Determination of Lead(II) Using Screen‐Printed Bismuth‐Antimony Film Electrode

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

Sensitive Stripping Determination of Cadmium(II) and Lead(II) on Disposable Graphene Modified Screen‐Printed Electrode

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

Chalcogenide based all-solid-state thin electroplated ion-selective membrane for Hg(II) flow-injection determinations

The response to Hg(II) of a thin all-solid-state Te-doped silver chalcogenide membrane, described by the general formula Ag₂ + δSe_{1 − x}Te_x, which has been electrochemically prepared following a previously proposed approach, has been investigated. The kinetics of formation of the membrane's secondary dynamic response to Hg(II) has been successfully combined with the precise timing and transient signal, typical for flow-injection (FI) measurements, in developing a sensitive and reliable mercury FI detector. Under optimized stream conditions it exhibits a linear Nernstian response, with a double slope of the calibration graph of 59 mV dec⁻¹, over the mercury(II) concentration range 10⁻⁶ − 10⁻³ M, the typical sample throughput amounting to about 70 samples per hour. The observed chemical amplification of the signal is due to the specificity of the processes dominating the initial step in formation of the steady-state signal of the membrane to mercury. The analytical performance of the Hg(II) FI detector, as regards sensitivity, reproducibility, selectivity and long-term stability has been thoroughly investigated. The exact procedure for membrane electrodeposition is given and the potential of the proposed approach as a cost-effective way for preparing chalcogenides of unique structure and properties has been outlined in the above context.     

PVC‐Based Ion‐Selective Electrodes with Enhanced Biocompatibility by Surface Modification with “Click” Chemistry

We report here on plasticized ion‐selective poly(vinyl chloride) membranes with increased biocompatibility by means of a copper(I)‐catalyzed azide‐alkyne cycloaddition (‘click chemistry’) on the surface of finished membranes. We aimed for increasing the hydrophilicity of the surface and the application of NO releasing molecules. Employing the first principle, sodium selective membranes based on azide‐substituted PVC were modified with different length poly(ethylene glycol) (PEG) chains. For the second, cysteine groups were used as a nitrous oxide releasing substance. Surface modification was confirmed by Electrochemical Impedance Spectroscopy (EIS). Potentiometric measurements in undiluted whole blood showed an increased sensor stability in comparison to unmodified PVC. Membrane surfaces after 18 h contact with blood were analyzed with Scanning Electron Microscopy (SEM) and revealed a reduced level of blood cell adsorption on membranes modified with tetraethylene glycol (TEG) and PEGs. In contrast, cysteine modified membranes did not exhibit improved fouling resistance, suggesting that nitric oxide release by itself is not a sufficiently efficient mechanism.     

Electrocatalytic Oxidation of Amines on a Mediator‐Modified Electrode by Electrochemical Copolymerization of Nitroxyl Radical Precursor Containing Pyrrole Side Chain and Bithiophene

This paper describes the electrocatalytic oxidation of amines on TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl)‐modified electrodes prepared by electrochemical copolymerization of TEMPO precursor containing pyrrole side chain and 2,2′‐bithiophene. The modified electrode exhibits electrocatalytic activity for the oxidation of primary and secondary amines. Cyclic voltammetric studies showed that the peak current of the cyclic voltammogram increased linearly with increasing concentration of amine in the sample solution.     

Electroactive Polymers: Developments of and Perspectives for Dielectric Elastomers

We present the development and applications of dielectric elastomers. For the last 10 years the significance of this class of polymers has risen as more applications seem possible and first products have been commercialized.     

