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The detection of trace heavy metal ions is important in monitoring water quality, a vital freshwater source. This study presents the preparation of a multi-walled carbon nanotube (MWCNTs) paste electrode using a pasting mixture of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid ([Bmim][PF6] IL) and paraffin oil for the determination of Cd2+ and Pb2+. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy were applied to characterize the paste composites. The electrochemical behavior of the fabricated electrodes was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The [Bmim][PF6]-MWCNTs electrode showed enhanced sensitivity for Cd2+ and Pb2+ detections over linear sweep anodic stripping voltammetry (LSASV) performances. Experimental results showed that the MWCNTs-IL-1 electrode using a pasting mixture of 10 μL of [Bmim][PF6] and 190 μL of paraffin oil was the most suitable for Cd2+ and Pb2+ determinations. The LSASV conditions for Cd2+ and Pb2+ analysis at the MWCNTs-IL-1 electrode were optimized, including the deposition potential, deposition time, and pH of the working solution. The stripping peak currents were linearly correlated with the concentration ranges of Cd2+ (1–35 μg/L) and Pb2+ (1–90 μg/L) for both individual and simultaneous determinations. The MWCNTs-IL-1 electrode exhibited high repeatability, reproducibility, and stability over a 30-day storage period. The real applicability of the MWCNTs-IL-1 electrode was demonstrated by successful determinations of Cd2+ and Pb2+ concentrations in tap water and surface water samples, which agreed with the results obtained by inductively coupled plasma mass spectrometry. [ABSTRACT FROM AUTHOR]

Seafood consumption is the primary exposure route for trace metals like mercury. Accordingly, canned tuna meat has been focused on by researchers because of the potential bioaccumulation of high amounts of mercury. This study aimed to test a novel and reliable electroanalytical method employing a working electrode consisting of gold-nanoparticle-modified carbon microfibers to quantify total mercury in canned tuna samples. Determination was achieved via differential pulse anodic stripping voltammetry. The proposed method had a limit of detection of 3.9781 ± 0.0001 μg L−1 and a limit of quantification of 33.6634 ± 0.0001 μg L−1, with a sensitivity of 0.3275 nA μg L−1. The modified electrode was evaluated in samples taken from three canned tuna brands sold in the Sangolquí parish in Rumiñahui, Ecuador. These brands, coded A, B, and C, represent 47.92%, 27.08%, and 11.98% of all canned tuna sold in the Ecuadorian market, respectively. The resulting respective total mercury concentrations were 0.5999 ± 0.0001 mg kg−1; 0.9387 ± 0.0001 mg kg−1; and 0.3442 ± 0.0001 mg kg−1 for A, B, and C. Method accuracy was determined through the recovery percentages of ≥98%, which indicated acceptable accuracy for the final optimized method. Mean mercury concentrations for all samples did not represent a carcinogenic risk for consumers. However, the values obtained for potential no-carcinogenic risk and daily consumption rate suggest that consumers of tuna canned in water, particularly brand C, may be at risk. [Display omitted] • Electrochemically quantifying Hg in canned tuna meat is novel, reliable, simple. • LD/LQ below allowed Hg concentration: 3.9781 ± 0.0001 μg L−1 and 33.6634 ± 0.0001 μg L−1 • Total Hg complied with Ecuadorian INEN's Regulation 184 (less than 1 mg kg−1). • Total Hg obtained was not a carcinogenic risk. • But potential noncarcinogenic risk/daily consumption rate could endanger consumers. [ABSTRACT FROM AUTHOR]

Diabetes is a chronic disease characterized by elevated blood glucose levels resulting from absent or ineffective insulin release from pancreatic β-cells. β-cell function is routinely assessed in vitro using static or dynamic glucose-stimulated insulin secretion (GSIS) assays followed by insulin quantification via time-consuming, costly enzyme-linked immunosorbent assays (ELISA). In this study, we developed a highly sensitive electrochemical sensor for zinc (Zn2+), an ion co-released with insulin, as a rapid and low-cost method for measuring dynamic insulin release. Different modifications to glassy carbon electrodes (GCE) were evaluated to develop a sensor that detects physiological Zn2+ concentrations while operating within a biological Krebs Ringer Buffer (KRB) medium (pH 7.2). Electrodeposition of bismuth and indium improved Zn2+ sensitivity and limit of detection (LOD), and a Nafion coating improved selectivity. Using anodic stripping voltammetry (ASV) with a pre-concentration time of 6 min, we achieved a LOD of 2.3 μg/L over the wide linear range of 2.5–500 μg/L Zn2+. Sensor performance improved with 10-min pre-concentration, resulting in increased sensitivity, lower LOD (0.18 μg/L), and a bilinear response over the range of 0.25–10 μg/L Zn2+. We further characterized the physicochemical properties of the Zn2+ sensor using scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Finally, we demonstrated the sensor's capability to measure Zn2+ release from glucose-stimulated INS-1 β-cells and primary mouse islets. Our results exhibited a high correlation with secreted insulin and validated the sensor's potential as a rapid alternative to conventional two-step GSIS plus ELISA methods. [ABSTRACT FROM AUTHOR]

