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Cadmium is one of the most dangerous pollutants found in the environment, where it exists mainly due to human activities. High cadmium concentrations can cause serious problems, which is why the detection and determination of Cd is one of the most important tasks. Electroanalytical methods provide rapid and accurate results in the detection of cadmium in various solutions. In this study, the possibility of using a bismuth film electrode deposited on a brass surface and electroanalytical techniques for the detection of cadmium is investigated. The bismuth film was deposited on the surface of the brass electrode using a chronoamperometric technique. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the synthesized bismuth film electrode. The current peaks obtained by anodic square-wave stripping voltammetry under optimized conditions showed a linear relationship in the investigated concentration range of cadmium. The study of the interference of different cations (Cr3+, Mn2+, Zn2+, Ca2+, K+, Mg2+ and Na+) showed that the tested cations have no influence on the determination of Cd2+ ions in the investigated solution. This finding provides a good opportunity for the use of the synthesized electrode in real samples. [ABSTRACT FROM AUTHOR]

The monitoring of heavy metals in aquatic ecosystems is of critical importance due to the toxic effects that these elements can have on wildlife and the potential risks that they pose to human health. Rivers situated in close proximity to agricultural regions are particularly susceptible to contamination from a combination of natural and anthropogenic sources. The study of bioaccumulation is of great importance for the early detection of environmental stressors. The combination of electrochemical techniques, such as square-wave anodic stripping voltammetry (SWASV), with automated flow-batch systems represents an efficient and cost-effective approach for the detection of trace metals in environmental samples. This study examines the bioaccumulation of cadmium and lead in Cyprinus carpio, a bioindicator of contamination in the Colorado River, Argentina. The fish were exposed to sublethal metal concentrations for 24, 48, and 96 h. Metal quantification was conducted using a novel automatic flow-batch system with SWASV and a bismuth film electrode. To the best of our knowledge, this constitutes the first application of this methodology on aquatic bioindicators for the assessment of metal accumulation in a natural environment. The technique demonstrated enhanced sensitivity and selectivity for the detection of trace metals. The bioaccumulation results demonstrated an increase in cadmium and lead concentrations in fish liver tissue after 96 h, reaching 10.5 µg g−1 and 11.9 µg g−1, respectively. Validation with inductively coupled plasma–atomic emission spectrometry (ICP-AES) demonstrated a satisfactory correlation, confirming the reliability of the method. This novel electrochemical approach offers enhanced accuracy and efficiency, making it a promising tool for environmental monitoring. The results indicate that Colorado River water is within safe levels for aquatic life regarding these metals. However, continuous monitoring is recommended to detect changes in contamination levels and protect ecosystem health, especially during water crises and under climate change. [ABSTRACT FROM AUTHOR]

This work presents a fast and sensitive method, with an ex–situ bismuth film screen‐printed carbon electrode (ex–situ Bi–SPCE), for the determination of Cr(VI) through adsorptive stripping voltammetry (AdSV) using Pyrogallol Red (PGR) as complexing agent. The method is based on the oxidation of PGR by Cr(VI) and posterior complexation with Cr(III). To obtain a sensitive and selective method, the effects of various parameters such as pH, ligand concentration of PGR (CPGR), accumulation potential, and accumulation time (Eacc, tacc) were optimized. The optimal conditions using Bi–SPCE prepared ex–situ were pH 4.5 (0.01 mol L−1 acetic acid/acetate buffer), CPGR: 2.6 μmol L−1, Eacc: −0.70 V and tacc: 60 s. Peak current is proportional to Cr(VI) concentration over the range 0.23–12.0 μg L−1, with a 3σ detection limit of 0.97 μg L−1. The method was validated by determining Cr(VI) in tap water spiked with Cr(VI) and Cr(III). [ABSTRACT FROM AUTHOR]

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance. [ABSTRACT FROM AUTHOR]

Heavy metals constitute pollutants that are particularly common in air, water, and soil. They are present in both urban and rural environments, on land, and in marine ecosystems, where they cause serious environmental problems since they do not degrade easily, remain almost unchanged for long periods, and bioaccumulate. The detection and especially the quantification of metals require a systematic process. Regular monitoring is necessary because of seasonal variations in metal levels. Consequently, there is a significant need for rapid and low-cost metal determination methods. In this study, we compare and analytically validate absorption spectrometry with a sensitive voltammetric method, which uses a bismuth film-plated electrode surface and applies stripping voltammetry. Atomic absorption spectroscopy (AAS) represents a well-established analytical technique, while the applicability of anodic stripping voltammetry (ASV) in complicated sample matrices such as soil samples is currently unknown. This sample-handling challenge is investigated in the present study. The results show that the AAS and ASV methods were satisfactorily correlated and showed that the metal concentration in soils was lower than the limit values but with an increasing trend. Therefore, continuous monitoring of metal levels in the urban complex of a city is necessary and a matter of great importance. The limits of detection of cadmium (Cd) were lower when using the stripping voltammetry (SWASV) graphite furnace technique compared with those obtained with AAS when using the graphite furnace. However, when using flame atomic absorption spectroscopy (flame-AAS), the measurements tended to overestimate the concentration of Cd compared with the values found using SWASV. This highlights the differences in sensitivity and accuracy between these analytical methods for detecting Cd. The SWASV method has the advantage of being cheaper and faster, enabling the simultaneous determination of heavy elements across the range of concentrations that these elements can occur in Mediterranean soils. Additionally, a dsDNA biosensor is suggested for the discrimination of Cu(I) along with Cu(II) based on the oxidation peak of guanine, and adenine residues can be applied in the redox speciation analysis of copper in soil, which represents an issue of great importance.

