Anodic Stripping Voltammetry Measurements Research Articles

Adaptive Fabrication of Electrochemical Chips with a Paste-Dispensing 3D Printer.

Electrochemical (EC) detection is a powerful tool supporting simple, low-cost, and rapid analysis. Although screen printing is commonly used to mass fabricate disposable EC chips, its mask is relatively expensive. In this research, we demonstrated a method for fabricating three-electrode EC chips using 3D printing of relatively high-viscosity paste. The electrodes consisted of two layers, with carbon paste printed over silver/silver chloride paste, and the printed EC chips were baked at 70 °C for 1 h. Engineering challenges such as bulging of the tubing, clogging of the nozzle, dripping, and local accumulation of paste were solved by material selection for the tube and nozzle, and process optimization in 3D printing. The EC chips demonstrated good reversibility in redox reactions through cyclic voltammetry tests, and reliably detected heavy metal ions Pb(II) and Cd(II) in solutions using differential pulse anodic stripping voltammetry measurements. The results indicate that by optimizing the 3D printing of paste, EC chips can be obtained by maskless and flexible 3D printing techniques in lieu of screen printing.

Effect of dissolved organic matter on copper bioavailability to a coastal dinoflagellate at environmentally relevant concentrations

The speciation and bioavailability of copper (Cu) in the marine environment are affected by the presence of dissolved organic matter (DOM). Previous studies conducted at dissolved Cu concentrations >100 nM confirmed that Cu bioavailability depends on the concentration of labile Cu, as measured by anodic stripping voltammetry (ASV), which aligns with the expectations of the biotic ligand model (BLM). However, ambient Cu concentrations in coastal waters are generally lower, ranging between 1 and 80 nM, and the effect of DOM on the bioavailability of Cu to marine organisms has not been tested within that range of Cu concentrations. The present study aims to assess the impact of two types of DOM, a commercially available fulvic acid, and marine DOM extracted by ultrafiltration, on Cu bioavailability to phytoplankton using short-term 65Cu internalisation by the marine dinoflagellate Prorocentrum micans. Results showed that Cu internalisation decreases with DOM additions as expected according to the BLM and in agreement with ASV measurements of labile Cu, at the highest tested Cu concentration (100 nM). On the contrary, at a lower Cu concentration (20 nM), organic complexes appear to be partially bioavailable, thereby challenging the general applicability of the BLM model at environmentally relevant concentrations in coastal areas.

Thin Film Electrodes for Anodic Stripping Voltammetry: A Mini-Review.

Anodic stripping voltammetry (ASV) is a powerful electrochemical analytical technique that allows for the detection and quantification of a variety of metal ion species at very low concentrations in aqueous media. While early, traditional ASV measurements relied on macroscopic electrodes like Hg drop electrodes to provide surfaces suitable for plating/stripping, more recent work on the technique has replaced these electrodes with thin film metal electrodes generated in situ. Such electrodes are plated alongside the analyte species onto the surface of a primary electrode, producing a composite metal electrode from which the analyte(s) can then be stripped, identified, and quantified. In this minireview, we will explore the development and use of these unique electrodes in a variety of different applications. A number of metals (e.g., Hg, Bi, Sn, etc.) have shown promise as thin film ASV electrodes in both acidic and alkaline media, and frequently multiple metals in addition to the analyte of interest are deposited together to optimize the plating/stripping behavior, improving sensitivity. Due to the relatively simple nature of the measurement and its suitability for a wide range of pH, it has been used broadly: To measure toxic metals in the environment, characterize battery materials, and enable biological assays, among other applications. We will discuss these applications in greater detail, as well as provide perspective on future development and uses of these thin film electrodes in ASV measurements.

