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The emergence of elevated concentrations of bromate, classified as a 2B type carcinogen, in drinking water following the treatment of water supplies with ozonation and other oxidation methods has underscored the importance of developing methods for reliable and rapid screening of drinking water. In this work, we report the use of electro activated riboflavin (RF) impregnated Ketjen black (KB) modified screen-printed electrode (el RF@KB-SPE) for the determination of bromate. The sensing surfaces were subjected to morphological and structural characterization using scanning electron microscopy and Raman spectroscopy. These analyses confirmed the successful modification of the electrode with an extended el RF@KB porous coating. Based on cyclic voltammetry (CV) and electrochemical impedance spectroscopy measurements, the response of el RF@KB-SPE towards bromate can be described through a dual mechanism involving i) an autocatalytic chemical/electrochemical process that predominantly occurs in the finite length pores of KB, and ii) an RF-mediated electrocatalytic process. Notably, the data demonstrated that the advanced electrocatalytic properties of the otherwise electrocatalytically inactive absorbed RF molecules are endowed after a simple electro activation process (three CV scans). Amperometric measurements at −0.05 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of bromates over the concentration range 0.50−18.0 μM, achieving a limit of detection (3 σ /slope) of 0.04 μM. The interference effect of various electroactive species was investigated demonstrating that el RF@KB-SPE is highly selective to bromate. The analytical utility of the method was evaluated in spiked tap water samples. Recoveries were 91.2 − 106.4 %. [Display omitted] • Bromate sensing in electroactivated riboflavin impregnated carbon black (KB) SPE. • CV and EIS data support a dual autocatalytic redox mediation mechanism. • Electrocatalysis occurs in a finite-length diffusion regime within the pores of KB. • Impregnation of riboflavin in KB porous promotes the electroanalysis of bromate. • Data demonstrated high selectivity and analytical utility in water samples. [ABSTRACT FROM AUTHOR]

We report a simple method for the preparation of a stabilized palladium nanoparticle-polyaniline composite by mixing aniline and PdCl 4 2 − in aqueous acidic solutions. Pd nanoparticles (Pd NP) were produced by subsequent reduction of the pre-organized material with different concentrations of NaBH 4 . Under optimum conditions (0.1 M NaBH 4 in ethanol for 1 h at 0 °C), Pd NP with a size of 5–10 nm were obtained, as revealed by transmission electron microscopy. The so-formed pre-organized material was also characterized with scanning electron microscopy, X-ray diffraction, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry, nuclear magnetic resonance spectroscopy, and cyclic voltammetry. The developed catalyst exhibited a large electrochemically active surface area (25.2 m 2 g −1 catalyst) and remarkable mass activities for the electro-oxidation of methanol (602 A g −1 Pd) and ethanol (433 A g −1 Pd) in alkaline media. The excellent electrocatalytic performance of the developed polyaniline-Pd NP composite material renders it as a promising anode catalyst in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

• Liquid exfoliated Sbene nanosheets and electrochemical passivation of Sbene/SPE. • Cathodic measurements with passivated Sbene/SPE in non-deoxygenated solutions. • In-situ preparation of Sbene oxide/PEDOT:PSS nanocomposite via tip sonication. • Advanced detection capabilities of Sbene oxide/PEDOT:PSS/SPE to 4-NT in real samples. Herein, we present the production of antimonene nanosheets and the in-situ preparation of antimonene oxide/PEDOT:PSS nanocomposite via tip sonication of bulk β-phase antimony in water and aqueous PEDOT:PSS, respectively. Nanomaterials were characterized via SEM, EDX, XRD, FT-IR, electrochemical impedance spectroscopy and cyclic voltammetry, while the resulting modified graphite screen-printed electrodes (Sbene/SPE and Sbene oxide/PEDOT:PSS/SPE, respectively) were evaluated in the cathodic determination of 4-nitrotoluene (4-NT), which was used as a model compound, in the presence of dissolved oxygen and in deoxygenated environments. Data document the electrochemical passivation of Sbene/SPE, which, on the one hand, demonstrate a beneficial poor activity towards the oxygen reduction reaction, and on the other hand, enhanced detection capabilities, thus allowing the determination of 4-NT at the micromolar concentration level at non-deoxygenated solutions. As a result, passivated Sbene/SPE show great promise in sensing applications outside of the laboratory where the deoxygenation of the samples is a big obstacle. Moreover, data demonstrate enhanced detection capabilities for Nafion membrane protected Sbene oxide/PEDOT:PSS/SPE, in deoxygenated solutions, which exhibit a detection range from 50 to 5000 nM 4-NT, while achieving an LOD of 16.7 nM (S/N 3). Nafion membrane is essential for the reusability of the electrodes. Sbene oxide/PEDOT:PSS/SPE was also used to the analysis of a spiked river water sample. Recovery was 97.9%. [ABSTRACT FROM AUTHOR]

