In Situ Recalibration of Ion Selective Electrodes

Reference electrode drift resulting from the exchange of ions at the solution/reference electrode chamber interface is the number one reason why ion selective electrodes and pH sensors in particular require...

Ionophore-Based Ion-Selective Electrodes: Signal Transduction and Amplification from Potentiometry

Ionophore-based ion-selective electrodes (ISEs) are traditionally operated with potentiometry by measuring the open circuit potential against a reference electrode. However, the sensitivity of ISEs is limited by the well-known Nernstian...

The New Ion-Selective Electrodes Developed for Ferric Cations Determination, Modified with Synthesized Al and Fe−Based Nanoparticles

The solid-state ion-selective electrodes presented here are based on the FePO4:Ag2S:polytetrafluoroethylene (PTFE) = 1:1:2 with an addition of (0.25–1)% microwave-synthesized hematite (α-Fe2O3), magnetite (Fe3O4), boehmite [γ-AlO(OH)], and alumina (Al2O3) nanoparticles (NPs) in order to establish ideal membrane composition for iron(III) cations determination. Synthesized NPs are characterized with Fourier-Transform Infrared (FTIR) spectroscopy, Powder X-Ray Diffraction (PXRD), and Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). The iron oxides NPs, more specifically, magnetite and hematite, showed a more positive effect on the sensing properties than boehmite and alumina NPs. The hematite NPs had the most significant effect on the linear range for the determination of ferric cations. The membrane containing 0.25% hematite NPs showed a slope of −19.75 mV per decade in the linear range from 1.2∙10−6 to 10−2 mol L−1, with a correlation factor of 0.9925. The recoveries for the determination of ferric cations in standard solutions were 99.4, 106.7, 93.6, and 101.1% for different concentrations.

pH-metric method determining the solubility and solubility products of slightly soluble salts of arbitrary composition

The developed method of determining KS from pH metric data has a number of advantages compared to those used traditionally. First, in place of the residual concentrations of the salt components, only the pH value of the saturated solution is used in the derived expressions. Thus, the number of independent variables, which need to be measured experimentally, is reduced. Furthermore, the potentiometric method, used to determine the pH, is sufficiently accurate, simple and universal and does not necessitate the use of ion-selective electrodes. At the same time, the residual concentrations are usually measured by chemical methods, which are inferior in most cases, for several reasons, compared to the potentiometric method. Second, the KS value calculated by the developed method has a thermodynamic character. The organization of the experiment must be appropriate to the applied equations. Therefore, it is necessary to draw attention to the need for high accuracy in the process of preparing the initial solutions, because the initial concentrations of the precipitate components are included in the calculation formulas. The developed method for determining Ks can be applied for systems of any degree of complexity, which contain additional complexing agents.

Ion-selective Electrodes Based on PVC Membranes for Potentiometric Sensor Applications: A Review

Ion-selective electrodes (ISEs) are potentiometric sensors used to measure some of the most critical analytes in environmental laboratory. Recently ion sensors are taking place of various analytical techniques, as they provide a convenient and fast method of electroanalysis. Ion-selective electrodes are simple, relatively inexpensive, robust, durable, and ideal to be used for the detection of heavy metal ions. Important characterisctics of ISEs are selectivity, response time, detection limit, working range, effect of pH etc. Lot of research work is being done for the formation of ISEs by using polymeric membrane incorporated with ionophores or electroactive material. Various types of Schiff bases, macromolecules and metal complexes may be used as ionophores along with plasticizer, ion-excluder for the membrane preparation. Ion-selective electrodes will be optimized for pH range, selectivity, sensitivity, working concentration range and lifetime before their use as sensor electrode for determining the concentration of ions in solution. Various researchers are working in the field to develop Ion-selective electrodes which shows better selectivity and sensitivity than the previously reported electrodes and can be used as electrocatalysts. These ISEs can be used as electrochemical sensors for the analysis of food products, drinking water, beverages, fertilizers, and for the analysis of sample containing toxic substances.

Application of polyaniline nanofibers for the construction of nitrate all-solid-state ion-selective electrodes

The application of polyaniline nanofibers doped with chloride and nitrate ions (PANINFs-Cl and PANINFs-NO3) in potentiometry was described. Both kinds of nanofibers were used as an ion-to-electron transducer in ion-selective electrodes with solid contact (SCISEs). Extensive research on the properties of the nanofibers themselves (SEM, UV–Vis spectroscopy, FTIR) and the constructed electrodes (potentiometric methods, electrochemical impedance spectroscopy) has been carried out. Basic analytical parameters of electrodes containing various nanofibers contents in the ion-selective membrane and with nanofibers as an intermediate layer were determined. It was found that application of PANI nanofibers resulted in improvement of electrode performance (among others, better stability and reversibility of the electrode potential). The obtained sensors were characterized by a high slope of the calibration curve, a wide measuring range and a fast response time. Moreover, they were insensitive to change of redox potential, as well as light and the presence of oxygen in the solution, what is important from a practical point of view. They were also successfully used for nitrate determination in real environmental samples.