Coated-wire ion-selective electrodes

Coated-wire ion-selective electrodes were first developed in 1971, and comprise a film of polyvinyl chloride or other suitable polymeric matrix substrate containing a dissolved electroactive species, coated on a conducting substrate (generally a metal, although any material with conductivity substantially higher than that of the film can be used). Electrodes of this sort are simple, inexpensive, durable and capable of reliable response in the concentration range of 10^?1 to 10^?6 M for a wide variety of both organic and inorganic cations and anions. The principles on which these electrodes are based, as well as their application to a variety of analytical problems, will be discussed.     

Screen-printed copper ion-selective electrodes

A simple, low-cost and reproducible method for the mass production of potentiometric ion-selective electrodes for copper ions is presented. These planar, strip sensors were obtained by screen-printing. The application of pastes cured at low temperature allows printing of the sensors on low-cost, plastic substrates. The pastes for printing of ion-sensitive thick-film membranes were based on copper (1) and copper (II) sulfides. The analytical characteristics of the thick-film electrodes were compared. The analytical properties (range of determination, sensitivity, selectivity, response time) of the copper (I) sulfide-based sensors were comparable with those for conventional ion-selective electrodes.     

Screen-printed copper ion-selective electrodes

A simple, low-cost and reproducible method for the mass production of potentiometric ion-selective electrodes for copper ions is presented. These planar, strip sensors were obtained by screen-printing. The application of pastes cured at low temperature allows printing of the sensors on low-cost, plastic substrates. The pastes for printing of ion-sensitive thick-film membranes were based on copper (I) and copper (II) sulfides. The analytical characteristics of the thick-film electrodes were compared. The analytical properties (range of determination, sensitivity, selectivity, response time) of the copper (I) sulfide-based sensors were comparable with those for conventional ion-selective electrodes. Received: 12 January 2000 / Revised: 13 March 2000 / Accepted: 16 March 2000     

Current trends in ion-selective electrodes

Recent advances in the development of ion-selective electrodes have led to the production of new potentiometric sensors with superb selectivity. These electrodes are frequently good enough to allow for analyses in complex, multicomponent samples such as blood or urine.     

Solvent polymeric membrane ion-selective electrodes

The significant role of poly(vinyl chloride) as a support polymer in solvent polymeric ion-selective electrodes is briefly reviewed. This lays emphasis on the way PVC has contributed to the relatively high state of development of conventional ion-selective electrodes, microelectrodes, coated-wire electrodes and ion-sensitive field effect transistors based on liquid ion-exchanger and neutral carrier ionophore sensors. Also discussed are possibilities of using alternative polymer matrices for overcoming some of the shortfalls of the PVC electrodes.     

Properties of naproxen ion-selective electrodes

Naproxen membrane electrodes based on different plasticizers and the quaternary ammonium salts (QASs) dimethyldidecylammonium bromide, methyltrioctylammonium chloride, or tetraoctylammonium chloride, were prepared. The following basic parameters were investigated for the optimal electrode: measurement range (10⁻⁴ − 10⁻¹ mol L⁻¹), slope of the linear range of the calibration curve (−58.3 mV decade⁻¹), limit of detection (6.0 × 10⁻⁵ mol L⁻¹), lifetime (2.5 months), dependence of the electrode potential on pH (5.5 − 9.0), reproducibility of potential (1.2 mV) and selectivity coefficients in relation to selected organic and inorganic anions. The electrode was utilized for determination of naproxen in tablets by the calibration curve method and the standard addition method.      

Bio-sensors based on ion-selective electrodes

Summary A review is given on bio-sensors based on ion-selective electrodes. By means of several examples of enzyme electrodes the salient features and the operating principles of the new sensors are illustrated. 72 literature references.

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Biosensoren auf der Grundlage von ionenselektiven Elektroden

Zusammenfassung Ein Überblick über Biosensoren wird gegeben. An Hand mehrerer Beispiele von Enzymelektroden werden die entscheidenden Eigenschaften und die prinzipielle Arbeitsweise dieser neuen Sensoren dargestellt. 72 Literaturzitate.