A vibrating membrane working electrode for highly sensitive anodic stripping voltammetry

Anodic stripping voltammetry (ASV) is an effective electrochemical method for quantitative determination of ions in solution. In this work, we present a new vibrating working electrode for the ASV detection of copper ion. This working electrode is a thin multilayer membrane consisting of a gold film working electrode evaporated on a piezoelectric resonant diaphragm. Chemical vapor deposition and electron beam evaporation methods are used to form multiple functional layers in the membrane. Vibrational and electrochemical properties of the membrane working electrode are experimentally investigated. In the ASV measurement, the vibration of the piezoelectric diaphragm can enhance the mass transfer rate during the metal deposition step. The sensitivity of sensors under vibration is improved by 4 times, compared with those at static conditions. The detection limit with and without vibration are 0.37 and 1.66 μg/L respectively at a deposition time of 5 min. In addition, the experimental results in this study also indicate the stripping peak current is influenced by the vibrating velocity and mode shape of the piezoelectric diaphragm. The vibrating membrane electrode presented in this study can be potentially used to different types of electrochemical sensing applications limited by the mass transfer rate of the analyte.

Effect of Hydrazine on Formation of Bismuth Nanoparticles and its Properties as Pb Sensors

Bismuth nanoparticles (BiNPs) are of interest in many applications such as imaging, antimicrobial agent, biosensors and electrochemical electrodes. However, synthesis of pure bismuth is difficult as bismuth tend to oxidise and form bismuth oxide that affects its properties. In this work, BiNPs were synthesised using hydrothermal method in an autoclave at 160°C. The effect of hydrazine (N2H4•H2O) volume as reducing and capping agent was studied from 1.0-2.5ml with 3.6 Bi(NO3)3: 4.2 Polysodium 4-Styrene-Sulfonate: 50 H2O (mass ratio). The produced BiNPs was used to modify indium tin oxide (ITO) substrates and tested as electrochemical heavy metal sensors to detect Pb and As. Pure BiNPs were successfully produced in all hydrazine volume. However, size and crystallinity of BiNPs were influenced by volume of hydrazine. Among these changeable compositions, the mass ratio of Bi(NO3)3 to N2H4•H2O is the most important factor to form uniform size and shape of BiNPs. The addition of the reducing agent, N2H4•H2O into the precursor solution promoted the subsequent reduction of Bi(III) and enabled the growth of BiNPs. Cyclic voltammetry (CV) in 0.002 mol/L of K3Fe(CN)6 electrolyte showed peak current responses obtained for BiNPs/ITO modified electrodes are larger than the bare ITO electrode, which were attributed to the fact that the electrochemical activities of ITO electrode increased by BiNPs surface modification. Stripping current responses of the Differential Pulse Anodic Stripping Voltammetry measurements were recorded for the determination of Pb(II) after a 300 seconds of deposition time at −1.2 V in 0.002 mol/L of acetate buffer solution with pH 4.5. Sensitivity response for the detection of Pb(II) was achieved in the range from 2.5 to 100 μg/L. The limit of detection (LOD) is 2.5 μg/L for Pb(II).

Antibacterial durability and biocompatibility of antibacterial-passivated 316L stainless steel in simulated physiological environment

Stainless steel (SS) has been widely applied as one of the most efficient implant metal materials, although corrosion and infection in body environment are still challenging. Herein, an antibacterial passivation method was employed to enhance the antibacterial performance and corrosion resistance of the medical 316L SS. The result proved that the antibacterial-passivated 316L SS exhibited stable antibacterial activity and effectively inhibited the formation of bacterial biofilm. Electrochemical measurements combined with X-ray photoelectron spectroscopy technique were used to study the corrosion resistance and semiconductor behavior of passivated 316L SS immersed in simulated physiological environment. The results indicated that the 316L SS after antibacterial passivation treatment for 1 h, soaking in the medium for 10 days, showed satisfactory corrosion resistance attributing to proper Cu deposition in the passive film. The anodic stripping voltammetry measurement further confirmed that the Cu-bearing passive film could continuously release Cu ions into medium. The zebrafish test demonstrated an excellent in vivo biocompatibility for the 316L SS with antibacterial passivation for 0.5 and 1 h, respectively. In addition, changes of surface roughness, contact angle and chemical composition after antibacterial passivation played an important role in explaining the antibacterial mechanism, which could be clearly divided into contact killing and ionic release killing. Hence, the antibacterial passivation treatment was preliminarily proved as a potential way for enhancing the persistent antibacterial activity and corrosion resistance of 316L SS.

