by square wave anodic stripping voltammetry (SWASV) in this work. The as-prepared MnFe 2 O 4 NCs with diameter of 200–400 nm and mesoporous structure composed of nanocrystals with a size of about 8–12 nm were characterized using SEM, HRTEM and XRD. Electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The chemical and electrochemical parameters influencing on deposition and stripping of metal ions, such as supporting electrolytes, pH value, deposition potential, and deposition time, were also studied. The MnFe 2 O 4 NC modified GCE has a high selectivity toward Pb 2 + with a favorable sensitivity (19.9 μA μM − 1 ) and LOD (0.054 μM) for Pb 2 + under the optimized conditions while the response to Cd 2 + , Hg 2 + , Cu 2 + and Zn 2 + is poor. No interference from Cd 2 + , Zn 2 + and Hg 2 + , favorable stability and potential practical applicability were recognized in the electrochemical determination of Pb 2 + . The above results provided a potential material for the design of new sensing materials in the application field of electrochemical detection toward toxic metal ions. [ABSTRACT FROM AUTHOR]

The performance of glassy carbon electrodes (GCE) coated with multi-walled carbon nanotube poly(pyrocatechol violet) composite and bismuth film was investigated as an electrochemical sensor in the simultaneous determination of Cd 2+ and Pb 2+ ions in a 0.1 M acetate buffer solution at pH = 5.0. The presence of the bismuth film improves the analyte accumulation due to its ability to form a fused alloy with cadmium and lead. It was found that the Bi-film modified electrode shows a better performance than the bare GCE, GCE-MWCNT and GCE-MWCNT/poly(PCV) electrodes. The parameters affecting the stripping current response were investigated and optimized. Under optimal conditions, the electrode showed a good linear response to Cd 2+ and Pb 2+ in the concentration range of 1.0–300.0 μg L −1 and 1.0–200.0 μg L −1 , respectively. The detection limits were 0.20 μg L −1 and 0.40 μg L −1 for Cd 2+ and Pb 2+ , respectively. It was found that the sensor has least interference from most of the common ions due to specific and selective interaction of the modifier functionalities with lead and cadmium ions. The response of the electrode remained constant for at least 3 weeks of successive operation. The proposed method was applied for simultaneous determining Cd 2+ and Pb 2+ contents in water samples. [ABSTRACT FROM AUTHOR]

The fabrication and evaluation of a glassy carbon electrode (GCE) modified with ordered mesoporous carbon (OMC), 2-mercaptoethanesulfonate (MES)-tethered polyaniline (PANI) and bismuth for simultaneous determination of trace Cd2+ and Pb2+ by differential pulse anodic stripping voltammetry (DPASV) are presented here. The morphology and electrochemical properties of the fabricated electrode were respectively characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Experimental parameters such as PANI disposition, preconcentration potential, preconcentration time and bismuth concentration were optimized. Under optimum conditions, the fabricated electrode exhibited linear calibration curves ranged from 1 to 120 nM for Cd2+ and Pb2+. The limits of detection ( LOD) were 0.26 nM for Cd2+ and 0.16 nM for Pb2+ ( S/ N=3), respectively. Additionally, repeatability, reproducibility, interference and application were also investigated, and the proposed electrode exhibited excellent performance. The proposed method could be extended for the development of other new sensors for heavy metal determination. [ABSTRACT FROM AUTHOR]

