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Öğe Investigation and comparison of the electrochemical behavior of some organic and biological molecules at various conducting polymer electrodes(Elsevier Science Bv, 1997) Erdogdu, G; Karagozler, AEElectrodes modified by the electrodepozition of conducting organic polymers such as poly(3-methylthiophene)(PMT), polypyrrole (PPY) and polyaniline (PAN) were used as chemical sensors for voltammetric analysis and flow injection detection of some organic and biological molecules. The electrochemical behaviors of catechol, ascorbic acid, hydroquinone, dopamine, epinephrine, acetaminophen and p-aminophenol were examined by differential pulse voltammetry. The electrochemical behavior of these molecules at different electrodes was compared and the effects on behavior of electrolyte type and its pH and the film thickness were systematically examined. The results showed that the proposed modified surface catalyzes the oxidation of these compounds. Electrocatalytic 'efficiency' decreases in order of poly-3-methylthiophene, polypyrrole and polyaniline. Voltammetric peak positions were affected by the nature of the electrolyte and its pH. Also, the effect of increasing film thickness was to observe increased peak heights. Polymer coated electrodes were also used in an amperometric detector for flow injection analysis of most of the these compounds. The responses of the polymer electrode were 5-15 times larger as compared with those of bare platinum. PMT showed improved performance as an amperometric detector for flow injection analysis systems over other types of polymer electrodes. Detection limits as low as 10(-8)-10(-9) M were achieved using the PMT, compared with 10(-6)-10(-8) M using platinum electrodes In the flow injection analysis, with increasing molecular weight of analyte molecules was to observe decreased peak heights. (C) 1997 Elsevier Science B.V.Öğe Investigation of polymerization parameters affecting dopamine selectivity of a polymeric membrane(Springer-Verlag, 2000) Ekinci, E; Erdogdu, G; Karagözler, AEBy means of electrochemical oxidative polymerization, poly (1,3-phenylenediamine) films on a gold electrode were prepared at a potential of 0.8 V. The permeation properties of polymeric films at the different thickness were investigated by cyclic and differential pulse voltammetry techniques. Voltammetric studies showed that polymeric film at the 1.2 mC thickness exhibited selective permeation for dopamine while rejecting ascorbic acid. Then, all the polymerization parameters affecting the permselective characteristics were systematically investigated and the optimal values were determined. Moreover, stability of polymeric membrane was examined. The results showed that polymeric membrane, owing to permselective character, could be used as a dopamine selective membrane.Öğe Preparation and electrochemical behavior of dopamine -: selective polymeric membrane(Springer Verlag, 2000) Erdogdu, G; Ekinci, E; Karagözler, AEo-toluidine was polymerized electrochemically using constant-potential electrolysis at a gold electrode surface. Electrochemical behavior of dopamine and ascorbic acid at the polymer electrode prepared in this manner was examined by cyclic and differential pulse voltammetry techniques. The influence of chemical and electrochemical variables on dopamine selectivity of the polymer electrode was systematically investigated and the optimal values for each parameter were determined. Experimental results showed that optimized polymeric membrane exhibited selectivity for dopamine while blocking ascorbic acid. Therefore, it is claimed that poly (o-toluidine) film can be used as a dopamine-selective polymeric membrane in the presence of ascorbic acid.Öğe Preparation, optimization, and voltammetric characteristics of poly(o-phenylenediamine) film as a dopamine-selective polymeric membrane(John Wiley & Sons Inc, 2001) Ekinci, E; Erdogdu, G; Karagözler, AEPoly(o-phenylenediamine) films were electrochemically prepared on gold electrodes from the corresponding monomer in an aqueous solution at a constant potential. The polymeric films prepared in this one-step procedure were found to be thin and insoluble in the aqueous solution. Cyclic and differential pulse voltammetric techniques were used to examine the permeation properties of ascorbic acid and dopamine at the resultant polymeric film electrode. Then, the effects of the chemical and electrochemical variables (e.g., film thickness, polymerization potential, concentrations of monomer and electrolyte) on the permselectivity characteristics of the polymeric film were systematically investigated and the optimal values for each parameter were determined. Furthermore, it was found that the optimized polymer electrode was found to be stable for the successive runs. As a result, it is claimed that poly(o- phenylenediamine) film can be used as a dopamine-selective polymeric membrane. (C) 2000 John Wiley & Sons, Inc.Öğe Selective voltammetric detection of epinephrine in the presence of ascorbic acid at poly(4-methoxyphenol)-modified electrode(Maik Nauka/Interperiodica, 2002) Erdogdu, GA gold electrode was modified with electropolymerized films of 4-methoxyphenol by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was then used to determine epinephrine (EP) in the presence of a high concentration of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity EP/AA were affected by the potential window used for the polymerization. For polymerization between 0 and 1.3 V, the peak potentials recorded in a phosphate buffer solution (pH = 7.2) were 516 and 312 mV vs. Ag/AgCl for EP and AA, respectively. In addition the effects of pH and the type of electrolyte on the linearity range and detection limit are investigated. The detection limit for 3s-test is 0.1 muM. The high selectivity and sensitivity for epinephrine was found to be due to charge discrimination/analyte accumulation.Öğe A sensitive voltammetric method for the determination of diazinon insecticide(Pleiades Publishing Inc, 2003) