Electrochemical properties of photocurable membranes for all-solid-state chemical sensors

The development of ion-selective electrodes with inner solid contact is described using photocurable acrylated polyurethane matrices and electron-ion exchanger (EI), which provides a reversible transition from electrical conductivity in the metal to ionic conductivity in the membrane phase. The application of a photocurable polymer matrix gives the possibility to use modern photolithographic techniques for the formation of all-solid-state chemical sensors. The influence of the polymer matrix and of the preparation of the membrane on the electro-chemical properties of calcium-selective membrane sensors is shown. For carbonate-selective membranes the possibility of improvement of electrochemical characteristics by incorporation of the anionic additive tetrakis (4-chlorophenyl) borate was studied. Received: 14 June 1997 / Revised: 23 September 1997 / Accepted: 9 October 1997     

A solid-state ion-selective electrode with an ionic-electronic transducer for determining chlordiazepoxide

A solid-state ion-selective electrode for determining chlordiazepoxide is described. A characteristic feature of the electrode is the presence of an intermediate conducting polymeric layer (transducer) of poly(o-aminophenol) between the ion-selective membrane with ionic conduction and a Pt conductor. The properties of ion-selective electrodes with transducers are compared with those of ISEs without transducers (coated-wire electrodes, CWEs). The most important distinctive features of ion-selective electrodes with transducers are the high stability of their potentials in time and their small sizes. The main performance characteristics of the electrode and the scope of its application are found.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 74–78.Original Russian Text Copyright © 2005 by Gorelov, Ryasenskii, Kartamyshev, Fedorova.     

Neutral-carrier-type potassium ion-selective electrodes based on polymer-supported liquid-crystal membranes for practical use.

Polymer-supported liquid-crystal membranes have been designed for neutral-carrier-type potassium ion-selective electrodes, aiming for practical applications of high-performance liquid-crystalline membrane ion sensors. Two types of polymer-supported liquid-crystal membranes were tested for their usefulness; one is microporous poly(tetra fluoroethylene) (PTFE) membranes impregnated by thermotropic liquid-crystalline compounds, and another is poly(methyl methacrylate) (PMMA) membrane dispersing the same liquid-crystalline compounds. Both of the polymer-supported liquid-crystal membranes containing a liquid-crystalline benzo-15-crown-5 neutral carrier as well as a lipophilic anion excluder work well as ion-sensing membranes for potassium ion-selective electrodes, the ion selectivities of which can be switched by the measurement temperatures. Specifically, PTFE-impregnated liquid-crystal membranes are better than the PMMA-dispersed ones in the sensitivity and selectivity of the resulting ion electrodes. A potassium ion assay in blood sera has proved that neutral-carrier-type ion-selective electrodes based on the polymer-supported liquid-crystal membranes are reliable for practical uses.     

Kinetic considerations of ion selectivity coefficients of ion-selective electrodes based on neutral carriers

Ion selectivity coefficients of ion-selective electrodes based on neutral carriers are described by means of a mixed potential model of ion transport reactions at the aqueous solution/ion-sensitive membrane interface. The decrease in ion selectivity can be explained by the deviations from the equilibrium conditions, which arise from the ionic partial current across the interface, but the proposed correspondence of the exchange current density of ion transfer reactions with the ion selectivity coefficients is rationalized only for certain conditions of the kinetic parameters. The ion selectivity for liquid membrane transport is discussed starting from three different rate-determining steps. It is shown that the potentiometric selectivities of ion-selective electrodes and the transport selectivities are correlated when the ionic transfer across the aqueous solution/ membrane interface is fast compared with the complex ion transport through the membrane. The significance of a kinetic approach for the design of neutral carriers for ion-selective electrodes is stressed.     

Studies on the Preparation and Analytical Applications of Various Metal Ion-Selective Membrane Electrodes Based on Polymeric,Inorganic and Composite Materials—A Review

Ion-selective membrane electrodes commonly known as electrochemical sensors are important in view of the ability to make direct or indirect measurement of various metal ions. The fact is that the use of ion-selective electrodes for such type of measurements requires relatively inexpensive equipment, which makes ion-selective electrodes attractive to scientists in many disciplines. Thus, potentometric sensors can offer an inexpensive and convenient method for the analysis of heavy metal ions in solutions providing acceptable sensitivity and selectivity. For this purpose, many organic, inorganic, chelating, intercalating and composite materials were studied as electroactive materials for the preparation of ion-selective membrane electrodes. The present study provides a detailed review of literature for the fabrication, characterization and analytical applications of ion-selective membrane electrode based on different electro active components.     