The concentrations of lead, copper and cadmium in soil and plant samples collected from Abare and Dareta villages in Anka local government area of Zamfara State, Nigeria have been electrochemically determined. The study was carried out because of the high mortality of women and children under five, reported for these areas in June 2010. The cause was ascribed to the lead poisoning which has been related to the mining and processing of gold-containing ores. Linear sweep anodic stripping voltammetry technique was used with the glassy carbon working, Ag/AgCl reference and platinum auxiliary electrodes. Voltammetric peaks for lead, copper and cadmium that were observed at -495 mV, -19.4 mV and -675 mV, respectively, have formed a basis for construction of the corresponding calibration plots. The concentrations (in mg/kg) of lead, copper and cadmium in the soil samples were found in the ranges of 18.99−26087.70, 2.96−584.60 and 0.00−1354.25, respectively. The concentration values for lead were far above already established USEPA (2002) and WHO (1996) maximum permissible limits for residential areas. The concentrations of lead, copper and cadmium in the food samples ranged between 5.70−79.91, 11.17−41.21 and 0.00−5.74 mg/kg. Several of these values are found well above the FAO/WHO limits of 0.1, 2 and 0.1 mg/kg, respectively. The results indicate that in addition to the lead poisoning, copper and cadmium poisoning may also be responsible for sudden and high mortality in this population.

Pre-concentration and determination of Zn (II) across a ligand assisted pseudo stirbar hollow fiber solid/liquid phase microextraction method in water samples has been investigated. All detections were carried out by differential pulse anodic stripping voltammetry (DPASV). The method involves microextraction and pre-concentration of Zn (II) on the pseudo stir bar hollow fiber. Then desorption has been done using suitable solvent containing suitable ligand as complexing agent. The optimized conditions were obtained. The relationship between the peak current and concentration was linear over the range of 0.05–500 ng mL−1. The limit of detection was 0.015 ng mL−1. Under the optimized conditions, the pre-concentration factor is 5140. The applicability of the developed technique was evaluated by application to spiked, environmental water samples.

Electrochemical detection systems are very promising for pollution monitoring owing to their easy miniaturization and low cost. For this purpose, we have recently developed a new concept of device based on Electrodes Array for Sampled-Current Voltammetry (EASCV), which is compatible with miniaturization and portability. In this work, to improve the sensitivity of the analytical method, we added a preconcentration step before EASCV analysis, combining sampled-current voltammetry with anodic stripping voltammetry. Lead was chosen as analyte for this probe of concept owing to its high toxicity. The conditions for electrodeposition of lead on gold were optimized by means of under potential deposition. Current intensities 300 times higher than with linear sweep anodic stripping voltammetry were obtained, showing the interest in the method. The value of the sampling time directly affected the sensitivity of the sensor given by the slope of the linear calibration curve. The sensor exhibited a limit of detection of 1.16 mg L−1, similar to those obtained with linear sweep anodic stripping voltammetry.

It is of prime importance to determine the presence of trace heavy metals, especially cadmium (Cd2 ^+ ) and lead (Pb2 ^+ ) in rice to ensure food safety as it is the staple source of the daily caloric intake of Asians. This work utilized anodic stripping voltammetry (ASV) for the determination of heavy metals due to its portability for in situ measurements. A glassy electrode modified with silver nanoparticles (AgNP), bismuth nanoparticles (BiNP), multiwalled carbon nanotubes (MWCNT) and Nafion was fabricated to serve as the working electrode. The morphology of the fabricated electrode was characterized using scanning electron microscopy and x-ray diffraction, its elemental composition was determined by energy dispersive spectroscopy, its chemical bonds were identified using Fourier transform infrared spectroscopy, and its electrochemical behavior was measured via cyclic voltammetry. The electrode showed high stability at 50 continuous scans. The optimal deposition time, accumulation time and scan rate were determined to be 80 s, 60 s and 100 mV s−1, respectively. The detection limit for Cd2 ^+ and Pb2 ^+ were determined to be 25.12 ppb and 20.55 ppb, respectively. Rice samples were analyzed and the transfer factor of the heavy metals were determined at each isolated part. The ASV results were validated with atomic absorption spectroscopy.

In this work, bismuth films were electrodeposited in situ onto carbon paste electrodes (CPEs) and they were used for lead determination in tap water samples by anodic stripping square wave voltammetry. The analytical performance of CPEs prepared with different binder agents was compared. It was observed that CPEs prepared with solid paraffin as binder agent provided the best results. All parameters of the analytical method were optimized and the best conditions obtained were: acetate buffer 0.1 mol L-1 (pH=4.75) as supporting electrolyte; pre-concentration time of 240 s and electrodepositing potential of -1.2 V vs. Ag/AgCl/KClsat. The best Bi3+ concentration was 2.0 μmol L-1. At these optimized conditions, analytical curves were constructed and two linear regions were obtained: 25 to 100 nmol L-1 and 250 to 1000 nmol L-1. Detection limits (LD) corresponding to these linear ranges were, respectively, 5.77 and 52.3 nmol L-1. Recovery experiments were performed in tap water samples and recovery percentages close to 100 % were always obtained although the best results were obtained for samples spiked with 250 nmol L-1 of Pb2+.

