Zinc-Selective Membrane Electrode Based On 5, 6, 14, 15-Dibenzo-l, 4-Dioxa-8, 12-Diazacyclopentadecane-5, 14-Diene

Potentiometric zinc ion sensor based on honeycomb-like NiO nanostructures

In this study honeycomb-like NiO nanostructures were grown on nickel foam by a simple hydrothermal growth method. The NiO nanostructures were characterized by field emission electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques. The characterized NiO nanostructures were uniform, dense and polycrystalline in the crystal phase. In addition to this, the NiO nanostructures were used in the development of a zinc ion sensor electrode by functionalization with the highly selective zinc ion ionophore 12-crown-4. The developed zinc ion sensor electrode has shown a good linear potentiometric response for a wide range of zinc ion concentrations, ranging from 0.001 mM to 100 mM, with sensitivity of 36 mV/decade. The detection limit of the present zinc ion sensor was found to be 0.0005 mM and it also displays a fast response time of less than 10 s. The proposed zinc ion sensor electrode has also shown good reproducibility, repeatability, storage stability and selectivity. The zinc ion sensor based on the functionalized NiO nanostructures was also used as indicator electrode in potentiometric titrations and it has demonstrated an acceptable stoichiometric relationship for the determination of zinc ion in unknown samples. The NiO nanostructures-based zinc ion sensor has potential for analysing zinc ion in various industrial, clinical and other real samples.

Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade

Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, polynapthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylenedioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, polycarbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

Preparation of a cimetidine ion-selective electrode and its application to pharmaceutical analysis

A novel cimetidine ion-selective electrode is prepared, characterized and used in pharmaceutical analysis. The electrode incorporates PVC-membrane with cimetidine-phospohotungstate ion pair complex. The electrode exhibits a Nernstian response for cimetidine in the concentration range 1.0 x 10(-5)-1.0 x 10(-2) M with a slope of 58+/-1 mV per decade. The limit of detection is 5.0 x 10(-6) M. The electrode displays a good selectivity for cimetidine with respect to a number of common foreign inorganic and organic species. It can be used in the pH range 3.0-5.5. The membrane sensor was successfully applied to the determination of cimetidine in its tablets as well as its recovery from a urine sample.