Zeta potential of dodecyltrimethylammonium hydroxide micelles in water

 The electrophoretical mobility of dodecyltrimethyl-ammonium hydroxide micelles has been measured at two different concentrations giving values similar to that determined in other surfac-tants. There is a good agreement between micelle ionization degrees computed from zeta potential measurements and those from ion-selective electrodes experiments. This demonstrates that electrophoresis experiments may be replaced by the simpler ion-selective electrode measurements to determine micelle surface potential. It has also been concluded that ion-selective electrodes detect only the non-micellised ions, that only free ions contribute to the intermicellar solution ionic strength, and micelles do not affect the result, and that the dependence of the electrophoretic mobility on the soap concentration is due to the reduction of the micelle net charge when the ionic strength of the intermicellar solution arises. Received: 2 December 1996 Accepted: 24 February 1997     

Adding Plasticizer Dispersible Conducting Polymer to the Ion-selective Membrane Composition – Revitalizing Single Piece Ion-selective Electrodes Concept

Typically, ion-selective electrodes used in current triggered electrochemical sensing apply a conducting polymer layer covered with an ion-selective membrane. In this work we propose an ion-selective membrane containing a dispersed conducting polymer. Thus obtained system allows elimination of the Achilles hell of heterogeneous ion-selective membranes containing solid particulates dispersed within the ion-selective polymeric membrane. The herein proposed system, even for high conducting polymer loading equal to 5 % w/w, is characterized with insensitivity towards redox interferences, as well as potentiometric detection limits, selectivity well comparable with that for other ion-selective electrodes constructions. Under voltammetric conditions, with increasing loading of the conducting polymer in the membrane cathodic peak potentials are shifted towards more negative values, yet the linear dependence of the peak potential on logarithm of concentration of the analyte in the solution is preserved.     

Determination of a polymer surfactant by potentiometry with an ion-selective electrode using inorganic or organic anions as counterions of the electrode-active compound

Ion-selective electrodes for the determination of a cationic polymer surfactant with membranes containing ion pairs of polysulfonylpiperidinylmethylene hydroxide (PSPMH) with inorganic complex anions or organic counterions of the azo dye series as the electrode-active compound are described. Electrochemical characteristics and analytical potentialities of film ion-selective electrodes based on ion pairs PSPMH-potassium tetraiodomercurate, PSPMH-Magneson IREA, and PSPMH-Stilbazo R are compared. The influence of the concentration of the electrode-active compound in the membrane, the pH and ionic strength of the PSPMH solution, the lifetime of the membrane, and the number of measurements on the characteristics of ion-selective electrodes is studied. A procedure is developed for the potentiometric determination of PSPMH in aqueous solutions using proposed ion-selective electrodes. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

因子效应函数的正交多项式展开优化离子电极的膜组成

本文应用因子效应函数的正交多项式展开数学方法,处理了两种电极的正交试验数据,导出电极斜率和电极膜的各组份含量的定量关系式,并用求导的方法求得电极的最佳膜组成。该法适用于探求电极响应参量与膜组成之间的定量关系并进行膜组成的优化。     

From extraction to ionometry

On the basis of existent data we have carried out a comparative analysis of equilibriums of formation and distribution of metal complexes in extraction and ionometry with liquid and plasticized ion-selective electrodes. We have shown that electrode-active compounds are practically identical to compounds formed via extraction, and hence common behavioural patterns and clas-sification of ionometric systems correspond to the patterns found in extraction systems. Distribution processes, which take place in the ion-sensitive membrane, may be considered as being common for bi-phase systems, primarily extrationary, whereby reactions of formation and distribution take place. This approach provides well-grounded explanation for an array of experimentally de-termined facts: for instance association between sensitivity and selectivity of ion-selective electrodes and resistance of complexes, utilized as electrode-active compounds; hydrophobicity of complex and ligands; as well as the nature of the membrane dissolving agent.     

Ion-Selective Electrode for the Determination of Sulfadimezine

The main electroanalytical properties of ion-selective electrodes for determining sulfadimezine were studied. Quaternary ammonium salts containing different functional substituents were tested as ionophore groups in ion exchangers. The association constants of ionophores in membrane media, solubility products, and partition coefficients in the aqueous solution–membrane solvent system were calculated.     

Comparison of copper(II) ion-selective electrodes for measurements at micromolar concentrations

Four types of copper ion-selective electrodes have been tested for determining copper at concentrations below lO^-6 mol 1^l-1. None of the electrodes has a Nemstian response in dilute copper solutions in this concentration range, though their responses are linear in pCu buffer solutions. The causes of the deviations are a direct redox effect in the case of an electrode with a Cu_1.8,Se single crystal membrane, production of copper ions by oxidation of the membrane itself in Ag₂S—CuS membrane electrodes, and a combination of the two in the case of the R??i?ka Selectrode. The electrode potentials are affected by the oxygen content and pH of the sample solution and the condition of the membrane surface. Precision tests on two types of electrode are described.     

Sulfonamides as Ionophores for Ise. III. Guanidinium Ion-Selective Electrodes Based on Lipophilic Bis-Sulfonamide Podands

Abstract

PVC membrane ion-selective electrodes based on bis-sulfonamide podands and DOS (Bis(2-ethylhexyl)-sebacate) as plasticizer are described. They were found to behave as guanidinium ion sensors, exhibiting high selectivity for guanidinium ions over potassium ions.     