A simple procedure for field fish sample pretreatment was developed. This treatment in combination with square wave anodic stripping voltammetry (SW-ASV) with solid gold electrodes (SGE) and gold nanoparticle-modified glassy carbon electrodes (AuNPs-GCE) was applied for the determination of total mercury content. A certified reference material (CRM, Tuna Fish BCR 463), ten freeze-dried samples of canned tuna and two fresh fish samples were analysed both with a bench-top voltammetric analyser after microwave digestion and with a portable potentiostat after mild eating using a small commercial food warmer. The results obtained by the two SW-ASV approaches and by a Direct Mercury Analyser (DMA), the official method for mercury determination, were in very good agreement. In particular, (i) the results obtained with in field procedure are consistent with those obtained with the conventional microwave digestion; (ii) the presence of gold nanoparticles on the active electrode surface permits an improvement of the analytical performance in comparison to the SGE: the Limit of Quantification (LOQ) for mercury in fish-matrix was 0.1 μg L−1 (Hg cell concentration), corresponding to 0.06 mg kg−1 wet fish, which is a performance comparable to that of DMA. The pretreatment proposed in this study is very easy and applicable to fresh fish; in combination with a portable potentiostat, it proved to be an interesting procedure for on-site mercury determination.

A glassy carbon electrode covered with thiol-functionalized polysiloxane film modified by electrodeposited lead nanoparticles was used for determination of Ag(I) by square-wave anodic stripping voltammetry. The sol-gel methodology based on co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of cetyltrimethylammonium bromide (CTAB) was applied to synthesize an organosilica sol that was used to modify electrode surface. Silver ions were accumulated on the electrode surface by complexation with thiol groups and then simultaneously deposited with Pb nanoparticles by reduction at − 0.85 V. The Pb nanoparticles used as modifier of polyslioxane film significantly improved the electrochemical performance of the sensor. Under optimized conditions, the voltammetric signal was proportional to the Ag(I) concentration in the range of 0.0093 to 1.85 nmol L − 1 with excellent limits of detection and quantification of 1.2 pmol L − 1 and 4.1 pmol L − 1 after 90 s of accumulation on the electrode surface covered with thiol-functionalized polysiloxane film, respectively. The proposed method was applied for determination of Ag(I) in river water samples collected from Bystrzyca and Vistula without mineralization and a total silver concentration in commercially available silver-containing products. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor was developed for the sensitive and selective detection of Cu 2 + , Pb 2 + and Cd 2 + , which was based on NH 2 -MIL-88(Fe)-rGO composite modified glass carbon electrode (NH 2 -MIL-88(Fe)-rGO/GCE). The NH 2 -MIL-88(Fe)-rGO composite was facilely prepared by a one-step method and characterized by SEM, XRD, Raman spectrum and electrochemical methods. The stepwise GCE modified process was investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of Cu 2 + , Pb 2 + and Cd 2 + ions on the NH 2 -MIL-88(Fe)-rGO/GCE were explored by differential pulse anodic stripping voltammetry (DPASV). It was found that NH 2 -MIL-88(Fe)-rGO was capable of adsorbing Cu 2 + , Pb 2 + and Cd 2 + ions from aqueous solutions and the NH 2 -MIL-88(Fe)-rGO/GCE could enhance the electrochemical responses of Cu 2 + , Pb 2 + and Cd 2 + effectively. Important operational parameters such as electrolyte pH and deposition time were investigated and optimized for the determination of trace Cu 2 + , Pb 2 + and Cd 2 + ions. Under the optimum conditions, the proposed electrochemical sensor had a linear range of 0.005––0.3 μM for Cd 2 + , 0.01–0.3 μM for Pb 2 + and 0.005–0.05 μM for Cu 2 + , respectively. The limits of detection (LODs) are 4.9 nM for Cd 2 + , 10 nM for Pb 2 + and 3.6 nM for Cu 2 + , respectively. The proposed method has been successfully applied to determine three metal ions in water samples. The developed sensor promises simple preparation, fast operation, good sensitivity and excellent reusability, showing great potential for monitoring of water quality. [ABSTRACT FROM AUTHOR]

A nanocomposite of flake-shaped manganese-terephthalic acid MOF/single-walled carbon nanotubes (Mn(TPA)-SWCNTs) was synthesized using manganese chloride, terephthalic acid and SWCNTs as raw materials. Theoretical modeling study shows that the Mn(TPA) component has stronger adsorption ability to lead ion (Pb 2+ ) than the other common heavy metal ions, which is in good agreement with the result of electrochemical assay. Then, the Mn(TPA)-SWCNTs were used as a sensing matrix for the voltammetric determination of Pb 2+ . The results displayed that the sensor shows high analytical performance for Pb 2+ due to the synergy of Mn(TPA) with highly selective binding to Pb 2+ and SWCNTs with high electronic conductivity. Under the optimal conditions, the Mn(TPA)-SWCNTs-based electrochemical sensor presented a wide linear response over the concentration range from 0.10 to 14.0 μM. The limit of detection was achieved to be 38 nM. Satisfactory results were also achieved when the Mn(TPA)-SWCNTs-based sensor was utilized for the determination of Pb 2+ in the practical samples of industrial wastewater and human serum, suggesting great promising of the sensor for practical application. [ABSTRACT FROM AUTHOR]