Nanostructured nitrogen doped diamond for the detection of toxic metal ions

This work demonstrates the applicability of one-dimensional nitrogen-doped diamond nanorods (N-DNRs) for the simultaneous electrochemical (EC) detection of Pb2+ and Cd2+ ions in an electrolyte solution. Well separated voltammetric peaks are observed for Pb2+ and Cd2+ ions using N-DNRs as a working electrode in square wave anodic stripping voltammetry measurements. Moreover, the cyclic voltammetry response of N-DNR electrodes towards the Fe(CN)6/4-/Fe(CN)6/3- redox reaction is better as compared to undoped DNR electrodes. This enhancement of EC performance in N-DNR electrodes is accounted by the increased amount of sp2 bonded nanographitic phases, enhancing the electrical conductivity at the grain boundary (GB) regions. These findings are supported by transmission electron microscopy and electron energy loss spectroscopy studies. Consequently, the GB defect induced N-DNRs exhibit better adsorption of metal ions, which makes such samples promising candidates for next generation EC sensing devices.

Graphene and Au NPs co-mediated enzymatic silver deposition for the ultrasensitive electrochemical detection of cholesterol

Cholesterol is an essential ingredient in mammals, and serum cholesterol is a major component of atherosclerotic plaques. The level of cholesterol in human serum has become an important index for clinical diagnosis and prevention of cardiovascular disease. In this paper, a simple and ultrasensitive cholesterol biosensor based on graphene oxide (GO) and gold nanoparticles (Au NPs) co-mediated enzymatic silver deposition was designed by immobilizing cholesterol oxidase (CHOD), cholesterol esterase (CHER) and GO onto the surface of Au NPs modified screen-printed carbon electrode (SPE). Under the synergistic effect of CHER, CHOD and GO, the cholesterol was hydrolyzed to generate hydrogen peroxide, which can reduce the silver (Ag) ions in the solution to metallic Ag which deposited on the surface of Au NPs modified SPE. The ultrasensitive detection of cholesterol was achieved by anodic stripping voltammetry measurement of the enzymatically deposited Ag. Under optimal conditions, the anodic stripping peak current of Ag increased with the increasing cholesterol concentration in the range from 0.01μg/mL to 5000μg/mL with a limit of detection of 0.001μg/mL (S/N = 3). In addition, the ultrasensitive cholesterol biosensor exhibited higher specificity, acceptable reproducibility and excellent recoveries for cholesterol detection.

Wireless Point-of-Care Platform With Screen-Printed Sensors for Biomarkers Detection

Measurement systems for early and reliable detection of degenerative diseases, such as Alzheimer’s disease (AD), are extremely important in clinical diagnosis. Among these, biochemical assays represent a commonly used method to distinguish patients from healthy population thanks to the sensitive recognition of specific biomarkers in biological fluids. In order to overcome actual limitations of these techniques in term of cost, standardization, and sensitivity, this study aimed to realize a low-cost highly sensitive portable point-of-care (PoC) testing system based on screen-printed electrochemical sensors. The development of the platform specifically included both the design of the sensing probe and the electronic circuit devoted to condition and acquires the transduced electric signal. The designed circuit was implemented in a printed circuit board and interfaced to a wireless system based on bluetooth data transmission in order to improve the portability of the proposed solution. Preliminary results were obtained by using controlled concentrations of electrolytic solutions and calibrating the sensors for antibodies and for a well-known protein (i.e., interleukin 8) quantified by anodic stripping voltammetry (ASV). Findings from ASV measurements showed a sensitivity of $38~\mu \text{A}$ /(ng/ml) with a tested range from 1.25 to 20 ng/ml, with a limit of detection of 2 ng/ml. Further investigation will include the validation of this PoC device by testing the concentration of a specific p53 protein isoform, which was recently identified to early correlate to AD development.

Design of a new nanocomposite between bismuth nanoparticles and graphene oxide for development of electrochemical sensors