     

Linear titration plots with ion-selective electrodes

A computational method for simultaneous determination of the equivalence volume and the Nernstian slope of an ion-selective electrode is described. Treatment of data from linear titration and standard addition procedures is simplified by the use of equal additions of standard solution. Equivalence volumes and concentrations were determined with errors of 0.5-2% by the proposed method.     

Experience with mixed-salt ion-selective sulphate electrodes

Sulphate ion-selective electrodes with mixed-salt, pressed-pellet membranes have been manufactured and tested for response, stability and selectivity. Acceptable performance was obtained only with selected specimens. The addition of small amounts of cuprous sulphide to the membrane had no significant effect.     

Molecular design of calixarene-based ion-selective electrodes

In order to obtain insights into relationships between the calix[4]arene structure and the ion selectivity in the electrode system, 20 ionophoric calix[4]arenes were synthesized and their ion selectivity (with Na⁺ as a standard) estimated. Among these ionophoric calix[4]arenes, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-t-octylcalix[4]arene afforded the highest logK _NA,M ^pot value (–3.1) in the presence of 2-fluorophenyl-2-nitrophenylether (10) as the best of 13 plasticizers. This is the first example in which the Na⁺/K⁺ selectivity exceeds a factor of 10³ in the electrode system based on the neutral carrier. The high Na⁺ selectivity is attributed to modification of the upper rim which ostensibly has no relation with the component of the cavity. This paper demonstrates the potential relationships between the unique structure of the calix[4]arene-based ligands and selectivity performance for the design of ion-selective electrodes.     

Single-point potentiometric titrations with ion-selective electrodes

A single-point potentiometric titration method is described for the determination of silver(I), chloride and sulphate with ion-selective electrodes. Relative standard deviations in the range 0.1–1.25% can be obtained, depending on the quality of the electrodes used.     

Calixarene-based potentiometric ion-selective electrodes for silver

Four lipophilic sulphur and/or nitrogen containing calixarene derivatives have been tested as ionophores in Ag(I)-selective poly (vinyl chloride) membrane electrodes. All gave acceptable linear responses with one giving a response of 50 mV/dec in the Ag(I) ion activity range 10(-4)-10(-1)M and high selectivity towards other transition metals and sodium and potassium ions. This ionophore was also tested as a membrane coated glassy-carbon electrode where the sensitivity and selectivity of the conventional membrane electrode was found to be repeated. The latter electrode was then used in potentiometric titrations of halide ions with silver nitrate.     

Electrochemical studies on ion-selective polymer membrane electrodes

The selectivity and response of neutral carrier based polymer membrane electrodes are investigated via exchange current measurements for systems containing valinomycin, dibenzo-18-crown-6, and plasticizer alone in a polyvinyl chloride matrix. Using a transient galvanostatic step method, apparent exchange current densities of 1.3 X 10^?3 A/cm², 5.4 X 10^?6 A/cm², and 2.2 X 10^?9 A/cm² were obtained with K⁺ as the primary ion for the three types of membranes, respectively. Preliminary results indicate that the exchange current data obtained with this technique are complementary to the potentiometric response observed for the membranes studied.     

Application of ion-selective electrodes in flow analysis

Continuous flow techniques offer one of the most effective approaches to obtaining analytical data on a large scale and monitoring individual components in biological systems or in industrial effluents. The segmented flow methods developed by Skeggs¹ and the continuous flow methods, including liquid chromatography, which have been developed in the last 10 years are especially noteworthy.     

Potentiometric determination of penicillins with ion-selective electrodes

Quaternary ammonium, phosphonium and arsonium membrane electrodes sensitive to benzylpenicillin, ampicillin and oxacillin have been investigated. The order of merit of electrode performance is cetyltrioctylammonium> cetyltrioctylphosphonium> cetyltrioctylarsonium. The electrodes are suggested for use in rapid determination of penicillin drugs by direct potentiometry.     

Enhancing the blood compatibility of ion-selective electrodes

In vivo monitoring of various analytes is important for many bioanalytical and biomedical applications. The crucial challenge in this type of applications is the interaction of the sensor with the host environment, which is qualitatively described by the term biocompatibility. This review discusses recent advances in methods and materials used for the improvement of the biocompatibility of ion-selective electrodes especially as it relates to their interaction with blood components.