Application of nanoparticles in the potentiometric ion selective electrodes

Among the various analytical techniques available, the use of ion-selective electrodes is a wellestablished routine analytical technique. Good ion-selective electrodes (ISEs) possess many advantages over traditional methods for analysis and provide accurate, reproducible, fast, and regular selective determination of various ionic species. Modification of ISEs with nanoparticles has shown interesting ability toward various ions and biological molecules. In this article we review some of developments about applications of nanoparticles in the construction of ISEs in recent years.     

Theory and applications of ion-selective electrodes: Part 5

This review of ion-selective electrodes is arranged in the same way as earlier reviews in this series. The whole subject is steadily growing. More attention has been given to automatic methods of analysis with ion-selective electrodes, electrolysis at the interface of two immiscible electrolyte solutions, and to ion-selective field-effect transistors. The number of publications on traditional subjects like fluoride ion-selective electrodes has dropped. About 700 pagpers published between Spring 1981 and Spring 1983 are mentioned.     

A ladder conjugated polymer transducer for solid-contact Cu2+-selective electrodes

In recent years, there has been a pronounced interest in solid-contact ion-selective electrodes （SC-ISEs）, with emphasis on the use of conducting polymers as ion-to-electron transducer. In this work, a ladder conjugated polymer, thieno[3,2-b]thiophene （LCPT）, was investigated in fabricating Cu2＋-selective electrodes for the first time. The resulting electrodes were characterized by electrochemical impedance spectroscopy （EIS）, chronopotentiometry, and the water layer test. Results proved that the active LCPT facilitates the ion-to-electron transduction, and avoids the detrimental aqueous layer formed at the interface of SC-ISEs.     

Beyond potentiometry: robust electrochemical ion sensor concepts in view of remote chemical sensing

For about 100 years, potentiometry with ion-selective electrodes has been one of the dominating electroanalytical techniques. While great advances in terms of selective chemistries and materials have been achieved in recent years, the basic manner in which ion-selective membranes are used has not fundamentally changed. The potential readings are directly co-dependent on the potential at the reference electrode, which requires maintenance and for which very few accepted alternatives have been proposed. Fouling or clogging of the exposed electrode surfaces will lead to changes in the observed potential. At the same time, the Nernst equation predicts quite small potential changes, on the order of millivolts for concentration changes on the order of a factor two, making frequent recalibration, accurate temperature control and electrode maintenance key requirements of routine analytical measurements. While the relatively advanced selective materials developed for ion-selective sensors would be highly attractive for low power remote sensing application, one should consider solutions beyond classical potentiometry to make this technology practically feasible. This paper evaluates some recent examples that may be attractive solutions to the stated problems that face potentiometric measurements. These include high-amplitude sensing approaches, with sensitivities that are an order of magnitude larger than predicted by the Nernst equation; backside calibration potentiometry, where knowledge of the magnitude of the potential is irrelevant and the system is evaluated from the backside of the membrane; controlled current coulometry with ion-selective membranes, an attractive technique for calibration-free reagent delivery without the need for standards or volumetry; localized electrochemical titrations at ion-selective membranes, making it possible to design sensors that directly monitor parameters such as total acidity for which volumetric techniques were traditionally used; and controlled potential coulometry, where all ions of interest are selectively transferred into the ion-selective organic phase, forming a calibration-free technique that would be exquisitely suitable for remote sensing applications.     

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.     

The computational methods in the development of a novel multianalyte calibration technique for potentiometric integrated sensors systems

In recent years, integration and miniaturization of ion-selective electrodes (ISEs) have brought many benefits resulting in the possibility of simultaneous determination of the ions concentration in small volume samples. One of the key problems related to the preparation of potentiometric integrated sensors systems (PISSs) is a calibration procedure due to the necessity to calibrate each particular sensor separately. The main aim of the research was to develop a novel calibration method for PISSs fabricated with the use of an all-solid-state technology, which has been compared with other types of sensor calibration technique. The proposed algorithm concerns the method of calibration solutions composition determination for miniature ion-selective sensors before measuring in biological samples especially human saliva samples. This article also compares the parameters of ion-selective sensors for two types of PISSs, including ISEs based on gold (Au) and glassy carbon (GC) electrodes. In addition, a series of measurements was performed using PISS with Au-ISEs in samples of human saliva, which were preceded by different types of sensor calibration and compared with the results obtained with the clinical analyzer. Moreover, the effect of the viscosity of calibration solutions on the ISE parameters and the lifetime of the sensors were investigated.

     

Recent advances in the use of ionic liquids for electrochemical sensing

Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous properties (e.g. high intrinsic conductivity, wide electrochemical windows, low volatility, high thermal stability and good solvating ability), which make them ideal as non-volatile electrolytes in electrochemical sensors. This mini-review article describes the recent uses of ionic liquids in electrochemical sensing applications (covering the last 3 years) in the context of voltammetric sensing at solid/liquid, liquid/liquid interfaces and carbon paste electrodes, as well as their use in gas sensing, ion-selective electrodes, and for detecting biological molecules, explosives and chemical warfare agents. A comment on the future direction and challenges in this field is also presented.     