This study describes a new route for preparation of a nanocomposite between graphene oxide (GO) and bismuth nanoparticles (BiNPs) and its evaluation as modifier electrode for development of electrochemical sensors. BiNPs were synthesized under ultrasound conditions using Bi(NO3)3 as metal precursor and ascorbic acid (AA) as reducing agent/passivating. Some experimental parameters of BiNPs synthesis such as Bi3+:AA molar ratio and reaction time were conducted aiming the best voltammetric performance of the sensor. Glassy carbon electrodes (GCE) were modified by drop-casting with the BiNPs dispersions and anodic stripping voltammetry measurements were performed and revealed an improvement in the sensitivityfor determination of Cd(II) and Pb(II) compared to an unmodified electrode. The best electrochemical response was obtained for a BiNPs synthesis with Bi3+:AA molar ratio of 1:6 and reaction time of 10min, which yielded Bi metallic nanoparticles with average size of 5.4nm confirmed by XRD and TEM images, respectively. GO was produced by graphite oxidation using potassium permanganate and exfoliated with an ultrasound tip. GO-BiNPs nanocomposite was obtained by a simple mixture of GO and BiNPs dispersions in water and kept under ultrasonic bath for 1h. GCE were modified with a nanocomposite suspension containing 0.3 and 1.5mgmL−1 of GO and BiNPs in water, respectively. Under optimized conditions, the proposed nanocomposite was evaluated on the voltammetric determination of Pb (II) and Cd (II), leading to a linear response range between 0.1 and 1.4μmolL−1 for both cations, with limit of detection of 30 and 27nmolL−1, respectively. These results indicate the great potential of the GO-BiNPs nanocomposite for improving the sensitivity of voltammetric procedures.

Detection of Heavy Metals By Anodic Stripping Voltammetry Using Nanocarbon Thin Film Electrodes in an Electrochemical Flow Cell

It is important to detect and quantify toxic heavy metals such as Pb in order to prevent damaging human health by their toxicities. A very small amount of heavy metals are included in food or water. The contamination of heavy metals into air, drinking waters, wastewaters and foods sometimes poses a serious threat to the problems on global health and environment. Conventional methods for the detection of heavy metals, such as atomic adsorption spectrometry, inductively coupled plasma mass spectrometry, and neutron activation analysis, require expensive and sophisticated instruments with the complicated sample preparation. Therefore, a simple, inexpensive and high performance analyzer for heavy metals is strongly desired. Anodic stripping voltammetry (ASV) is a standard methods for the analysis of heavy metals, because of several advantages, including high cost performance, high sensitivity resulted by its preconcentrating process, and suitability for a miniaturized system. In ASV, mercury film electrodes and the hanging mercury drop electrode had been widely used as the working electrode. However, more environmentally friendly electrode materials for use in ASV working electrodes has been strongly required, because of the increasing toxic risks on the used/disposed mercury. Here, an ASV-based Pb detection method using a nanocarbon thin film electrode with an electrochemical flow cell has been developed. The nanocarbon thin films were formed by unbalanced magnetron (UBM) sputtering, which is an exceptionally versatile technique for the deposition of high quality, well adhered films. UBM sputtering can be used to fabricate the hard films on silicon wafers that indicate the abrasion resistance and the sliding properties. The nanocarbon thin films comprise two types of carbon structure, diamond (sp3) and graphite (sp2), which have excellent properties including a wide potential window, the good electrode activity, and the superior stability. The sp2/sp3 ratios of nanocarbon thin films were adjusted by the tuning of the ion irradiation energy between a silicon substrate and a carbon target. The surface fouling of the nanocarbon films were significantly suppressed because of extremely flat surface. It is the very suitable material for the ASV measurement of heavy metals such as Pb. A flow-type ASV-based Pb-detection method was studied. The flow cell was equipped with three electrodes consisted of nanocarbon film working electrode, an Ag/AgCl reference electrode with 3M NaCL inner solution and a SUS-type counter electrode. The flow cell was designed in smaller size that has a micrometer sized thin layer around the working electrode in order to increase the concentration efficiency. Measuring samples were adjusted to pH 5.0 by the addition of acetic acid solution, and s introduced into flow cell at a flow rate of 0.03 ml min-1 by using a syringe pump. The limits of detection was 5 µg l-1 for Pb in a concentrating time of 3 min. Although this nanocarbon film electrode can be used in ASV measurement, quantitative measurement is difficult when the interfering components such as Cu are existed in sample. Since Cu is the most serious interfering component in the ASV measurement for Pb, Cu ions must be removed in a pretreatment process by using chelating resin column method or electrochemical method. However, the chelating resin method had the problems including the complicated apparatus or the frequently maintenance. The flow cell system for removing the effects by the coexisting Cu was developed. The removal cell was preferably a simple structure to prevent the fouling and clogging, and equipped with a working electrode and a counter electrode by using the nanocarbon thin films. Since it was possible to concentrate only Cu at more positive potential than Pb, the coexisting Cu was deposited on the removal working electrode. In order to increase the removal rate of Cu, it is important to design a cell to efficiently deposit copper on the electrode. The removal flow cell was designed to have the thin layer around the working electrode similar to the measurement flow cell. For the solution including 1 mg l-1 of Cu, we have succeeded in Cu removal more than 90 % by selecting the appropriate potential. It was confirmed that the removal of Cu to a concentration does not affect the measurement of Pb by using a simple mechanism. The Cu removal before measuring showed the good performances in Pb measurement.