A simple and sensitive electrochemical sensor based on bismuth film that was coated onto a carbon paste electrode was prepared and used for hydroxymethylfurfural (HMF) detection. It was observed that bismuth film electrode (BiFE) greatly accelerated the electron transfer rate and showed excellent electrochemical activity for the oxidation of HMF compared to bare electrode. The effects of bismuth concentration, deposition potential, and deposition time on the responses of BiFE for the detection of HMF were optimized. As an analytical characteristic parameter, oxidation peak current was linearly related to HMF concentration in the range of 0.01 μM to 40 μM with a limit of detection value of 0.363 μM. Also, when selectivity studies were conducted, it was observed that BiFE had no interfering effect in the presence of three fold concentrations of coexisting similar structures compared to that of HMF. Moreover, the proposed method was successfully applied for the sensitive determination of HMF in various food samples with satisfactory recoveries. [ABSTRACT FROM AUTHOR]

Platinum dissolution in PEM fuel cells is an increasingly important indicator for the state-of-health and lifetime prediction of fuel cells in real applications. For this reason, portable online analysis tools are needed that can detect and quantify platinum with high sensitivity, selectivity, and accuracy in the product water of fuel cells. We validated the hanging mercury drop electrode (HMDE) and non-toxic bismuth film electrodes for the voltammetric determination of platinum for this purpose. Bismuth films were prepared by reductive deposition on both a glassy carbon solid state electrode and on a screen-printed electrode (film on-chip electrode). Both bismuth film electrodes could be successfully validated for the determination of platinum by adsorptive stripping voltammetry. An LOD of 7.9 μg/L and an LOQ of 29.1 μg/L were determined for the bismuth film solid state electrode, values of 22.5 μg/L for the LOD and of 79.0 μg/L for the LOQ were obtained for the bismuth film on-chip electrode. These numbers are still much higher than the results measured with the HMDE (LOD: 0.76 ng/L; LOQ: 2.8 ng/L) and are not sufficient to detect platinum in the product water of a fuel cell run in different load tests. The amount of dissolved platinum produced by a 100 W fuel cell stack upon dynamic and continuous high load cycling, respectively, was in the range of 2.9–4.1 ng/L, which could only be detected by the HMDE.

The practical application of a novel, eco-friendly electrochemical sensor based on low-dimensional structures, spherical glassy carbon microparticles, and multiwall carbon nanotubes is described. This sensor, modified with a bismuth film, was used for the determination of Cd(II) by the anodic stripping voltammetric method. The instrumental and chemical factors influencing the sensitivity of the procedure were thoroughly investigated and their most favorable values were selected (acetate buffer solution pH = 3 ± 0.1; 0.15 mmol L−1 Bi(III); activation potential/time: −2 V/3 s; accumulation potential/time: −0.9 V/50 s). Under the selected conditions, the method exhibited linearity in the range of 2 × 10−9 to 2 × 10−7 mol L−1 Cd(II) with a detection limit of 6.2 × 10−10 mol L−1 Cd(II). The results obtained also showed that the application of the sensor for Cd(II) detection did not experience any significant interference in the presence of a number of foreign ions. The applicability of this procedure was evaluated using TM-25.5 Environmental Matrix Reference Material and SPS-WW1 Waste Water Certified Reference Material as well as river water samples through addition and recovery tests. [ABSTRACT FROM AUTHOR]

Platinum dissolution in PEM fuel cells is an increasingly important indicator for the state-of-health and lifetime prediction of fuel cells in real applications. For this reason, portable online analysis tools are needed that can detect and quantify platinum with high sensitivity, selectivity, and accuracy in the product water of fuel cells. We validated the hanging mercury drop electrode (HMDE) and non-toxic bismuth film electrodes for the voltammetric determination of platinum for this purpose. Bismuth films were prepared by reductive deposition on both a glassy carbon solid state electrode and on a screen-printed electrode (film on-chip electrode). Both bismuth film electrodes could be successfully validated for the determination of platinum by adsorptive stripping voltammetry. An LOD of 7.9 μg/L and an LOQ of 29.1 μg/L were determined for the bismuth film solid state electrode, values of 22.5 μg/L for the LOD and of 79.0 μg/L for the LOQ were obtained for the bismuth film on-chip electrode. These numbers are still much higher than the results measured with the HMDE (LOD: 0.76 ng/L; LOQ: 2.8 ng/L) and are not sufficient to detect platinum in the product water of a fuel cell run in different load tests. The amount of dissolved platinum produced by a 100 W fuel cell stack upon dynamic and continuous high load cycling, respectively, was in the range of 2.9–4.1 ng/L, which could only be detected by the HMDE. [ABSTRACT FROM AUTHOR]