Abstract: This review outlines the theoretical background of impedimetric biosensors and presents different types of impedimetric immunosensors along with the instrumental approaches that have been so far proposed in the literature for the evaluation of their performance. The electrode assemblies have been classified in four main categories with respect to the electrode material, the type of the insulating layer and the immobilization platform that have been used for their construction. Additionally, some selected works on recent developments in immunosensors, which are based on polymer degradation phenomena, magnetic nanobeads, etc. as well as strategies for the amplification of the measuring signals, are also presented. [Copyright &y& Elsevier]

Abstract: Investigation of metal can discoloration, lacquer adhesion failure and side seam steel corrosion in tin plated cans containing cooked octopus in brine was evaluated with X-ray microanalysis (energy dispersive X-ray spectroscopy, EDS) and electrochemical impedance spectroscopy (EIS). The effectiveness of EDS to analyze corrosion defects in metal food containers has been proven already in previous studies carried out in our laboratory. Complementary and/or alternative to sophisticated surface analysis methods, which require advanced and expensive instrumentation, simple and inexpensive quality tests based on EIS were also performed and results are discussed. Obvious alterations of the electrochemical properties of corroded and non-corroded samples (internal can walls and side seam) used as working electrodes in a common three-electrode compartment electrochemical cell can be used for rapid and simple evaluation of corrosion defects in tinplated food cans. [Copyright &y& Elsevier]

Abstract: Scanning electron microscopy (SEM) and X-ray microanalysis (EDS) were used to investigate metal can discoloration and lacquer adhesion failure in enameled food cans containing tuna in vegetable oil and octopus in brine, respectively. Black and brown spots on the internal surface of the can body were caused by the formation of FeS and SnS, respectively. The source of metal can discoloration was traced to inadequate lacquering of the tin plated steel, exposing both tin and iron to sulfur containing amino acids originating from the tuna product. Enamel adhesion failure in canned octopus was also traced to local defects in the lacquer coating enabling both NaCl and citric acid contained in the brine to cause enamel blisters on the can body leading to lacquer peeling and in turn to local detinning and steel corrosion. The first defect known as “sulfide staining” is harmless to human health and does not usually affect the product. The second defect may cause extensive detinning and steel corrosion possibly affecting the safety of the canned product. This postulation is supported by iron and tin concentrations both in the product and liquid medium carried out by atomic absorption spectroscopy. [Copyright &y& Elsevier]

Abstract: Titanium dioxide films were anodically formed at various potentials up to 65V in 1M H2SO4. Oxide films were characterized by performing various techniques, including electrochemical impedance spectroscopy, scanning electron microscopy, Raman spectroscopy, ellipsometry and diffuse reflectance FT-IR spectroscopy. Low voltage anodization (up to 10V) results to amorphous TiO2, whereas at higher applied potentials (up to 65V), anatase is the predominant form. Anatase films were further hydroxylated with an acidic agent and the effect of this treatment on the overall impedance of the electrodes was studied with impedance spectroscopy. The potential use of anodic (anatase) Ti/TiO2 electrodes in the development of impedimetric immunosensors is also demonstrated by monitoring the immunoreaction of avidin/anti-avidin with different instrumental approaches based on a FRA analyzer, an LCR-meter and a home-built charge integrator (Multipulser). [Copyright &y& Elsevier]