Au Nanoparticle-Embedded Carbon Films for Electrochemical As(3+) Detection with High Sensitivity and Stability.

Au nanoparticle (AuNP)-embedded carbon films were formed with a one-step reproducible process by using unbalanced magnetron (UBM) cosputtering to make it possible to detect As(3+) in water. The sputtered Au components formed NPs (typically 5 nm in diameter) spontaneously in the carbon films, owing to the poor intermiscibility of Au with carbon. The surface contents of embedded AuNPs in the carbon film were widely controllable (Au = 13-21 at %) by regulating the target powers of Au and carbon individually. The obtained film had a flat surface (Ra = 0.1 nm) despite the fact the AuNPs were partially exposed at the surface. By anodic stripping voltammetry (ASV) As(3+) detection, a limit of detection of 0.55 ppb and linear dynamic range of 1-100 ppb were obtained with our electrode. These values meet the requirements imposed by international regulation. Moreover, our electrode structure realized good electrode stability for repetitive ASV measurements (relative standard deviation (RSD) = 11.7%, n = 15) because the partially embedded AuNP structures prevented the AuNPs from detaching from the surface. This result was achieved by the electrode recovery only by a potential scan from 0.1 to 1.5 V. Our electrodes can be stocked for a long time (2 years) with maintaining the electrode performance, which is very attractive for practical electrode. Selectivity test by using Tsukuba tap water added 10 ppb As(3+) and 1000 ppb Cu(2+) was successfully achieved with existence of 0.1 M EDTA (RSD = 2.6%, n = 3). The ASV results with tap water samples agreed well with those by the conventional ICPMS method.

Effect of the sp(2)/sp(3) Ratio in a Hybrid Nanocarbon Thin Film Electrode for Anodic Stripping Voltammetry Fabricated by Unbalanced Magnetron Sputtering Equipment.

The effect of the sp(2)/sp(3) ratio in an unbalanced magnetron sputtered nanocarbon film electrode was studied for determining Cd(2+) and Pb(2+) by anodic stripping voltammetry (ASV). The signal-to-noise ratio in the ASV measurement improved as the sp(3) concentration in the carbon film increased because the noise current decreased with the increasing sp(3) concentration. The detection limits with a carbon film containing 50% sp(3) were 0.25 and 1.0 μg L(-1) for Cd(2+) and Pb(2+) with high repeatability (Cd: 4.6% and Pb: 6.4%, n = 3). For a real sample measurement, a pretreatment system combining a photooxidation reactor and a cation exchange column was used to eliminate the interference from EDTA and Cu(2+), which forms a stable complex or alloy with Cd(2+) and Pb(2+). More than 99% of the interference was eliminated, and accurate signal currents for Cd(2+) and Pb(2+) were successfully obtained with the pretreatment system.

Robotic heavy metal anodic stripping voltammetry: ease and efficacy for trace lead and cadmium electroanalysis

A novel strategy for the automation of trace lead (Pb2+) and cadmium (Cd2+) anodic stripping voltammetry (ASV) is described. This was achieved using an electrode assembly comprising a small standard reference electrode, a Pt wire counter electrode, and an in situ bismuth-plated pencil lead working electrode for ASV in a robotic device adapted for measurements in a 24-well microtiter plate format. The movement of the electrode assembly through individual wells was by computer-controlled micropositioning, and each microtiter plate run included a sequence of electrode pretreatment, water rinsing, and simultaneous Pb2+ and Cd2+ ASV measurements. Analyte concentrations down to 2 μg/L (Pb2+) and 20 μg/L (Cd2+) could be measured in drinking and tap water, a wastewater reference material and a soil sample, with an accuracy and standard deviation typical of stripping analysis. This robotic electrochemical strategy offers automated trace metal analysis with simple instrumentation and is suggested as an option for routine use in analytical laboratories such as those providing environmental heavy metal testing services.