A novel method of determining indium has been described in this article which uses adsorptive stripping voltammetry (AdSV) and 4-(2-pyridylazo)-resorcinol (PAR) as a chelating agent or as the preconcentration agent. The measurements were performed using square-wave voltammetry by using a combined electrode system, which allows for preconcentration and stripping without opening the circuit. Ex situ plated bismuth film electrode (BiFE) was used as the working electrode. A potential-time program was developed for the inversion cycle stages based on the various factors that affect the magnitude of the inversion signal. The calibration curve was linear in a concentration range of 2·10−7 to 4·10−6 М when the pH is 4.8, accumulation potential is −700 mV, and PAR concentration is 1·10−4 M. The detection limit for the 3σ criterion with an accumulation time of 120 s was 3.5·10−9 М. Several interferences caused by Tl(I), Zn(II), Cu(II), Pb(II), Co(II), Ni(II), Mn(II), Fe(III), Cr(III) ions have been studied, and it has been shown that medium exchange procedure can effectively eliminate some interferences. It was demonstrated that the method can be applied to the determination of indium in tap water and in ITO glass sample. [Display omitted] • Adsorptive stripping voltammetry of In(III) performed with Bismuth Film Electrode. • Determination of In(III) based on its complexation with 4-(2-pyridylazo)-resorcinol. • Electrolyte solution automatically replaced using a three-in-one combined electrode. • Electrolyte replacement at the stripping step gave high sensitivity/selectivity. • Method provided high accuracy for In(III) detection in tap water and ITO glass. [ABSTRACT FROM AUTHOR]

The widespread presence of heavy metals in drinking water sources arises as a major health concern, particularly in developing countries. The development of low-cost and reliable detection techniques is identified as a societal need to provide affordable water quality control. Herein, a bismuth film-coated gold ultramicroelectrode array (BF-UMEA) was used for the detection of Pb(II) and Cd(II) in water samples via square wave anodic stripping voltammetry (SWASV). Experimental parameters such as deposition time, Bi(III) concentration, acetate buffer concentration, pH, square wave frequency, amplitude, and step potential were all varied to determine their effects on the current peak intensities of the target metal ions. Ten-fold excess in the concentration of interferences was found to cause a decrease in the stripping peak areas of Cd(II) and Pb(II) in the following order of magnitude: benzene < NaCl < Ni(II) < Cu(II). Using Box–Behnken design, the optimum SWASV parameters that provided maximum current peak areas were 14.76 Hz (frequency), 50.10 mV (amplitude), and 8.76 mV (step potential). The limits of detection of the as-prepared BF-UMEA were 5 and 7 µg L−1 for Pb(II) and Cd(II), respectively. These results demonstrate the potential use of a BF-UMEA in SWASV for the trace quantification of Pb(II) and Cd(II) in water samples.

Novel pyrolyzed photoresist carbon electrodes for electroanalytical applications have been produced by photolithographic technology followed by pyrolysis of the photoresist. A study of the determination of Ni(II) dimethylglyoximate (Ni-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified pyrolyzed photoresist electrode (Bi-PPCE) is reported. The experimental conditions for the deposition of a bismuth film on the PPCE were optimized. The Bi-PPCE allowed the analysis of trace concentrations of Ni(II), even in the presence of Co(II), which is the main interference in this analysis, with cathodic stripping square wave voltammograms characterized by well-separated stripping peaks. The calculated limits of detection (LOD) were 20 ng∙L−1 for Ni(II) alone and 500 ng∙L−1 in the presence of Co(II). The optimized method was finally applied to the analysis of certified spring water (NIST1640a).

The determination of ethyl [4-oxo-8-(3-chlorophenyl)-4,6,7,8-tetrahydroimidazo[2,1- c ][1,2,4]triazin-3-yl]acetate (ETTA), a new anticancer prodrug, using adsorptive stripping voltammetry (AdSV) was described for the first time. This method is based on adsorptive/reductive behaviour of ETTA at an in situ plated bismuth film electrode (BiFE) as a sensor. A number of experimental variables (e.g., a composition and pH of the supporting electrolyte, the conditions of bismuth film deposition, an accumulation potential and time, the scan rate, etc.) were thoroughly studied in order to achieve a high sensitivity. Experimental results under optimized conditions revealed an excellent linear correlation between the monitored voltammetric peak current and the ETTA concentration in the range of 2–50 μg L −1 following an accumulation time of 300 s. The limit of detection (LOD) for ETTA following 300 s of an accumulation time was 0.4 μg L −1 . The proposed facile, sensitive and inexpensive method was successfully applied to the determination of ETTA in serum. The investigated prodrug was extracted from serum using SPE method. [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]

The authors describe a graphite immobilized bismuth film electrode with enhanced sensitivity for the organophosphorus pesticide paraoxon. The film was formed by ex-situ electroplating of bismuth onto the large surface of a glassy carbon electrode modified with graphite nanopowder (Bi/Gr/GCE). The modified GCE was characterized by chronoamperometry using p-nitrophenol as a model nitro compound. The modification of the GCE results in an increase of the electroactive area (to 27.7 mm) and of the electrocatalytic activity (the catalytic rate constant being 4140 L·mol·s). This results in an enhancement of the current for the electroreduction of paraoxon by a factor of 4.3 (compared to a plain GCE). The modified GCE was applied to the sensitive determination of paraoxon by differential pulse voltammetry. At a typical working potential of −0.45 V vs. Ag/AgCl, the LOD is 2 nmol·L of paraoxon, which is comparable to the LOD of some cholinesterases-based electrochemical sensors and is lower than the LOD of the organophosphorus hydrolase-based electrochemical sensors for paraoxon. In addition, the new GCE is more stable than enzyme-based sensors, and it can be renewed. [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]

The construction of a low cost mini sensor containing a bismuth-film electrode (BiFE), as work electrode, a silver electrode as pseudo reference electrode, and copper as counter electrode is proposed. The application of this mini sensor using a low cost electrochemical cell for in loco voltammetric determinations of inorganic and organic analytes is also described.