Anodic stripping voltammetry (ASV) is an analysis technique that permits the selective and quantitative analysis of metal ion species in solution. It is most commonly applied in neutral to acidic electrolyte largely due to inherent metal ion solubility. Bismuth (Bi) is a common film used for ASV due to its good sensitivity, overall stability and insensitivity to O2. ASV, utilizing a Bi film, along with cadmium (Cd) and lead (Pb) as the plating mediators, has recently been adapted to determine zinc (Zn) concentrations in highly alkaline environments (30 % NaOH or 35 % M KOH). Successful analysis of Zn in alkaline relies on the ability of the hydroxide to form soluble metal anion species, such as Bi(OH)4− and Zn(OH)42−. Here, we look to extend this technique to detect and quantify copper (Cu) ions in these highly basic electrolytes. However, in general, the use of ASV to detect and quantify Cu ion concentrations is notoriously difficult as the Cu stripping peak potential overlays with that of Bi from the common Bi film electrode. Here, an ASV method for determining Cu concentration in alkaline solutions is developed utilizing Pb as a deposition mediator. As such, it was found that when analyzing Cu solutions in the presence of Pb, the stripping voltammetry curves present separate and defined Cu stripping peaks. Different analyzes were made to find the best stripping voltammetry performance conditions. As such, an accumulation time of 5 minutes, an accumulation potential of≤−1.45 V vs. Hg/HgO, and a concentration of 35 wt% KOH were determined to be the conditions that presented the best ASV results. Utilizing these conditions, calibration curves in the presence of 5.0 ppm Pb showed the best linear stripping signal correlation with an r-squared value of 0.991 and a limit of detection (LOD) of 0.67 ppm. These results give way to evaluating Cu concentrations using ASV in aqueous alkaline solutions. [ABSTRACT FROM AUTHOR]

A glassy carbon electrode,covered with a Nafion film, on which nano-structured bimetallic particles of Ag-Hg were deposited; from now on “the AgHgNpNf/GC electrode”, was used for the indirect determination of cysteine, glutathione and metallothioneins by measuring the catalytic hydrogen evolution signal according to the Brdička reaction using cobalt as a catalyst. Upon successful formation and deposition of the Ag-Hg bimetallic nanoparticles cyclic voltammetry (CV), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the electrode for that specific task. The results showed the electrode to be mechanically resistant even under sonication, stable in its performance, porous, sensitive in its response and of low cost to be built. Differential pulse voltammetry signals for cysteine and glutathione obtained using the AgHgNpNf/GC electrode were qualitatively similar to those reported using a hanging mercury drop electrode, (HMDE), dropping mercury electrode (DME) and static mercury drop electrode (SMDE). Detection limits based on the variability of a blank solution, (3 s criterion) calculated for those tests were 0.463 μg L −1 and 0.064 μg L −1 , for cysteine and glutathione, respectively. Based on the Brdička procedure and considering the particular characteristics of the new electrode, some analytical tests were carried out for the indirect determination of the metallothioneins content of samples of blood serum of rats exposed to lead by measuring the evolution of the catalytic hydrogen signal. An average accuracy value around 102%, n = 6, and a precision of 0.87% ± 0.09 were obtained for these tests. [ABSTRACT FROM AUTHOR]

With an aim of developing a mercury-free electrode for anodic stripping voltammetric determination of Pb (II) ions, a poly zincon film (PZF) modified electrode is reported here. The PZF on the electrode surface has been obtained by electropolymerisation of zincon. PZF present on the electrode surface has been used for preconcentrating Pb (II) ions through complexation. The electrochemical determination of the above metal ion has been carried out by reducing the preconcentrated Pb (II) at −1.0 V followed by anodic stripping in acetate buffer of pH 6 and measuring the stripping current at −0.64 V. The PZF and Pb preconcentrated PZF modified electrodes have been characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The factors influencing the determination of Pb (II) ions such as the nature of medium/background electrolyte, pH, preconcentration time and electrode regeneration have been studied in detail. Under optimum conditions, a linear relation for the stripping current with Pb (II) ions in the solution has been observed in the range from 3.45 to 136.3 μg L −1 with a detection limit of 0.98 μg L −1 . The regeneration of the modified electrode after each experiment has been achieved by simply immersing the electrode in 0.1 M EDTA solution for 2 min and washing thoroughly in de-ionised water. PZF modified electrode has shown a promising and sensitive platform for the anodic stripping determination of Pb (II) ions and the regeneration of the electrode has been found to be easy for subsequent uses. The proposed method has been applied for the determination of Pb (II) ions in ground water and tap water samples. [ABSTRACT FROM AUTHOR]

Anodic stripping voltammetry (ASV) with rotating glassy carbon electrode (RGCE) and microfiber carbon electrode (μFCE), both filmed with mercury, were used to determine copper content in wine. Influence of phenolics on in situ mercury film formation was studied. Wine and quercetin were added gradually into solution of Hg(II) in acetic acid-sodium acetate buffer (pH = 4.60). Reduction of Hg(II) was observed in both cases. In situ filmed electrode was found unsuitable. Results obtained using ex situ filmed RGCE and μFCE were found in good agreement with ASV using hanging mercury drop electrode. Thus, ASV with ex situ mercury filmed electrodes can be recommended for accurate quantification of copper in complex samples containing phenolics, without any special pretreatments. [ABSTRACT FROM AUTHOR]

An ASV procedure featuring a new tellurium film electrode deposited in-situ on a glassy carbon substrate in 0.1 M HCl is presented. The electrochemical behavior of the tellurium film electrode with regard to its applicability in the ASV determination of copper(II) was thoroughly studied and discussed. It was found that during the accumulation step in 0.1 M HCl, Cu(II) is co-deposited with tellurium at − 0.5 V in the form of a Cu-Te alloy. When SW-ASV is used, Cu(II) accumulated in-situ with Te(IV) on the GC electrode yields a stripping peak at a potential ca. 240 mV more positive than that obtained at a bare GC; this peak is also 3.65 times higher. The key parameter that determines the performance of the TeF/GC electrode in the ASV determination of Cu(II) is the concentration of Te(IV) present in the supporting electrolyte. For higher concentrations of Cu(II) in the range from 25 to 125 μg L −1 and a time of accumulation equal to 60 s, the Te(IV) concentration of 150 μg L −1 is recommended. In the Cu(II) concentration range from 0.5 to 25 μg L −1 and a longer accumulation time of 300 s, 50 μg L −1 of Te(IV) is optimal. These conditions allow a relatively positive potential window to be applied and, consequently, make the TeF/GC electrode a viable alternative to the BiFE and SbFE in the determination of Cu(II) traces via anodic stripping voltammetry. The application of the tellurium film electrode under the optimized conditions (supporting electrolyte containing 0.1 M HCl and 50 μg L −1 Te(IV), 300 s of accumulation at −0.5 V, square wave voltammetric mode) assures a sensitive stripping voltammetric response for Cu within the concentration range of 0.5 to 25 μg L −1 , good precision (RSD = 4%), and a low detection limit (0.18 μg L −1 Cu). Possible interferences from the co-existing ions and surface-active substance were investigated. The proposed method of copper determination was successfully applied and validated with the use of mineral water sample. [ABSTRACT FROM AUTHOR]

An anodic stripping voltammetry (ASV) sensing platform which provides real time determination of zincate diffusion through membrane separators in alkaline electrolyte with total experimental times on the order of hours is presented. Advanced separators are essential for future rechargeable alkaline zinc batteries. In order to be screened, these membranes need to be evaluated for their zincate blocking performance. Current complexometric titration and elemental analysis methods for zincate membrane diffusion characterization can take days to weeks to obtain results as well as include large sample dilution factors and require additional sample processing. The anodic stripping voltammetry (ASV) sensing platform presented here provides real time determination of zincate diffusion in alkaline electrolyte with total experimental times on the order of hours. This method eliminates the need for sample dilution and post experiment sample processing. This technique significantly increases the throughput for the screening of advanced alkaline battery separators resulting in rapid turnaround times in the analysis of these vital membranes. To evaluate the utility of this method, zincate diffusion through commercial Celgard 3501 and Cellophane 350P00 was monitored using both ASV and inductively coupled plasma-mass spectrometry (ICP-MS) methods. The obtained zincate diffusion coefficients for both techniques were found to compare favorably. [ABSTRACT FROM AUTHOR]

This paper describes stable and highly dispersed aqueous colloids of polyaniline (PANI) nanofibers that were prepared by a chemical method and used to modify a glassy carbon electrode (GCE). The materials combines the good electrical conductivity and network structure of PANI nanofibers with the complexing capacity of mercaptosuccinic acid. The modified GCEs exhibit high sensitivity to Cd(II) and Pb(II) ions, with detection limits of 50 ng·L and 200 ng·L, respectively. The modified GCE was applied to the simultaneous determination of the cancer biomarkers carcinoembryonic antigen (CEA) and alpha-fetoprotein (AFP) by using particles of metal-organic frameworks (MOFs) prepared from Pb(II) or Cd(II) and 2-aminoterephthalic acid. The particles are used as electrochemical labels for secondary anti-CEA and secondary anti-AFP antibody in a sandwich assay. The two ions in the MOFs labels on the secondary antibody can be detected best at voltages of −0.63 and −0.88 V (vs Ag/AgCl), respectively. The assay has a linear response in the 0.3 pg·mL to 3 ng·mL concentration range of both CEA and AFP, and the respective detection limits are 0.03 pg·mL and 0.1 pg·mL. In our preception, this assay has a wide scope in that it may be applied to a variety of sandwich types of immunoassays. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical behaviors of Cd2+ and Pb2+ on the proposed mesoporous carbon microspheres/mefenamic acid/nafion modified glassy carbon electrode (MC/MA/Nafion/GC) studied by square wave anodic stripping voltammetry (SWASV). The prepared material is characterized by XRD, SEM, FTIR, RAMAN and BET analysis. Experimental parameters, such as the deposition potential and time, the pH value of buffer solution were optimized. Under the optimized conditions, the electrode responded linearly to Cd2+ and Pb2+ in the concentration range from 50 to 300 nM, and the detection limits were 24.2 and 11.26 nM respectively. The sensitivity determined was 0.0623 μA/nM (Cd2+) and 0.192 μA/nM (Pb2+). Multiple metal ion detection with clear demarcation of peaks was produced by the electrode. Moreover, the modified electrode has possessed good selectivity and reproducibility of Cd2+ and Pb2+ detection. We also investigated the interference of various anions and surfactants for the detection of Cd2+ and Pb2+ ions. Finally the modified electrode was used to detect the presence of metal ions in practical samples and the results obtained are comparatively good with respect to AAS. [ABSTRACT FROM AUTHOR]