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.     

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     

General survey and microanalytical aspects of ion-selective electrodes

Summary A survey is presented of recent developments in the field of ion-selective electrodes. Special emphasis is placed on problems of electrode miniaturization and ISFET production. Different electrode types in present use are described and theories for the interpretation of electrode mechanisms are outlined. It is pointed out that the electrode potentials are due to the formation of a space charge. Different applications of ion-selective electrodes are dealt with and the problems connected with the determination of small concentrations are discussed. Attention is given to the selection of conditions under which a reliable measurement of extremely small amounts or extremely small concentrations can be ensured.     

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.     

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.     

Application of Ion-Selective Electrodes as Reference Electrodes

Abstract

Reference electrodes limiting interfering effects of conventional reference electrodes on the measurement involving ion-selective electrodes have been developed. They are constructed of a plastic body with porous plug or sleeve junction. Solid state, low impedance, ion-selective electrodes (cupric, cadmium, fluoride) in the equilibrium of corresponding ion solution are used as the half-cells. The absence of interfering ions in the electrolyte allows the determination of the ion of interest at extremely low levels without interference. The electrodes have good reproducibility and stable intercomparison potentials of ± 0.2 mV. The performance of the electrodes has been tested for the measurement of sub-ppm halide levels. Data on stability, reproducibility, effects of temperature, ionic strengthand pH is presented and compared to that of conventional reference electrodes.     

Theory and applications of ion-selective electrodes Part III

This review of ion-selective electrodes is arranged in the same way as Parts I and II. The continuous growth of the whole subject should be noted. Theory has particularly progressed through mechanistic studies. Among new types of electrodes, ISFET systems have become important. Among new applications of both solid and liquid membrane electrodes, the fluoride electrode still predominates, closely followed by potassium electrodes. In the field of biological and medical applications, the steady growth is significant. More than 800 papers published between mid-1976 and the end of 1978 are mentioned in the review.     

Lanthanide tris(β-diketonates) as ionophores for chloride ion-selective electrodes

Lanthanide tris(β-diketonates) were used as ionophores for plasticized polymer membranes of ion-selective electrodes. Electrochemical properties of the membranes were characterized, and the possibility of their use as components of chloride ion-selective electrodes was studied.     

Recent results on the dynamic response of precipitate-based ion-selective electrodes

The e.m.f. vs. time curves of the precipitate-based ion-selective electrodes have been interpreted mathematically on the basis of the desolvation of ions at the electrode surface. A new method has been suggested for the characterization of ion-selective electrodes by the half-life time of the first-order desolvation reaction.     

Theory and applications of ion-selective electrodes: Part 6

This review of ion-selective electrodes is arranged in the same way as earlier reviews of this series. The whole subject continues to grow steadily. Considerable attention has been given to clinical analysis of body electrolytes, particularly by means of automatic devices. About 800 papers published between Spring 1983 and Spring 1985 (including several omitted in Part 5) are mentioned, covering the theory of membrane phenomena, technology, fixed-state eletrodes, liquid-membranes electrodes, potentiometric biosensors and miscellaneous systems.     

PVC膜离子选择电极检测下限的优化

价格低廉、携带方便、适用浓度宽、操作简单快捷、能耗低的离子选择电极在医院、分析实验室、野外等领域得到了越来越广泛的应用。尽管如此,由于PVC膜中存在的离子流严重破坏了更低检测下限的获取,限制了离子选择电极的进一步发展。因此,本文从减小甚至消除PVC膜中存在的离子流角度出发,系统论述了优化PVC膜离子选择电极检测下限的原理和优良策略,根据收集归纳的大量数据定量阐述传感膜组成的优化、电极组装和调制、应用旋转电极以及电流极化处理等对检测下限的优化提升作用,进一步总结出各种方法的改善规律,分析它们的优势和面临的问题。提出在PVC铸膜液中要突破传统配方,减小增塑剂和离子交换剂用量,以抑制传感膜两侧的离子流,同时外加电流补偿处理等也是降低电极检测下限的有效方法,对检测下限的改善最好的可降低5个数量级。这一总结为PVC膜离子选择电极的高性能化明确了研究方向。     

Theory and applications of ion-selective electrodes part 4

This review of ion-selective electrodes is arranged in the same way as earlier reviews in this series. The growth of the whole subject approaches a steady state. Some mechanistic studies have deepened theoretical understanding. Better insight into the mechanism of liquid-membrane systems has been gained by electrolysis at the interface of two immiscible electrolyte solutions. In this field some interesting analytical applications are noted. A steady growth is shown by publications on ion-selective field-effect transistors. Otherwise the same proportion is preserved among well-established electrode types. About 800 papers published between the end of 1978 and the beginning of 1981 are mentioned.