The applicability of differently modified glassy carbon (GC) electrodes for direct or indirect determinations of various physiologically active compounds (insecticides and pharmaceuticals) in different formulations and some real samples was investigated. Samples of selected insecticides from the group of neonicotinoids with nitroguanidine (thiamethoxam and imidacloprid), cyanoimine (acetamiprid) and nitromethilene (nitenpyram) fragments, prepared in an appropriate manner, were determined by voltammetry on bare and surface-modified GC electrodes, while in the case of pharmaceuticals such as Trodon and Akineton, the chloride anion titration was followed using bare GC and phosphorus doped (P–GC) electrodes. The P–GC was also used to monitor the chloride content in the photocatalytic degradation of the (4-chloro-2-methylphenoxy)acetic acid herbicide. It was found that apart from the nature of the electrode material, the analyte and supporting electrolyte, as well as the pretreatment of the electrode surface essentially influences the applicability of the employed sensors.

The applicability of differently modified glassy carbon (GC) electrodes for direct or indirect determinations of various physiologically active compounds (insecticides and pharmaceuticals) in different formulations and some real samples was investigated. Samples of selected insecticides from the group of neonicotinoids with nitroguanidine (thiamethoxam and imidacloprid), cyanoimine (acetamiprid) and nitromethilene (nitenpyram) fragments, prepared in an appropriate manner, were determined by voltammetry on bare and surface-modified GC electrodes, while in the case of pharmaceuticals such as Trodon and Akineton, the chloride anion titration was followed using bare GC and phosphorus doped (P-GC) electrodes. The P-GC was also used to monitor the chloride content in the photocatalytic degradation of the (4-chloro-2-methylphenoxy)acetic acid herbicide. It was found that apart from the nature of the electrode material, the analyte and supporting electrolyte, as well as the pretreatment of the electrode surface essentially influences the applicability of the employed sensors.

A study for the application of bismuth film electrode (BiFE) under less acidic conditions for anodic stripping voltammetric measurements of Zn(II) in complex organic sample, i.e. in the cell culture medium containing ZnO nanoparticles, is presented. The BiFE was prepared in-situ on a substrate glassy carbon electrode in solution containing 0.1 mol L −1 piperazine- N , N' -bis(2-ethanesulfonic acid) (PIPES) and 0.1 mol L −1 KNO 3 as supporting electrolyte, adjusted to pH 6.5, and in the presence of dissolved oxygen. In the model solution, i.e. in the absence of cell culture medium and ZnO nanoparticles, the BiFE revealed good linear response in the examined concentration range of 10–100 μg L −1 Zn(II) with r 2 of 0.994, the LOD of 0.14 μg L −1 associated with 120 s accumulation step, and favorable repeatability of 1.7%. Upon the addition of cell culture medium, the signal of Zn(II) attenuated for ca. 64%; however, the BiFE still exhibited excellent linear response in the examined concentration range of 10–100 μg L −1 Zn(II) with r 2 = 0.999, favorably low LOD of 0.15 μg L −1 after 120 s accumulation, and satisfactory repeatability of 3.0%. Finally, the applicability of the proposed method was successfully demonstrated through measuring Zn(II) in the cell culture medium containing 5 mg L −1 of ZnO nanoparticles for the purpose of a nanotoxicological study. [ABSTRACT FROM AUTHOR]

The development of nanostructured conducting polymers based materials for electrochemical applications has attracted intense attention due to their environmental stability, unique reversible redox properties, abundant electron active sites, rapid electron transfer and tunable conductivity. Here, a phytic acid doped polyaniline nanofibers based nanocomposite was synthesized using a simple and green method, the properties of the resulting nanomaterial was characterized by electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A glassy carbon electrode modified by the nanocomposite was evaluated as a new platform for the simultaneous detection of trace amounts of Cd 2+ and Pb 2+ using differential pulse anodic stripping voltammetry (DPASV). The synergistic contribution from PANI nanofibers and phytic acid enhances the accumulation efficiency and the charge transfer rate of metal ions during the DPASV analysis. Under the optimal conditions, good linear relationships were obtained for Cd 2+ in a range of 0.05–60 μg L −1 , with the detection limit ( S / N = 3) of 0.02 μg L −1 , and for Pb 2+ in a range of 0.1–60 μg L −1 , with the detection limit ( S / N = 3) of 0.05 μg L −1 . The new electrode was successfully applied to real water samples for simultaneous detection of Cd 2+ and Pb 2+ with good recovery rates. Therefore, the new electrode material may be a capable candidate for the detection of trace levels of heavy metal ions. [ABSTRACT FROM AUTHOR]

In this paper, a Box–Behnken design (BBD) was conducted and the response surface methodology (RSM) was employed to investigate the influence to different parameters to Cd(II) detection at bismuth film/glassy carbon electrode (Bi/GCE) by Square Wave Anodic Stripping Voltammetry (SWASV), and the stripping peak current was used to evaluate the detection performance of each parameter combination. A three-level–three-factor full factorial (3 3 ) BBD has been conducted to investigate interaction effects. The relationship between stripping peak current and the three factors was quantitatively described by a multivariate regression model through the RSM. The optimal parameter combination within the studied experimental range was obtained to improve the detection performance, considering the interaction effects among Bi(III) concentration, pH and deposition potential. Under the optimal parameter combination, SWASV was applied to detect the concentration of Cd(II) on Bi/GCE, the linear calibration curve ranged from 1 to 170 μg/L with a detection limit of 0.3 μg/L (S/N = 3). The proposed analytical procedure was further applied to detect trace Cd(II) in soil samples with satisfactory results. [ABSTRACT FROM AUTHOR]

An easy, but effective, method has been proposed to detect and quantify the Pb(II) in the presence of Cd(II) based on a Bi/glassy carbon electrode (Bi/GCE) with the combination of a back propagation artificial neural network (BP-ANN) and square wave anodic stripping voltammetry (SWASV) without further electrode modification. The effects of Cd(II) in different concentrations on stripping responses of Pb(II) was studied. The results indicate that the presence of Cd(II) will reduce the prediction precision of a direct calibration model. Therefore, a two-input and one-output BP-ANN was built for the optimization of a stripping voltammetric sensor, which considering the combined effects of Cd(II) and Pb(II) on the SWASV detection of Pb(II) and establishing the nonlinear relationship between the stripping peak currents of Pb(II) and Cd(II) and the concentration of Pb(II). The key parameters of the BP-ANN and the factors affecting the SWASV detection of Pb(II) were optimized. The prediction performance of direct calibration model and BP-ANN model were tested with regard to the mean absolute error (MAE), root mean square error (RMSE), average relative error (ARE), and correlation coefficient. The results proved that the BP-ANN model exhibited higher prediction accuracy than the direct calibration model. Finally, a real samples analysis was performed to determine trace Pb(II) in some soil specimens with satisfactory results. [ABSTRACT FROM AUTHOR]

The determination of Sb(III) on an ex-situ bismuth screen-printed carbon electrode ( ex-situ BiSPCE) by means of adsorptive stripping voltammetry (AdSV) using quercetin-5′-sulfonic acid as chelating agent was optimized. The effect of different experimental parameters such pH, ligand concentration (C QSA ), accumulation potential (E acc ) and accumulation time (t acc ) were studied to obtain a wide linear range, the highest sensitivity and the lowest detection limit. Ex-situ BiSPCE was analytically compared with a sputtered bismuth screen-printed electrode (Bi sp SPE) under optimal conditions. The obtained analytical parameters suggest that ex-situ BiSPCE behaves much better than Bi sp SPE and the first was selected for this study. Optimal parameters were pH=4.6; C QSA =10.0 to 20.0×10 −6 mol L −1 ; E acc =−0.5 V and t acc =60 s. Peak area is proportional to Sb(III) concentration up to 100.0 μg L −1 (t acc 60 s) and 45.0 μg L −1 (t acc 120 s) range, with detection limits of 1.2 μg L − 1 (t acc 60 s) and 0.8 μg L −1 (t acc 120 s). The relative standard deviation for a Sb(III) solution (20.0 μg L −1 ) was 3.9% for ten successive assays. Thus, the effect of various interfering metal ions was studied and the methodology was validated using a spiked groundwater reference material with very satisfactory results. [ABSTRACT FROM AUTHOR]

A glassy carbon electrode (GCE) modified with bismuth oxide nanoparticles (BiONPs) and the chitosan (CS) was fabricated, and used to simultaneously determine lead and cadmium by differential pulse anodic stripping voltammetry. This modified electrode can be self-designed and prepared at low-costs. Scanning electron microscopy image shows that the mean diameter of BiONPs is about 235 nm. The sensitivity of the BiONPs-CS-GCE is much better than that of the bare GCE and the CS-GCE. The effects of deposition potential, pH of the solution, and deposition time were optimized. Under the optimized conditions (pH = 5.0, E = −1.7 V, t = 180 s), the composite film electrode was then applied to the analysis of lead (II) and cadmium (II). The linear range of the electrode was 0.4-2.8 μM for Pb (II) and 0.8-5.6 μM for Cd (II), with a limit of detection of 0.15 μM for Pb (II) and 0.05 μM for Cd (II), respectively. The determination of Pb (II) and Cd (II) in spiked tap water was performed and gave recoveries ranging from 99 to 122 % for Pb (II), and from 96 to 120 % for Cd (II). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Since lead is teratogenic, carcinogenic and mutagenic, people pay increasing attention to lead contamination in water environment. In this work, a novel electrochemical sensor was developed to detect Pb(II) ion in water by PPy, MOFs and bismuth film (BF) modify GCE. Scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, electrochemical impedance spectroscopy, contact angleanalyses, cyclic voltammetry and differential pulse anodic stripping voltammetry were used to characterize the BF-PPy/UIO-66-NH 2 /GCE surface, revealing the physical and electrochemical properties of the electrode. MOFs increased the specific surface area and adsorption site of the electrode. The PPy enhanced the conductivity of the composites materials. MOFs and PPy synergistically promoted the electrochemical performance of the electrode. The deposition potential, deposition time, solution pH and Bi (III) concentration were optimized to determine the optimal detection condition. The electrode has a wide linear range (0.5 to 10 μg/L) with a low detection limit (0.05 μg/L). This electrode also has good anti-interference, repeatability and stability. Besides, it has been successfully applied to the detection of actual water samples. The recovery rates ranged from 95.4 % to 102.8 % with a relative standard deviation (RSD) less than 4.40 %. Our results provide an insight on efficient and rapid detection of Pb(II) ions in water environment in the future. [Display omitted] • MOFs and polypyrrole synergistically promoted the electrochemical performance. • The fabricated BF-PPy/UIO-66-NH 2 /GCE shows a low Pb(II) detection limit. • This sensor was applied to the detection of Pb(II) in tap water and groundwater. [ABSTRACT FROM AUTHOR]