Rapid determination of lithium in serum samples by capillary electrophoresis

Lithium salts are still one of the most popular therapeutic approaches to the treatment of bipolar disorders, notwithstanding the introduction of more modern, less toxic drugs. Because of a narrow therapeutic range, lithium serum concentrations must be strictly monitored during the treatment to avoid life-threatening neurotoxicity. For this purpose, methods based on flame photometry or ion-selective electrodes are usually applied. The aim of the present work was to develop and validate a simple method for the determination of lithium in serum based on capillary zone electrophoresis with indirect detection. A validation of the method was carried out, including a comparison with an automated routine method based on ion-selective electrodes.     

Quality control criteria for solid-contact, solvent polymeric membrane ion-selective electrodes

After a long history and conflicting views, solid-contact (SC) solvent polymeric membrane ion-selective electrodes (ISEs) emerged as reliable potentometric-sensing devices with unique advantages. From the large variety of proposed SCs inherently conductive polymers emerged as the materials of choice. In our view, the most attractive feature of SC ISEs is their compatibility with thin- and thick-film microfabrication technologies that can provide cheap, mass-produced sensors and sensor arrays that can be integrated with the measuring, data acquisition, and control electronics in a straightforward way. However, despite the impressive properties of certain SC electrodes and their potential advantages, they remained primarily in the research laboratories. To make the jump from the research laboratories into commercial devices, it would be essential to prove that miniaturized SC ISEs can indeed match or surpass the performance characteristics of the conventional, liquid-contact macroelectrodes. In addition, it would be important to settle on the quality control criteria and testing protocols for assessing the performance characteristics of SC electrodes. It could help in interpreting the sometimes-inconsistent experimental data. Once cheap, miniaturized, SC ISEs will mach the performance characteristics of macroscopic-size electrodes, it is expected to have an important impact in a variety of applications requiring robust, maintenance-free, or single-use ISEs, e.g., in homecare or bedside diagnostics, environmental analysis, and quality control assessment. In addition, reliable SC ISEs are expected to revitalize the field of ion-selective field effect transistors and open new possibilities in combination with nanowire-based devices.     

Ion-selective sensors for determining Au(CN)<Stack><Subscript>2</Subscript><Superscript>−</Superscript></Stack> with membranes based on the ionic liquid tetradecylphosphonium dicyanoaurate

A polymeric membrane for an ion-selective electrode is proposed on the basis of supramolecular systems including a polymeric compound (polyvinyl chloride, PVC) and an ionophore (ionic liquid tetradecylphosphonium dicyanoaurate) in which ionic liquid is simultaneously used as a PVC plasticizer. The selectivity, linear response range, and potential stability of ion-selective electrodes with the optimum membrane composition are measured. The detection limit for Au(I) with the developed electrode is 4.5 × 10^?7 M.     

Array of potentiometric sensors for simultaneous analysis of urea and potassium

Urea biosensors based on urease immobilized by crosslinking with BSA and glutharaldehyde coupled to ammonium ion-selective electrodes were included in arrays together with potassium, sodium and ammonium PVC membrane ion-selective electrodes. Multivariate calibration models based on PCR and PLS2 were built and tested for the simultaneous determination of urea and potassium. The results show that it is possible to obtain PCR and PLS2 calibration models for simultaneous determination of these two species, based on a very small set of calibration samples (nine samples). Coupling of biosensors with ion-selective electrodes in arrays of sensors raises a few problems related to the limited stability of response and unidirectional cross-talk of the biosensors, and this matter was also subjected to investigation in this work. Up to three identical urea biosensors were included in the arrays, and the data analysis procedure allowed the assessment of the relative performance of the sensors. The results show that at least two urea biosensors should be included in the array to improve urea determination. The prediction errors of the concentration of urea and potassium in the blood serum samples analyzed with this array and a PLS2 calibration model, based on nine calibration samples, were lower than 10 and 5%, respectively.     

Ion-selective electrodes – istory and conclusions

 The working mechanism of ion-selective electrodes has been investigated. The contradictions of theories deduced from so-called analogous phenomena are discussed in detail. Based on experiments made by the author’s research group the conclusion was drawn that only the surface (the active groups located there) takes part in the potential-determining reaction and the bulk resistance of the membrane plays a role only in the selection of the instrument used for potential measurement. Received: 15 May 1995/Revised: 12 August 1995/Accepted: 11 August 1995     

Ion-selective electrodes – istory and conclusions

 The working mechanism of ion-selective electrodes has been investigated. The contradictions of theories deduced from so-called analogous phenomena are discussed in detail. Based on experiments made by the author’s research group the conclusion was drawn that only the surface (the active groups located there) takes part in the potential-determining reaction and the bulk resistance of the membrane plays a role only in the selection of the instrument used for potential measurement. Received: 15 May 1995/Revised: 12 August 1995/Accepted: 11 August 1995