Abstract: The design and development of a palm-sized (9cm×11cm×3cm), cost-effective, microcontroller-operated analyzer for direct amperometric measurements is described. The low-power-consumption electronics used allow 8h of autonomous operation with a 9V battery (110mAh), making thus this unit suitable for in-field measurements. Its operation is based mainly on the simple two-electrode potentiostatic mode, although the three-electrode mode is an option. The use of a microcontroller combined with analog and digital supporting circuits allows: (i) generation of the applied potential and the acquisition of analog signals with a gain auto-scaling capability; (ii) interaction with the operator for setting the measurement parameters; (iii) processing of data and displaying result on an LCD screen. Numerical data are automatically stored in memory and they can be retrieved by a personal computer through an RS232 port, either for creating measurements archives or for advanced processing. For this purpose, a program has been developed (on the LabVIEW platform) to provide a user-friendly graphical interface. The utility of this amperometric analyzer was assessed by performing experiments for the determination of ascorbic acid in standard solutions and pharmaceutical tablets. [Copyright &y& Elsevier]

An enzymatic method for the individual or simultaneous determination of pyruvic acid and acetaldehyde is described. Alcohol dehydrogenase (ADH) was immobilized onto aminopropyl-modified controlled pore glass, which was then used for the construction of packed-bed (PB) reactors. ADH catalyses the reduction of acetaldehyde to ethanol, in the presence of the coenzyme NADH, which is oxidized to NAD+. Photometric measurements in a fully automated flow injection (FI) manifold are used to monitor the decrease of NADH absorbance at 340 nm. The possibility of pyruvate measurements, by combining the above mentioned system with soluble pyruvate decarboxylase (PyDC) is also demonstrated. PyDC catalyses the decarboxylation of pyruvate to acetaldehyde. Analytical parameters such as the buffering system, working pH, flow rate, sample size, and NADH concentration were studied. The interference of various compounds present in real samples was also investigated. Linear calibration graphs over the ranges 0.08–1.25 and 0.04–0.4 mM acetaldehyde were constructed in the presence of 50 mM succinate pH 7.5 and 50 mM phosphate pH 7.0 buffering systems, respectively. A linear calibration graph over the range 0.08–1.25 mM pyruvate was also constructed in the presence of 50 mM succinate pH 7.5 buffer solution. The reactors remain active for more than 6 months under specified storage conditions. The maximal sample throughput is 30 h−1 and the R.S.D. of the method is 0.9% for 0.2 mM acetaldehyde (n=6). The suitability of the proposed method for real samples was tested by recovery studies. [Copyright &y& Elsevier]

A concentric thin layer cell accommodating a non-standard 0.2 mm diameter pencil graphite disposable working electrode is described. The cell was installed into HPLC manifold as an electrochemical detector. Trouble-free operation in mobile phases containing both low and high content of organic solvents is demonstrated by HPLC analyses of phenolic acids and tocopherol isomers. The data obtained from HPLC separation of model mixtures of gentisic, caffeic and dihydrocaffeic acids show a remarkable electrolytic efficiency exceeding 80% at 200, and 50% at 500 μL min−1, while for gentisic acid the limit of detection (LOD) was 0.4 nmol L−1 at 20 microliter sample loading (8 fmol on-column). Similar performances were found in non-aqueous mobile phase, where a LOD of 0.8 nmol L−1 was achieved for delta-tocopherol. The developed flow-through detector is designed to allow easy replacement of pencil graphite working electrode in a highly reproducible manner. The relative standard deviation for the HPLC analysis of tocopherol isomers was of 5.3% (n = 3, C = 500 nmol L−1). The combination of simple construction, excellent electrochemical performance and hydrodynamics identical to that of commercial UV-VIS HPLC detector suggests that the proposed device is a viable low-cost alternative to commercially available electrochemical detectors. [ABSTRACT FROM AUTHOR]

This work reports on a new bipolar electrochemistry based device for the detection of reducing compounds that are oxidized at the anode compartment of a “closed” bipolar electrode cell by recording the onset driving voltage at which an electrodeposited metal track, being visible by the unaided eye, is formed at the cathode pole. The concept is demonstrated for the determination of ascorbic acid and hydrogen peroxide by using an acidic solution of copper(II) chloride, while the underlying theory is explained. The onset driving voltage of the indication event (formation of the metal track) is found to be dependent on the concentration of the targets. Compared with the existing bipolar electrochemistry based analytical methods, the proposed method: i) introduces for the first time the onset driving potential as a measure of the target concentration, and ii) does not require extra instrumentation or devices for measuring the reporting event (intensity of emitted light, fluorescence or electrode’s length at the sub mm level). Along with its inherent advantages of low cost and simplicity it paves the way for the development of low-cost, portable analytical devices for reducing species and, potentially, for the development of biosensors based on oxidase enzymes. [ABSTRACT FROM AUTHOR]