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)-cupferron complex in the differential pulse mode (detection limit of 1.0 µg L−1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L−1 for Cd (II) and 2.43 µg L−1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO3/H2O2). The following value ranges were evaluated: U (VI) 37.2-150 mg kg−1, Pb (II) 78.3-204 mg kg−1 and Cd (II) 44.1-71.6 mg kg−1. Validation was performed by using the standard reference materials SRM-695 - phosphate fertilizer - and SRM-1643e - water. [ABSTRACT FROM AUTHOR]

A straightforward protocol for measuring low concentration levels of Ag(I) using bismuth film electrode (BiFE) in combination with anodic stripping voltammetry was developed and studied as a suitable alternative to current methods for detecting the dissolution of silver nanoparticles (Ag NPs). The BiFE was prepared in-situ on the surface of a supporting glassy carbon electrode. Several key operational parameters were examined and optimized, e.g. accumulation potential, accumulation time and concentration of Bi(III). The BiFE revealed good linear operation in the examined concentration range of 10–90 μg L −1 Ag(I) with r 2 of 0.998, calculated limit of detection (3σ) of 2.1 μg L −1 obtained after 60 s accumulation, and favorable repeatability with RSD of 3.6% (50 μg L −1 , n = 10). The method was successfully tested through measuring Ag(I) in the supernatant of a commercial Ag NP suspension and the performance was superior to the potentiometric measurement using silver ion-selective electrode. [ABSTRACT FROM AUTHOR]

Two precursors of bismuth film – Bi 2 O 3 and Bi(III) ions – and a favorable orientation of the magnetic field were exploited to increase the Zn signals recorded at screen-printed electrodes modified with a bismuth layer. When using this configuration and an in-situ procedure, Zn(II) signals were better shaped and much more sensitive than those obtained for conventional bismuth-modified screen-printed electrodes. The developed procedure exhibits linear behavior from 4 to 199 μg l −1 Zn(II) with satisfying reproducibility (5%) and an low LOD of 0.05 μg l −1 . The method was applied for the determination of Zn(II) in fly ash extracts and mineral waters. [ABSTRACT FROM AUTHOR]

The determination of trace gallium using adsorptive stripping voltammetry at an in situ plated bismuth film electrode was described. The method was based on simultaneous film formation and the Ga(III)–cupferron complex preconcentration at −0.65 V and its cathodic stripping during the potential scan. The effect of Bi(III) and cupferron concentration, the influence of deposition potential and time, and the scan rate on the determination of Ga(III) were studied. A linear response in the concentration range of 3×10 −10 to 3×10 −7 mol L −1 ( r =0.998) was obtained with detection limit of 1.05×10 −10 mol L −1 using accumulation time of 180 s. Finally, the bismuth film electrode was successfully applied for the determination of Ga(III) in certified reference material seawater NASS-5 with satisfactory results. [ABSTRACT FROM AUTHOR]

This article reports a new simple and sensitive method for the determination of folic acid by adsorptive stripping voltammetry. The method is based on the accumulation of folic acid at a bismuth film plated in situ on a glassy carbon substrate. In order to stabilize bismuth ions, sodium potassium tartrate was added to the supporting electrolyte. The bismuth film formation and folic acid accumulation conditions were optimized and measurements were carried without solution deaeration. The calibration graph was linear from 5 × 10−10to 2 × 10−8 mole per liter with an accumulation time of 180 seconds with a limit of detection of 2 × 10−10 mole per liter. The relative standard deviation for 5 × 10−9 mole per liter of folic acid was 3.1 percent (n = 5). The method was successfully applied for determination of folic acid in pharmaceutical preparations. [ABSTRACT FROM AUTHOR]

Pyrolyzed photoresist carbon electrodes modified with bismuth (Bi-PPCEs) were prepared and used for the determination of trace levels of chromium. In order to lower the detection limit, the choice of the supporting electrolyte concentration and electroanalytical parameters were optimized. The adsorptive cathodic stripping voltammetric determination of Cr(VI) at Bi-PPCE was selective even in the presence in Cr(III). A detection limit of 0.1 µg L−1 was obtained after 60 s preconcentration. After oxidation with UV light and oxygen, all chromium species were oxidized to Cr(VI) and the total inorganic Cr determination is possible. Finally, Bi-PPCE was applied to trace Cr(VI) analysis in real samples such as waste water and tap water. [ABSTRACT FROM AUTHOR]

Recently, metal-organic frameworks (MOFs) and their carbon derivates have been demonstrated as new electrode modifying materials for electrochemical sensing. In this work, the first example of the detection of heavy metal ions with a MOF-derived sensing platform was presented. The platform was based on a glassy carbon electrode (GCE) modified by Nafion-bismuth/nitrogen doped microporous carbon (NMC) composite, in which the NMC was derived from a zeolitic imidazolate framework-8 (ZIF-8). The good dispersibility, large specific surface area (941 m 2 g −1 ), high nitrogen content (25.0 at.%) and good electrical conductivity of the NMC materials, as well as the synergistic effects of Nafion and bismuth-film contributed to the enhanced signals of the electrode during the differential pulse anodic stripping voltammetry (DPASV) measurements for simultaneous detection of trace Cd(II) and Pb(II) in aqueous solution. The calibration curves for Cd(II) covered two linear ranges varying from 2 to 10 μg L −1 and 10 to 100 μg L −1 . As for Pb(II), the linear calibration curves ranged from 0.5 to 10 μg L −1 and 10 to 100 μg L −1 . The detection limits were estimated to be 1.5 μg L −1 (S/N = 3) for Cd(II) and 0.05 μg L −1 (S/N = 3) for Pb(II), which were 2 times and 200 times lower than the guideline values of drinking water given by the World Health Organization (WHO), for Cd(II) and Pb(II), respectively. In addition, the good reproducibility and stability of the modified electrode offered a promising perspective for the detection of trace metal ions in practice. Compared with other porous carbon modified electrodes that obtained by either drop-casting or screen-printing method, the proposed Nafion/Bi/NMC/GCE showed a much lower detection limit for Pb(II) and a lower or comparable detection limit for Cd(II). Moreover, the obtaining of uniformly ordered N-doped carbon polyhedron could shed light on the preparation of other heteroatom-doped electrode modifying materials for the detection of heavy metal ions. [ABSTRACT FROM AUTHOR]

In order to reduce the sample consumption and waste generation for electrochemical purposes, a screen-printed electrode (SPE) used for electrodeposition of bismuth film (SPE-BiFE) and a thermostated electrochemical flow cell (EFC) were developed. The SPE-BiFE with the EFC was employed to determine Cd2+ and Pb2+ ions in natural, wastewater and tap water samples by square-wave anodic stripping voltammetry (SWASV). For this, the flow-batch analysis (FBA) approach based on solenoid micro-pumps and three-way valves was developed to carry out a fully automated procedure with temperature control. Furthermore, the FBA and the SWASV parameters were optimized, on line simultaneous determination of Cd2+ and Pb2+ ions was performed and two analytical curves were linearly acquired in the concentration ranges from 6.30 to 75.6µgL−1 and from 3.20 to 38.4µgL−1, respectively. Moreover, limits of detection of 0.60µgL−1 and 0.10µgL−1 for Cd2+ and Pb2+, respectively, were obtained. Studies of precision for the same SPE-BiFE and repeatability for five built SPE-BiFE were carried out for Cd2+ and Pb2+ ion measurements and RSD of 4.1% and 2.9% (n=3) with repeatabilities (n=5) of 6.5% and 8.0% were respectively obtained for both analytes. Besides, a low consumption of 700µL of reagents and a sampling frequency of 13h−1 were acquired. Simplicity, fast response, accuracy, high portability, robustness and suitability for in loco analyses are the main features of the proposed electroanalytical method. [ABSTRACT FROM AUTHOR]

Abstract: A new chemically modified glassy carbon electrode based on bismuth film coated mesoporous silica nanoparticles was developed and evaluated for reliable quantification of trace Pb2+ and Cd2+ by anodic stripping square wave voltammetry in natural water samples. Compared with conventional bismuth film electrodes or bismuth nanoparticles modified electrodes, this electrode exhibited significantly improved sensitivity and stability for Pb2+ and Cd2+ detection. The key experimental parameters related to the fabrication of the electrode and the voltammetric measurements were optimized on the basis of the stripping signals, where the peak currents increased linearly with the metal concentrations in a range of 2-150μgL−1 with a detect limit of 0.2μgL−1 for Pb2+, and 0.6μgL−1 for Cd2+ for 120s deposition. Good reproducibility was achieved on both single and equally prepared electrodes. In addition, scanning electron microscopy reveals that fibril-like bismuth structures were formed on silica nanoparticles, which could be responsible for the improved voltammetric performance due to the enhanced surface area. Finally, the developed electrode was applied to determine Pb2+ and Cd2+ in water samples, indicating that this electrode was sensitive, reliable and effective for the simultaneous determination of Pb2+ and Cd2+. [Copyright &y& Elsevier]

Voltammetric sensors based on bismuth film electrodes are an attractive alternative to other sensors for application in electroanalysis of heavy metals. Bismuth film electrodes can be formed by a similar method on the same substrates as mercury. These systems were used most frequently for simultaneous determination of heavy metals such as Pb, Cd and Zn by anodic stripping voltammetry. Our voltammetric sensor was fabricated on an alumina substrate. A photoresist film prepared by pyrolysis of positive photoresist S-1813 SP15 on the alumina substrate was used as an electrode support for bismuth film deposition. The influence of the Nafion membrane on the measurement sensitivity of the sensor and mechanical stability of the bismuth film were investigated. The sensor was successfully applied for determination of Pb, Cd and Zn in an aqueous solution in the concentration range of 0.2 to 10 µg L−1 by square wave anodic stripping voltammetry on an in-situ formed bismuth film electrode with Nafion-coating. Parameters of the sensor such as sensitivity, linearity, detection limit, repeatability and life-time were evaluated. In the best case, the detection limits were estimated as 0.07, 0.11 and 0.63 µg L−1 for Pb, Cd and Zn, respectively. Finally, the applicability of the sensor was tested in analysis of Pb, Cd and Zn in real samples of tap and river water using the method of standard additions. [ABSTRACT FROM AUTHOR]

The bismuth film electrode was used to record well-developed voltammograms of azo food coloring Sunset Yellow FCF (SY). The employed Bi(III)/HClO4 plating solutions produced very adhesive and mechanically stable films that were applied in both stationary and flow conditions. The influence of the dimensions of the glassy carbon support, plating solution concentration and potential was discussed. The sensitivity of SWV was sufficient to obtain a linear calibration curve for low concentration levels of SY (below 0.1 mg/L; LOD=1 µg/L, linear range 4.4-87 µg/L). The measurements in a flow system were considered as a tool for the determination of relatively high concentrations (>1 mg/L; LOD=300 µg/L, linear range 300-8800 µg/L) of SY. [ABSTRACT FROM AUTHOR]

