Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/1447
Authors: Bachheti, Neeta
Issue Date: 2007
Abstract: The chemical modification of electrodes is a field of growing interest in electroanalytical chemistry. Chemically modified electrodes (CMEs) have drawn much attention in the field of electrochemistry due to their easy fabrication, excellent sensitivity, fast response, good selectivity and low cost. One of the most significant properties of the CMEs is their ability to catalyze the oxidation and reduction of electroactive species which exhibit high peak potential at conventional and unmodified electrodes. It is for this reason that in recent years the increasing use of CMEs for electroanalytical measurement of a variety of metal ions and organic species of biological, clinical and pharmaceutical importance has been reported. In view of the importance of ion-sensors in diverse fields, extensive efforts were initiated during the last two decades to develop sensors for various ions. Such sensors have potential application in various spheres of life, viz., in ionmonitoring and in the analysis of sea-water, soils, industrial effluents, clinical areas and environmental monitoring. In view of the importance of electrochemical investigations followed by analysis of biological fluids and pharmaceutical formulations and considering the unique properties of modified electrodes, an attempt has been made in the present dissertation to determine various compounds of biological significance such as purines, indoles etc. and commonly used drugs using fullerene-C6o-modified glassy carbon and gold nanoparticles modified indium tin oxide (Au/ITO) electrodes. Efforts have also been made in the present thesis to develop sensors for some toxic metals (viz., copper (II), zinc 11 (II) and nickel (II)). For simplicity and clarity, the results of the investigation are organized in the dissertation as follows: The first chapter of the thesis is "General Introduction" and presents a brief review and significant results relevant to the present study on the electrochemical determination of various biologically important compounds particularly purines, indoles, drugs and metal ions selected. The chapter also highlights the salient features of the voltammetric techniques, the properties of the modified electrodes used, the theory of membrane potentials and methodology. Heterocyclic compounds including purines and their derivatives and indolic neurotransmitters play an important role in biological systems and hence their determination has become increasingly important in the field of biomedical research. The determination of some biologically important compounds (viz. uric acid, adenosine, guanosine, dopamine and serotonin) was therefore considered for investigation and results obtained are presented in the second chapter of the thesis which has been subdivided in three parts. The first part deals with uric acid, the determination of concentration of which is of paramount importance because change in its concentration leads to numerous diseases and physiological disorders. Fullerene-C60-modified glassy carbon electrode was utilized for the determination of uric acid. It was observed that the presence of fullerene-C6o film at the electrode surface resolved the overlapped voltammetric peak response of uric acid and ascorbic acid coexisting in a solution obtained at bare glassy carbon electrode into two well-defined peaks. A linear calibration in graph was obtained for uric acid over the range 0.5 uM -700 uM in linear sweep voltammetry with a detection limit and sensitivity of 0.20 uM and 0.0215 uAuM"1, respectively. The presence of physiologically common interferents has also been studied. The method was then successfully applied for the determination of uric acid in human urine samples, thus offering a possibility for extending this technique to the routine analysis of uric acid in clinical samples. The second part of this chapter deals with the determination of purine nucleosides which are well-known for their metabolic and biological effects in human system, making their analysis highly desirable. A simple and reliable voltammetric procedure has been adopted utilizing fullerene-C6o-modified glassy carbon electrode for the simultaneous determination of adenosine and guanosine. The peak current increased linearly with increase in adenosine and guanosine concentration in the range 0.5 uM-1.0 mM. The detection limits have also been determined. Upto four-fold excess of the interferents viz., hypoxanthine, xanthine, uric acid and ascorbic acid did not affect the peak response. The proposed procedure has also been applied to detect both the nucleosides in spiked human blood plasma and urine samples. Dopamine and serotonin are two important neurotransmitters whose neurodegeneration leads to neurological disorders. Since their levels in serum provide information of diagnostic value in such disorders, the determination of their concentration is vital in the field of clinical research. In the present study, the feasibility of the Au/ITO electrode for the simultaneous determination of dopamine and serotonin in the presence of ascorbic acid was investigated with IV our interest mainly focused on attaining a very low detection limit of dopamine in the presence of interferents such as serotonin and ascorbic acid. Linear calibration curves were obtained in the range 1.0 nM-0.5 mM and 10 nM-0.25 mM with a detection limit of 0.5 nM and 3.0 nM for dopamine and serotonin, respectively at the Au/ITO electrode. The results are compiled in the third section of chapter 2. .....................
Other Identifiers: Ph.D
Research Supervisor/ Guide: Goyal, R. N.
Gupta, V. K.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (chemistry)

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