Single-walled bismuth nanotubes (sw-BiNTs) were self-assembled with octa(3-aminopropyl) silsesquioxane as a framework and to govern morphology. Deposited on a glassy carbon electrode (GCE), the sw-BiNTs were used for the simultaneous analysis of Pb(II) and Cd(II) by square wave stripping voltammetry. The sw-BiNTs were prepared by (a) coordination interaction between the amino groups of the silsesquioxane and the Bi(III) ions, and by (b) reduction with sodium borohydride. Transmission electron microscopy images revealed single-walled tubular structures with diameters of ~4-6 nm, and with lengths of several hundreds nanometers. GCEs modified with such sw-BiNTs perform much better than bare GCEs in stripping analysis of Pb(II) and Cd(II). The effects of adsorption quantity of sw-BiNTs, solution pH, pulse amplitude, and pulse width were optimized. The modified electrode was then used for the analysis of Pb(II) and Cd(II) in a linear response range from 0.4 to 6 μM with a sensitivity of 4.692 μA μM and 3.835 μA μM, and detection limits of 1 nM and 5 nM, respectively. The method was successfully applied to the analysis of Pb(II) and Cd(II) in toy leachates, and the results were in good agreement with those obtained with atomic absorption spectrometry. Sensitivity and detection limits were compared with other voltammetric methods, and the sw-BiNTs are deemed to be an attractive alternative for practical applications. Other features of the electrode include low costs, a well reproducible nanostructure, and ease of scale-up of the fabrication process. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The paper describes the results of stripping voltammetry usage to control concentration of lead ion which are formed during electrochemical detoxication of organic pollutants. Optimal conditions for the analysis of Pb 2+ were selected, i.e. 0.05 N KOH is an electrolyte, the deposition potential (-0.55) V, deposition time of 4 minutes, the amount of analyzed sample was 0.1 ml. The presence of organic matter does not affect the quantitative determination of lead ions. The developed method allows us to estimate the concentration of Pb 2+ in the amount of electrolyte at disposal of toxicants quickly and with a high degree of sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Recently, our research group has developed a novel carbon paste composite electrode, in which titanium dioxide/zirconium dioxide was incorporated into graphite carbon paste, to detect cadmium and lead in aqueous solution via cyclic voltammetry. In the current work, the newly developed titanium dioxide/zirconium dioxide carbon paste composite electrode was used to quantify lead and cadmium, individually and simultaneously, utilizing square wave anodic stripping voltammetry. In addition to optimization of multiple stripping analysis parameters, trace levels quantification of both metals was attempted. Using the mentioned titanium dioxide/zirconium dioxide carbon paste composite electrode, the detection limits, in modeling solutions, for Pb and Cd were estimated to be 0.48ppb and 0.77ppb, respectively. Furthermore, reproducibility of analytical stripping current signal was also calculated and expressed as relative standard deviation for both metals, 3.8% for Cd and 2.5% for Pb (n =10). The proposed sensor was also tested in river water and well water samples to illustrate its potential for real world application. Moreover, scanning electron microscopy was employed to investigate and characterize the electrode surface morphology. [Copyright &y& Elsevier]

In the present work, a sensitive, facile and disposable sensing platform for trace analysis of heavy metal ions was developed at the Bi modified graphene-poly(sodium 4-styrenesulfonate) composite film screen printed electrode (GR/PSS/Bi/SPE). The GR/PSS/Bi/SPE improved sensitivity and linearity due to the functionalization of graphene with negatively charged PSS providing more absorbing sites. The detection limit of the GR/PSS/Bi/SPE is found to be 0.042 µg L−1 for Cd2+ and 0.089 µg L−1 for Pb2+ with linear responses of Cd2+ and Pb2+ in the range of 0.5-120 µg L−1. Finally, the practical application was confirmed in real water with satisfactory results. [ABSTRACT FROM AUTHOR]

Mercury-based screen-printed electrodes (SPE) combined with square-wave anodic stripping voltammetry (SWASV) techniques for the analysis of copper, cadmium, lead, and zinc in different water samples have been applied. The detection system has been implemented in a flow cell and different experimental conditions have been tested in view of its application forin-situmonitoring. In particular, an acetate buffer together with a low chloride concentration (0.025 M NaCl) provided best performance and reproducible results. Additionally, the flow system was validated for the first time in terms of limits of detection, linearity, repeatability and recovery. Limits of detection of 2.8 µg L−1, 4.1 µg L−1, and 7.5 µg L−1for cadmium, lead and copper respectively and repeatabilities lower than 10% (as RSD) were found. Good recoveries have been obtained for the three cations and in particular for copper, even in the presence of zinc. Finally, the method has shown its efficiency for the rapid screening of lead, cadmium and copper contained in both natural waters and wastewater samples. [ABSTRACT FROM AUTHOR]

This work presents a disposable bismuth-antimony film electrode fabricated on screen-printed electrode (SPE) substrates for lead(II) determination. This bismuth-antimony film screen-printed electrode (Bi-SbSPE) is simply prepared by simultaneously in situ depositing bismuth(III) and antimony(III) with analytes on the homemade SPE. The Bi-SbSPE can provide an enhanced electrochemical stripping signal for lead(II) compared to bismuth film screen-printed electrodes (BiSPE), antimony film screen-printed electrodes (SbSPE) and bismuth-antimony film glassy carbon electrodes (Bi-SbGC). Under optimized conditions, the Bi-SbSPE exhibits attractive linear responses towards lead(II) with a detection limit of 0.07 µg/L. The Bi-SbSPE has been demonstrated successfully to detect lead in river water sample. [ABSTRACT FROM AUTHOR]

A novel strategy for the automation of trace lead (Pb) and cadmium (Cd) anodic stripping voltammetry (ASV) is described. This was achieved using an electrode assembly comprising a small standard reference electrode, a Pt wire counter electrode, and an in situ bismuth-plated pencil lead working electrode for ASV in a robotic device adapted for measurements in a 24-well microtiter plate format. The movement of the electrode assembly through individual wells was by computer-controlled micropositioning, and each microtiter plate run included a sequence of electrode pretreatment, water rinsing, and simultaneous Pb and Cd ASV measurements. Analyte concentrations down to 2 μg/L (Pb) and 20 μg/L (Cd) could be measured in drinking and tap water, a wastewater reference material and a soil sample, with an accuracy and standard deviation typical of stripping analysis. This robotic electrochemical strategy offers automated trace metal analysis with simple instrumentation and is suggested as an option for routine use in analytical laboratories such as those providing environmental heavy metal testing services. [ABSTRACT FROM AUTHOR]

Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO), in 1 mol/L HCl at −1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead ( n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead. [ABSTRACT FROM AUTHOR]

Blood samples of 160 children, ranging age between 3 months and 6 years were selected from five different parts of Amritsar district of Punjab (India) and were analyzed for Zn, Cd, Pb and Cu using anodic stripping voltammetry. Large variations in the results have been correlated to the area inhabited, age differences and other factors. It was found that the areas, more prone to environmental stress, had shown more quantities of these metals in blood samples in comparison to those which were taken from safer sites. Similarly the younger children lesser exposed to environmental pollution had shown comparatively lesser quantity of these metals in comparison to older objects.

A new type of covalent bulk modified glassy carbon composite electrode has been fabricated and utilized in the simultaneous determination of lead and cadmium ions in aqueous medium. The covalent bulk modification was achieved by the chemical reduction of 2-hydroxybenzoic acid diazonium tetrafluroborate in the presence of hypophosphorous acid as a chemical reducing agent. The covalent attachment of the modifier molecule was examined by studying Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and the surface morphology was examined by scanning electron microscopy images. The electrochemistry of modified glassy carbon spheres was studied by its cyclic voltammetry to decipher the complexing ability of the modifier molecules towards Pb and Cd ions. The developed sensor showed a linear response in the concentration range 1-10 μM with a detection limit of 0.18 and 0.20 μM for lead and cadmium, respectively. The applicability of the proposed sensor has been checked by measuring the lead and cadmium levels quantitatively from sewage water and battery effluent samples. [ABSTRACT FROM AUTHOR]

The present study serves to focus attention on the modification of multiwalled carbon nanotube with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and its application for the development of a new, simple, and selective modified electrode in order to determine Pb(II) in standard alloys and water samples. The electrochemical method was based on open circuit accumulation of lead ions onto a 5-Br-PADAP-modified multiwalled carbon nanotube electrode and then their anodic stripping voltammetric determination. The linear range for Pb(II) ions was from 0.9 to 114.6 μg L. The detection limit and relative standard deviation were found to be 0.1 μg L and 1.6%, respectively. This method demonstrates the powerful application of carbon nanotubes in the field of mercury-free electrodes in voltammetric stripping analysis. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasensitive electrochemical method for simultaneous determination of lead and cadmium was first developed using the novel bismuth–Nafion-medical stone doped disposable electrode (an improved wax-impregnated graphite electrode). Through the synergistic sensitization effect of the resulting composite material, the disposable electrode showed remarkable electrochemical responses to lead and cadmium. The oxidation of the two metals produced two well-defined and separated square wave peaks at about −0.62V for Pb2+ and −0.85V for Cd2+, respectively. The effects of the amount of medical stone, concentration of Nafion, thickness of bismuth, pH of buffer solution, deposition potential, accumulation time, voltammetric measurement and possible interferences were investigated in detail. Under the optimal conditions, the fabricated electrode exhibited linear ranges from 2.0 to 12.0μgL−1 with detection limit of 0.07μgL−1 for lead and 2.0–12.0μgL−1 with detection limit of 0.47μgL−1 for cadmium. The assay results of heavy metals in wastewater with the proposed method were in acceptable agreement with the atomic absorption spectroscopy method. [Copyright &y& Elsevier]