Cheap in situ voltammetric copper determination from freshwater samples

Detection of low concentrations of heavy metals in environmental samples is of particular interest because most of them represent persistent, highly toxic pollutants. Cu2+ detection in environmental samples is important because it is typical heavy metal, being an essential element for human beings but at higher concentrations it can create health risks. Due to the accumulation steps involved, anodic stripping voltammetry (ASV) is one of the most sensitive techniques used for the detection of low concentrations of metal ions form different environmental samples. In order to minimize sample loss during sample collection, storage and transportation it is of particular interest to perform in situ rapid and reliable routine analysis. In the present paper we describe the use of a simple, disposable pencil graphite electrode (PGE) for the determination of Cu from river water samples by mercury film anodic stripping voltammetry. The investigated water samples were collected during a period of 3 years (2009-2011), from six sampling points situated along the lower part of the Prut River (Romania). ASV measurements were performed in the presence of Hg 2+ in 0.1 M HNO3 at a carbon pencil graphite working electrode. Standard addition method was applied for the quantification of Cu 2+. The Cu 2+ content of the most river water samples analysed exceeded 2 ⎧g/L (MEWM, 2006), the maximum admitted concentration for surface waters, and these could be due to the anthropogenic activities in the region (e.g. the largest steel factory in Romania is located in the vicinity of the sampling area). Samples show an additional importance as the region is included in a protected area, Lower Prut Floodplain Natural Park, and trace elements transfer along the aquatic food chain has been previously documented (Matache et. al, 2012). The results obtained by ASV on PGE agreed well with those obtained by inductively coupled plasma atomic emission spectrometry (ICP-AES) using the Romanian standard SR ISO 11885-09. The sensor used in this work has shown some important advantages such being cheap, sensitive and able to generate reproducible results using a simple and direct electrochemical protocol. By using this type of disposable working electrodes and a portable electrochemical analysis system the developed method can be applied to the determination of copper ions directly at the sampling point.

Use of Carbon Paste Electrode Modified with Biomass for Studying the Equilibria, Kinetics, and Proton Exchange Processes Associated with Bioaccumulation

AbstractThe sorption of Cd2+ onto nonliving Typha latifolia roots was investigated using carbon paste electrodes modified with a powder formed from the ground dried root. The equilibria, kinetics, and proton exchange processes associated with the biosorption process were determined. Cd2+ was found to accumulate on the root‐modified electrode under open circuit conditions, and the electrode was transferred to an electrochemical cell for square wave anodic stripping voltammetry measurements. The measured currents were proportional to the amount of Cd2+ adsorbed onto the root, which permitted the biosorption process to be measured as a function of cadmium solution concentration, time, and pH. The equilibrium values were fit to the Langmuir or Freundlich equations, and that the Langmuir isotherm model was found to provide a better fit than the Freundlich model. The pH‐dependent sorption curves showed that the accumulation of cadmium proceeded with proton exchange, and each adsorbed cadmium ion resulted in expulsion of two protons. The sorption kinetics were studied, the data obtained were fit to two models: a pseudo‐second‐order model and an intraparticle diffusion model. The pseudo‐second‐order model provided the best description of the bioadsorption data. These results indicated that these methodologies have clear advantages over existing methods, because the amount of reagents and sorbent used for the experiments are much less than are required for batch experiments.