The authors describe a liquid crystal polymer (LCP) based bismuth (Bi) film electrode that can be directly deployed for in-situ determination of zinc(II) ions. The use of an LCP warrants improved operational reliability, high durability, and flexibility of the sensor, allowing it to be mounted on any flat or shaped surface. Square wave anodic stripping voltammetry shows the sensor to be able to detect Zn(II) (−1.64 V vs. thin-film Ag/AgCl reference electrode) in concentrations as low as 1.22 nM at a deposition time of 180 s. Other figures of merit include (a) an analytical sensitivity of 1.55 nA∙nM∙mm, (b) a linear detection range extending from 4.59 to 1071 nM, (c) a repeatability with a relative standard deviation of 3.35% (for n = 10), (d) a reproducibility with a relative standard deviation of 1.64% (for n = 6). Real-time applicability of the sensor for in-situ detection was demonstrated by determination of Zn(II) in seawater. In an extension of the method, a flexible sensor array consisting of four LCP-based sensors was attached to the hull of an autonomous kayak, which was remotely operated. The response of the sensor array indicated a clear trace of Zn(II) concentrations in seawater. This was confirmed by ICP-MS analysis. The results suggest the potential usage of the flexible LCP electrochemical sensor for in-situ monitoring. [ABSTRACT FROM AUTHOR]

Chemically-modified Indium Tin Oxide (ITO) coated glass substrates were fabricated by depositing Nafion thin films doped with tris (2,2'-bipyridyl) ruthenium(II) dichloride hexahydrate via drop coating deposition technique. The Nafion volume concentration in the film is 1% (v/v) and the mediator concentration is 5 mg per 1 mL Nafion. The chemically-modified electrodes were characterized by cyclic voltammetry (CV) and were used as working electrodes to detect varying concentrations of copper (Cu2+) and zinc (Zn2+) in a 0.1 M NaCl supporting electrolyte solution via Anodic Stripping Voltammetry (ASV). Cu2+ and Zn2+ ions were successfully determined by ASV. The limits of detection for Cu2+ and Zn2+ were 0.1 ppm and 0.7 ppm, respectively. The modified electrodes were used to determine the presence of Cu2+ and Zn2+ in different real water samples. The presence of Cu2+ was successfully determined in deep well, lake, and tap water samples, while the presence of Zn2+ was successfully determined in sea and tap water samples. Atomic Absorption Spectroscopy (AAS) results confirm the presence of Cu2+ and Zn2+ in the samples. [ABSTRACT FROM AUTHOR]

A sensitive and selective electrochemical sensor based on thioglycolic acid intercalated Mg–Al LDH (Mg–Al–TGA LDH) modified electrode was described for the determination of trace mercury using square wave anodic stripping voltammetry (SWASV). The morphology and structure of the synthesized LDHs were characterized using transmission electron microscopy, Fourier transform IR and X–ray diffraction. Several variables affecting the stripping peak current such as the supporting electrolytes, pH value, deposition potential and deposition time, were carefully optimized. Under optimal conditions, the proposed sensor exhibited a wider linearity range from 2.0 to 800 nM Hg(II) with a detection limit of 0.8 nM (S/N = 3), which was below the guideline values in drinking water given by the World Health Organization. The effect of some potentially interfering ions were also investigated and results indicated that the presence of major cations and anions has no obvious influence on the determination of Hg(II). This newly prepared sensor was successfully applied to determination of Hg(II) in water samples with good recovery, ranging from 97 to 104%. [ABSTRACT FROM AUTHOR]

The preparation of nanostructured bismuth film electrode (nsBiFE) via ex-situ multi-pulse galvanostatic deposition protocol is presented. The nsBiFE was prepared on a glassy carbon substrate electrode and studied for anodic stripping voltammetric detection of trace metal ions. Several important parameters were examined and optimized, such as the composition of plating solution, pulse deposition current, pulse duration (pulse deposition time and relaxation time) etc. The nsBiFE exhibited excellent sensitivity associated with well-defined and reproducible signals of both test analytes, i.e. Cd(II) and Pb(II), accompanied with low background contribution. It revealed good linear behaviour in the examined concentration range of 20 − 100 μg L −1 along with remarkable low limits of detection, i.e. 0.4 μg L −1 for Cd(II) and 0.1 μg L −1 for Pb(II) after 300 s accumulation, and good repeatability with RSDs of 5.1% and 3.8% for Cd(II) and Pb(II), respectively. [ABSTRACT FROM AUTHOR]

