engleski

Development and application of ion-selective electrode membranes doped with metal oxides nanoparticles for iron cations determination

Electrochemical sensors, including potentiometric ones, have the ability to transform the effect of electrochemical interaction between analyte and electrode into a useful signal. Potentiometric sensors were first used as an analytical technique in the early twentieth century and experienced rapid development in the 1970s. Today, they are used in many technical and scientific fields. Many of them are used in environmental, clinical and drug analysis. Ionselective electrodes, as an important member of the electrochemical sensor family, have been in the center of electrochemical research for nearly a century. Their continuous development and combination with other scientific and technological improvements have ensured them a wide range of applications. Properties of ion- selective electrodes such as non-destructive and simple method, low cost, small-sized, short-time for doing a measurement and reliable have made them valuable competitors among other, more sophisticated methods for the analysis of real-samples. Nanotechnology is a scientific field dealing with the fabrication of nanometer-sized products and has received great attention and development over time, especially during last decade. Since the nano-sized structures have completely different and unique physical, chemical and biological properties than the same matter on a larger size scale, they have found applications in many scientific fields and this phenomenon is mainly related to their large surface-tovolume ratio. The combination of these two aforementioned fields of science in the form of the development of new nanoparticle-modified ion- selective electrodes led to the improvement of many properties of ion-selective electrodes, especially the sensitivity, linear range, and detection limit of the analyte. This is the main topic of this research and thus, presented in a dissertation. In this work, a new ion-selective membrane incorporated into a newly designed electrode body and modified with various nanoparticles is presented, as well as the synthesis and characterization of all used modificators. An ion-selective membrane based on ferric phosphate with addition of silver sulphide and polytetrafluoroethylene as matrix was successfully used for the determination of ferric cations with a slope of −20.53 mV dec−1 and detection limit of 2.41∙10−5 mol L−1 . After establishing of ideal composite ratio for the above mentioned three components, a new electrode body design was introduced to ensure miniaturisation and better conductivity. The improved electrode body design enabled greater repeatability of results, thus making the proposed sensor suitable for the determination of ferric cations in pharmaceutical samples. The addition of nanoparticles improved some of the key ion- selective electrode properties. However, not only the application, but also the synthesis and characterization processes, as well as the influence of various synthesis parameters and surfactant addition on the composition of the obtained products, are studied and explained in detail in this doctoral thesis. Special attention is set on microwave-assisted hydrothermal synthesis of iron oxide nanoparticles, which are perspective candidates for the electrochemical sensing field as efficient charge transfers. In addition to iron oxides, alumina and boehmite were also used for electrode modification, and it was found that pure phase hematite had the most attractive effect on ion-selective electrode properties. Ion-selective electrode modified with 0.25% of hematite showed Nernstian response with a slope of −19.75 mV dec−1 in the linear range from 1.2⸱10−6 mol L−1 to 10−2 mol L−1 and a detection limit of 1.01⸱10−6 mol L−1 for the determination of ferric cations. Since iron is one of the most abundant elements in the world, and also found in many aspects of human life, whether inside or outside the human body. Although iron is necessary for the normal development and functioning of the human body, a deviation of its concentration from the reference values in the body, whether an excess or a deficiency, affects the development of many disorders and consequently diseases. Therefore, the development of new analytical tools for accurate, selective and rapid measurement of iron concentrations would be of great help both as a diagnostic tool for disorders of human metabolism and as a tool for research and better understanding of iron metabolism in human body.

ion-selective electrodes ; iron(III) cations ; nanoparticles ; potentiometry

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