A New Neutral Carrier for Silver Ions Based on a Bis(Thiothiazole) Derivative and its Evaluation in Membrane Electrodes

Membrane electrodes based on 2,2-dithiobis(benzothiazole), DTBBT, as a neutral carrier for silver ions are described. Silver-selective membrane electrodes formulated with 2wt% DTBBT ionophore and 50mol% TFPB in an FPNPE plasticized poly (vinyl chloride) exhibited near-Nernstian responses towards silver ions (60.3±0.5mVdecade^–1) over a wide silver ion activity range of 0.83µM to 94mM. Increasing the amount of anionic sites, TFPB, to 100 or 150mol% (relative to the DTBBT weight) resulted in super-Nernstian responses toward silver ions. Membrane electrodes prepared using a low dielectric constant plasticizer, however, exhibited sub-Nernstian responses. Polymer membrane electrodes with optimal composition (i.e., 2wt% DTBBT, 50mol% TFPB in FPNPE plasticized poly(vinyl chloride)) exhibited high potentiometric selectivity towards silver ions over alkali, alkaline earth, transition metal ions, as well as heavy metal ions such as Hg²⁺ and Pb²⁺. A good correlation was found between the potentiometric selectivity coefficients and the change in the UV-visible spectra of the ionophore upon exposure to different metal ions. The overall performance of the silver-selective membrane electrodes based on DTBBT ionophore, which is available at low cost, was found to be comparable to the performance of silver electrodes prepared with Fluka silver ionophore-IV. A DTBBT-based silver electrode was used as an indicator electrode for titrations of silver ions using standard sodium chloride solutions. Sharp inflections occur at the end point, and the data obtained showed 99.4% recovery with a standard deviation of 0.7% (n=3). In addition, the applicability of the DTBBT-based silver-selective electrode is illustrated by measuring the silver concentrations in natural water spiked with silver nitrate and by analyzing the silver in electroplating wastewater samples. The results obtained utilizing a DTBBT-based silver electrode showed very good agreement with the standard methods of analysis.     

Carbon paste electrodes: correlation between the electrochemical hydrogen storage capacity and the physicochemical properties of carbon blacks

The difficulties in the use of carbon paste electrodes to quantify the electrochemical adsorption of hydrogen in nanocarbon materials are described. Chronoamperometry studies using a Ferro/Ferri redox couple were performed to obtain the electrochemical active area of paste electrodes prepared by dispersion of differing samples of carbon blacks (CB) within silicon oil. This electrochemical active area was combined with the BET-surface area of the carbon blacks, to obtain the mass of superficial carbon involved in the electrochemical processes. To assure equal conditions for comparison, the electronic conductivity of the paste was equivalent in all the samples. From our results it appears that cyclic voltammetry, combined with carbon paste electrodes and nitrogen adsorption isotherms, provides a simple and less expensive route for the qualitative evaluation of the electrochemical hydrogen uptake of novel carbon materials. Still, for quantitative measurements, some issues remain unsolved in highly structured carbons, where the lack of penetration of the bulky Ferro/Ferri redox couple in the micropores of the CB and the occurrence of solid-state diffusion cause the underestimation of the mass involved in hydrogen adsorption.     

Transport properties and electroanalytical response characteristics of drotaverine ion-selective sensors

The construction and electroanalytical response characteristics of poly(vinyl chloride) matrix ion-selective sensors (ISSs) for drotaverine hydrochloride are described. The membranes incorporate ion-association complexes of drotaverine with tetraphenylborate, picrate, tetraiodomercurate, tetraiodobismuthate, Reinecke salt, and heteropolycompounds of Keggin structure—molybdophosphoric acid, tungstophosphoric acid, molybdosiliconic acid and tungstosiliconic acid as electroactive materials for ionometric sensor controls. These ISSs have a linear response to drotaverine hydrochloride over the range 8×10^–6 to 5×10^–2 mol L^–1 with cationic slopes from 51 to 58 mV per concentration decade. These ISSs have a fast response time (up to 1 min), a low determination limit (down to 4.3×10^–6 mol L^–1), good stability (3–5 weeks), and reasonable selectivity. Permeabilities and ion fluxes through a membrane were calculated for major and interfering ions. Dependences of the transport properties of the membranes on the concentrations of the ion exchanger and near-membrane solution and their electrochemical characteristics are presented. The ISSs were used for direct potentiometry and potentiometric titration (sodium tetraphenylborate) of drotaverine hydrochloride. Results with mean accuracy of 99.1±1.0% of nominal were obtained which corresponded well to data obtained by use of high-performance liquid chromatography.