Graphene foam is one kind of network of three dimensional (3D) graphene, which inherits the properties of two dimensional graphene and overcomes the aggregation/stacking of graphene sheets. In this work, graphene foam has been characterized by scanning electron microscopy and Raman spectroscopy. A graphene foam electrode was evaluated as a new electrode material by cyclic voltammetry (CV) and used for the detection of trace level of Pb2+ by anodic stripping voltammetry (ASV). Under the optimized condition of deposition potential (-1.2 V) and deposition time (2 min), the detection limit is estimated to be 40 nM for Pb2+ based on the 3σ method. [ABSTRACT FROM AUTHOR]

A new silver nanoparticle modified screen-printed electrode was developed and applied to the simultaneous determination of Pb(II) and Cu(II). Two different types of silver nanoparticles with different shapes and sizes, Ag nanoseeds and Ag nanoprisms, were microscopically characterized and three different carbon substrates, graphite, graphene and carbon nanofibers, were tested. The best analytical performance was achieved for the combination of Ag nanoseeds with a carbon nanofiber modified screen-printed electrode. The resulting sensor allowed the simultaneous determination of Pb(II) and Cu(II) at trace levels and its applicability to natural samples was successfully tested with a groundwater certified reference material, presenting high reproducibility and trueness. [ABSTRACT FROM AUTHOR]

BiOCl-SiO2 KIT-6 composite materials with raspberry-like structures are facilely prepared under hydrothermal conditions. The mesoporous siliceous support of SiO2 KIT-6-incorporated BiOCl with enlarged yet refined surface morphology characterized by physiochemical methods exhibits an improved electrochemical performance. A sensitive electrochemical detection method of cadmium concentration using square wave anodic stripping voltammetry was developed based on BiOCl-SiO2 KIT-6 composite-modified glassy carbon electrodes, which displayed wide linear ranges of 0.5 to 10 μg/L and 10 to 300 μg/L and a detection limit of 65 ng/L. The sensitive, versatile and eco-friendly sensor was successfully applied for the determination of cadmium-spiked human blood samples. [ABSTRACT FROM AUTHOR]

We have developed an anodic stripping voltammetry method that employs carbon fiber ultra-microelectrodes modified with gold nanoparticles to determine arsenic in natural waters. Gold nanoparticles were potentiostatically deposited on carbon fiber ultra-microelectrodes at −0.90 V (vs SCE) for a time of 15 s, to form the carbon fiber ultra-microelectrodes modified with gold nanoparticles. Cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy coupled to an X-ray microanalysis system were used to check and confirm the presence of gold nanoparticles on the carbon fiber ultra-microelectrodes. Arsenic detection parameters such as deposition potential and deposition time were optimized allowing a detection range between 5 to 60 µg L -1 . The developed modified electrodes allowed rapid As determination with improved analytical characteristics including better repeatability, higher selectivity, lower detection limit (0.9 μg L -1 ) and higher sensitivity (0.0176 nA μg L -1 ) as compared to the standard carbon electrodes. The analytical capability of the optimized method was demonstrated by determination of arsenic in certified reference materials (trace elements in water (NIST SRM 1643d)) and by comparison of results with those obtained by hydride generation atomic absorption spectrometry (HG-AAS) in the determination of the analyte in tap and well waters. [ABSTRACT FROM AUTHOR]

In this study, we introduce a very sensitive and selective method for the differential pulse anodic stripping determination of Sb(III) ion on the over-oxidized poly(phenol red) modified glassy carbon electrode (PPhRedox/GCE) in 0.1 mol L-1 HCl medium. The formation of both poly(phenol red) and over-oxidized poly(phenol red) film on the electrode surfaces were characterized by electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy techniques. An anodic stripping peak of Sb(III) was observed at 0.015 V on the PPhRedox/GCE. Higher anodic stripping peak current of Sb(III) was obtained at PPhRedox/GCE compared with both bare GCE and poly(phenol red) film modified GCE (PPhRed/GCE). The calibration graph consisted of two linear segments of 0.044 - 1.218 μg L−1 and 3.40 - 18.26 μg L−1 with a detection limit of 0.0075 μg L−1. The proposed over-oxidized polymer film modified electrode was applied successfully for the analysis of antimony in different spiked water samples. Spiked recoveries for water samples were obtained in the range of 93.0-103.0%. The accuracy of the method was also verified through the analysis of standard reference materials (SCP SCIENCE-EnviroMAT™ EP−L-2). [ABSTRACT FROM AUTHOR]

The widespread use of silver nanoparticles (Ag NPs) in consumer goods has raised concerns about the release of silver in environmental waters. Of particular concern is the oxidative dissolution of Ag NPs to release Ag ions, which are highly toxic to many aquatic organisms. Here, we have investigated the application of differential pulse stripping voltammetry (DPSV) with carbon paste electrodes (CPEs) in monitoring the oxidation of Ag NPs. Using a commercially available, unmodified carbon paste and 60-s deposition times, a detection limit of 3 nM Ag could be achieved. We demonstrate its selectivity for free Ag ions over Ag nanoparticles, allowing for analysis of the oxidation of Ag NPs without the need for separation of ions and nanoparticles prior to analysis. We applied this approach to investigate the effect of pH in the oxidative dissolution of Ag NPs, demonstrating the usefulness of CPEs in studies of this type. [ABSTRACT FROM AUTHOR]