An sp2 and sp3 Hybrid Nanocrystalline Carbon Film Electrode for Anodic Stripping Voltammetry and Its Application for Electrochemical Immunoassay

A hybridized nanocrystalline carbon film electrode consisting of sp(2) and sp(3) bonds was investigated to reveal the reduction properties of Cd(2+) and for application as a highly sensitive and reliable electrochemical immunoassay. Conductive nanocrystalline carbon film consisting of about 60% sp(2) and 40% sp(3) bonds was fabricated using electron cyclotron resonance (ECR) sputtering equipment, and then the Cd(2+) concentrations were measured with an ECR sputtered carbon (ECR nano-carbon) electrode by employing an anodic stripping voltammetry (ASV) technique. The preconcentrated Cd was analyzed with Kelvin probe force microscopy and energy dispersive X-ray spectroscopy while observing the morphology change with an atomic force microscope and a scanning electron microscope. The preconcentrated Cd on the ECR nano-carbon electrode was revealed to be a thin sheet structure, which was significantly different from the Cd on a conventional carbon material that grows with a coralloid structure. The background current during an ASV measurement maintains a low level equivalent to that found with boron-doped diamond because the surface of the ECR nano-carbon is robust and angstrom-level flat. The carbon-electrode performance for ASV was improved by controlling its structure at a nanometer scale without any metal doping or coating. Finally, the ECR nano-carbon was used for biomolecular determination by electrochemical immunoassay with a CdSe nanoparticle label. Electrochemical immunoassay results were successfully obtained with the ECR nano-carbon, and they correlated well with fluorescence results obtained for CdSe nanoparticles.

High temperature electrochemistry of molten fluoride salt for measurement of dissolved chromium

An in situ electrochemical probe, utilising anodic stripping voltammetry (ASV), has been developed to measure dissolved Cr concentration in the molten salt LiF–KF–NaF (46·5–11·5–42 mol.-%), commonly referred to as FLiNaK. Tests were performed in a glassy carbon crucible in an argon atmosphere glovebox at a molten salt temperature of 650°C. Cyclic voltammetry was performed to determine reversibility and mid peak potential. The Cr2+/Cr0 reaction occurred with a mid peak potential of −0·51 V versus a 10 mol.-% Ni2+/Ni0 reference electrode. The integrated current from the anodic waves at this potential were used for Cr cation quantification. The integrated current from the ASV measurements correlated linearly with Cr concentration, measured independently using neutron activation analysis, over a range of 30–950 ppm (1·2–38 mmol L−1). This study is significant for determining Cr concentrations in high temperature molten FLiNaK salts exposed to Cr containing structural materials.

Highly Sensitive Detection of Cd2+ Using Boron Doped Diamond Electrodes

The electrochemical detection of Cd2+ has been performed by anodic stripping voltammetry on boron doped diamond (BDD) electrodes. A new technique is proposed, which involves adding a known amount of copper to the sample to deposit an amalgam of Cd-Cu on the surface of the BDD electrode. This amalgam is then stripped during voltammetry measurements, allowing the generation of highly accurate calibration curves for Cd detection (r2 = 0.99) with a lower detection limit of 10 ppb. The conditions that are used for the anodic stripping voltammetry measurements have been optimized to avoid the deposition of cadmium and the appearance of the stripping peak related to copper. Real samples could contain a certain amount of copper, so the influence of small variations of Cu2+ concentration has been investigated and it was found that such variations have no influence on the accuracy of the calibration curve for Cd detection. The influence of other metals that could be dissolved in the sample has also been studied, and it was shown that lead and selenium have a negative influence on the technique. However, this negative interference can be eliminated by increasing the concentration of copper that is introduced in the sample. Furthermore, other species such as boron or chromium have no influence on the anodic stripping voltammetry measurements, so accurate calibration curves for Cd determination could be constructed in the presence of Pb, Se, B and Cr.

Pb uptake by the marine mussel Mytilus sp. Interactions with dissolved organic matter

It is well known that dissolved organic matter binds metal ions and buffers them in natural waters. Although it is believed that a decrease in metal ion concentration should lead to a decrease in metal bioavailability, previous work has shown that Pb uptake by Mytilus edulis gills is greatly enhanced in the presence of humic acids. In the present work, the effect of more soluble organic matter (fulvic acids and DOM extracted from river) on Pb uptake by mussels and their gills is studied. Pb complexation by these organic substances was measured by anodic stripping voltammetry (ASV) and it is proven that Pb uptake by mussel gills in the presence of fulvic acids can be successfully predicted according to ASV-labile Pb concentrations. However, Pb uptake by whole mussels in the presence of river DOM is slightly higher than predicted on the basis of ASV measurements. The possible reasons leading to different effects of DOM on Pb uptake by mussels are discussed according to physicochemical properties of DOM.