In this work we evaluated the use of different variable selection techniques combined with partial least-squares regression (PLS) - genetic algorithm PLS (GA-PLS), interval PLS (iPLS), and synergy interval PLS (siPLS) - in the simultaneous determination of Cd(II), Cu(II), Pb(II) and Zn(II) by anodic stripping voltammetry at a bismuth film. Generally, variable selection provided an improvement in prediction results when compared to full-voltammogram PLS. The use of interval selection based algorithms have shown to be most adequate than the selection of discrete variables by GA. Excellent analytical performances were obtained despite the inherent complexity of the simultaneous determination. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sensitive square wave anodic stripping voltammetry analysis of both Pb2+ and Cd2+. [•] Glassy carbon working electrode modified with overoxidized 2-mercaptoethanesulfonate-tethered polypyrrole, Nafion and Bi. [•] Quartz crystal microbalance studies on electrode modifications and intermolecular interactions. [ABSTRACT FROM AUTHOR]

Abstract: A sensitive platform for the simultaneous electrochemical determination of Cd(II) and Pb(II) in aqueous solution has been developed based on the gold nanoparticle-graphene-cysteine composite (Au-GN-Cys) modified bismuth film glassy carbon electrode (GCE) using square wave anodic stripping voltammetry (SWASV). The synergistic effect of cysteine as well as the enlarged, activated surface and good electrical conductivity of gold nanoparticles and graphene contributed to the deposition of Cd(II) and Pb(II) on the electrode surface. Under the optimum conditions, a linear relationship existed between the currents and the concentrations of Cd(II) and Pb(II) in the range between 0.50μgL−1 to 40μgL−1 with the detection limits of 0.10μgL−1 for Cd(II) and 0.05μgL−1 for Pb(II), respectively, based on a signal-to-noise ratio equal to 3 (S/N=3). The interference experiments show that some metal cations had little influence on the SWASV signals of Cd(II) and Pb(II). In addition, the developed electrode displayed a good repeatability and reproducibility. These studies imply that the Au-GN-Cys composites might be an alternative candidate for practical applications in electrochemical detection of metal ions. [Copyright &y& Elsevier]

The bismuth-coated electrode is known to be prone to errors caused by copper(II). This study investigates copper(II) interference at bismuth film electrode for the detection of lead(II) and cadmium(II). It was conducted using glassy carbon electrode, while the bismuth film was plated in situ simultaneously with the target metal ions at − 1200 mV. Copper(II) presented in solution significantly reduced the sensitivity of the electrode, for example there was an approximately 70 % and 90 % decrease in peak signals for lead(II) and cadmium(II), respectively, at a 10-fold molar excess of copper(II). The decrease in sensitivity was ascribed to the competition between copper and bismuth or the metal ions for surface active sites. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis suggested a large decrease in the amount of bismuth nanoparticles formed on the electrode surface in the presence of copper(II) occurred, validating the competition between copper and bismuth ions for surface active sites. Recovery of the stripping signal of lead(II) and cadmium(II) was obtained by adding ferrocyanide ion to the solution. Finally, the proposed method was successfully applied to determine lead(II) and cadmium(II) in water samples and the method was validated by ICP-MS technique. [ABSTRACT FROM AUTHOR]

In this work, we reported a simultaneous determination approach for Pb(II), Cd(II) and Zn(II) at μg L −1 concentration levels using differential pulse stripping voltammetry on a bismuth film electrode (BiFE). The BiFE could be prepared in situ when the sample solution contained a suitable amount of Bi(NO) 3, and its analytical performance was evaluated for the simultaneous determination of Pb(II), Cd(II) and Zn(II) in solutions. The determination limits were found to be 0.19 μg L −1 for Zn(II), and 0.28 μg L −1 for Pb(II) and Cd(II), with a preconcentration time of 300 s. The BiFE approach was successfully applied to determine Pb(II), Cd(II) and Zn(II) in tea leaf and infusion samples, and the results were in agreement with those obtained using an atomic absorption spectrometry approach. Without Hg usage, the in situ preparation for BiFE supplied a green and acceptability sensitive method for the determination of the heavy metal ions. [ABSTRACT FROM AUTHOR]

A study on the simultaneous determination of Ni(II) and Co(II) dimethylglyoximates (Ni-DMG and Co-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified gold electrode (Bi-AuE) is reported. The key operational parameters, such as Bi(III) concentration, accumulation potential and accumulation time were optimized and the morphology of the Bi-microcrystals deposited on the Au-electrode was studied. The Bi-AuE allowed convenient analysis of trace concentrations of solely Ni(II) or of Ni(II) and Co(II) together, with cathodic stripping voltammograms characterized by well-separated stripping peaks. The calculated limit of detection ( LOD) was 40 ng L−1 for Ni(II) alone, whereas the LOD was 98 ng L−1 for Ni(II) and 58 ng L−1 for Co(II), when both metal ions were measured together. The optimized method was finally applied to the analysis of certified spring water (NIST1640a) and of natural water sampled in the Lagoon of Venice. The results obtained with the Bi-AuE were in satisfactory agreement with the certified values and with those provided by complementary techniques, i.e., ICP-OES and ICP-MS. [ABSTRACT FROM AUTHOR]