Here we demonstrate porous GaN electrode can be applied for trace Ag(I) detection. Compared to traditional planar electrodes, porous GaN electrode can detect lower concentration of Ag(I) as it possesses more deposition sites (crystal defects) and larger surface area. Under the optimum conditions, porous GaN electrode shows a linear voltammetric response in the Ag(I) concentration range from 1 to 100 ppb with the detection limit of 0.5 ppb. Such an unmodified, high-porosity and chemically stable electrode is promising to operate in real samples. [ABSTRACT FROM AUTHOR]

Copper electrodes exhibit interesting characteristics for application in electrochemical stripping analysis and represent another alternative to their mercury counterparts. In this work, we studied different types of copper-based electrodes for anodic stripping voltammetric detection of trace metal ions. We investigated copper film (CuFE), and bulk copper electrodes, such as in-situ and ex-situ prepared CuFEs using glassy carbon and screen-printed carbon supporting electrodes, a bulk copper disk and screen-printed copper electrode, and a copper wire as the simplest, inexpensive, and readily available analog. For studying their electroanalytical performances, low concentrations (μg L−1) of Cd(II) and Pb(II) were used as model ions. We examined and optimized several key parameters affecting the preparation and functioning of copper electrodes, such as the composition of the measurement solution, copper concentration for in-situ and ex-situ preparation of CuFE, deposition potential, deposition time, etc. Most of the tested copper electrodes showed favorable stripping voltammetric performances, particularly the CuFE ex-situ prepared on a glassy carbon electrode and the CuFE in-situ prepared on a screen-printed carbon substrate. Notably, a copper wire revealed an excellent electroanalytical operation with a limit of detection of 0.6 μg L−1 for Pb(II) and 1.8 μg L−1 for Cd(II). The practical applicability of a copper electrode was tested by measuring a real tap water sample. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cyclic voltammetry and amperometry used for fabrication of Bi/PXB ov.ox /GCE. • The Bi/PXB ov.ox /GCE was applied to determination of Zn(II), Cd(II) and Pb(II) in lipsticks. • The fabricated electrode showed a wide linear range and low detection limit. The presence of zinc, cadmium and lead, which affects human health even at low concentrations, in different sample matrices is of great concern. This study proposes a dependable approach for the selective and sensitive identification of these cations with an over-oxidized poly(xylenol blue) film glassy carbon electrode coated with bismuth (Bi/PXB ov.ox /GCE). Several techniques were used to chemically and physically evaluate the produced electrode surface. The following were chosen as the best conditions for determining these elements: 0.1 mol L-1 acetate buffer solution as supporting electrolyte (pH 4.5), −1.5 V accumulation potential, and 180 s accumulation duration. Under these conditions, the detection limits of Zn(II), Cd(II) and Pb(II) were found as 3.20 μg L-1, 0.21 μg L-1 and 1.98 μg L-1, respectively. Furthermore, this novel, cheap and easy-to-prepare Bi/PXB ov.ox /GCE was also successfully used for the analysis of Zn(II), Cd(II) and Pb(II) in lipstick samples. The accuracy of the voltammetric measurements was assessed by comparing them to the data acquired with inductively coupled plasma mass spectrometry, and the results were found to be consistent. [ABSTRACT FROM AUTHOR]

Because of its broad usage in industry and medical science, as well as the potential toxicity in the environment, the detection of sulfide, including hydrogen sulfide, metal sulfide and organic sulfide, has long attracted the attention of scientists working in diverse areas. Compared with other detection methods, electrochemical detection represents a highly sensitive, rapid, affordable, and simple technique. In this regard, the main objective of this report is to provide an up-to-date review of the electrochemical detection of sulfide. This review details different electrochemical approaches investigated between 2010 and 2012, together with the development of various electrodes. In addition to the commonly used techniques, such as, anodic stripping voltammetry (ASV), amperometry, cyclic voltammetry (CV), photoelectrochemical methods, and electrochemical detection methods coupled with other devices, have also been discussed, within the context of detection limit, linear detection range, and applicable conditions.

A solid waste material containing Fe(III) and other metal (hydr)oxides produced in a metal surface treatment industry has been investigated for As(V) removal. In order to facilitate sorbent application, 2% of raw material has been entrapped in calcium alginate gel matrix (2% O-CA). An accurate characterization of the sorption on gel beads was undertaken, considering thermodynamic and kinetic aspects. All experiments were carried out at pH 8, since the maximum As(V) sorption was reached between pH 6 and 9. About isotherms, the best fit was obtained considering the Langmuir model and a capacity of 1.9 mg/g was achieved. The kinetic profiles evidenced that a quantitative sorption was obtained within 10 h. The 2% O-CA beads were also tested for continuous As(V) removal in a fixed bed column. Experiments were performed at constant flow rate, and varying the inlet As(V) concentration. With a view to design an automatic system for As(V) analysis in the outlet flow, the suitability of applying Anodic Stripping Voltammetry was evaluated: the method resulted appropriated to follow the As(V) content in the outlet solutions of columns with metal inlet concentration