A square-wave anodic-stripping voltammetric method for the analysis of lead and cadmium in chicken muscle and liver was developed and validated, and the results of a monitoring study relative to chicken and pigeon meat are reported. The voltammetric method allows the analysis of lead and cadmium at the same time in samples after acid digestion. The use of perchloric acid for digestion and of acetate buffer in the supporting electrolyte are suitable to reduce matrix interferences and obtain limits of quantification which were below 10 ng g−1 for meat and liver samples. The regression between the analytical signal and the concentration of the target analytes in spiked samples and Certified Reference Materials proved to be linear within the 10–100 ng g−1 range for meat and within the 50–500 ng g−1 range for liver. The analytical method was verified using available Certified Reference Materials BCR-184 (cattle meat) and BCR-185R (cattle liver) as well as with spiked chicken samples. Precision (i.e. repeatability and intermediate precision) and accuracy (percentage recovery and bias) were of the order of 0.3–4.5% for both lead and cadmium The level of lead in muscle was in the range between 6.4 and 59.8 ng g−1 in chickens and between 7.9 and 63.6 ng g−1 in farmed pigeons, whereas it was between 8.0 and 84.4 ng g−1 in chicken liver. The cadmium concentration was 0.4–10.4 ng g−1 in chicken muscle, 10.4–90.6 ng g−1 in chicken liver and 2.2–8.0 ng g−1 in farmed pigeons. [ABSTRACT FROM AUTHOR]

Abstract: A bismuth-film modified graphite nanofibers–Nafion glassy carbon electrode (BiF/GNFs–NA/GCE) was constructed for the simultaneous determination of trace Cd(II) and Pb(II). The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as deposition potential, deposition time, and bismuth ion concentration were optimized for the purpose of determination of trace metal ions in 0.10M acetate buffer solution (pH 4.5). Under optimal conditions, based on three times the standard deviation of the baseline, the limits of detection were 0.09μgL−1 for Cd(II) and 0.02μgL−1 for Pb(II) with a 10min preconcentration. In addition, the BiF/GNFs–NA/GCE displayed good reproducibility and selectivity, making it suitable for the simultaneous determination of Cd(II) and Pb(II) in real sample such as river water and human blood samples. [ABSTRACT FROM AUTHOR]

Abstract: This review describes the use of electrochemical sensors for lead detection, focusing on sensors modified with bismuth (Bi) that are more “environment friendly” than mercury electrodes. We report and discuss the experimental variables that affect lead measurement using Bi-modified electrodes. We highlight the practical problems of lead contamination encountered during sample treatment and lead detection, in order to give a valid, rounded picture. In addition, we report and discuss different treatments needed for lead detection in natural samples (food, clinical and environmental) using Bi sensors. [Copyright &y& Elsevier]

Abstract: This work describes a novel type of renovated silver ring electrode (RSRE), as mercury-free sensor, for anodic stripping voltammetry (ASV). The great advantages of the RSRE are simplicity, periodic renovation of the surface and the possibility of repetitive measurements on the surface completely free from reaction products, adsorbed surface-active species, etc. The sensor was tested for the detection of nanomolar concentrations of Pb2+ and Cd2+ by ASV in water samples without removal of oxygen and surfactants. Detection limits of 0.5nM for Pb2+ and 2nM for Cd2+ have been achieved following 60s electrodeposition. The validation of the proposed RSRE was made by Pb2+ and Cd2+ determination using the certified reference materials (Surface Waters). The RSRE was successfully applied to Pb2+ and Cd2+ analysis in tap water and to river water with a high content of organic contaminants. [Copyright &y& Elsevier]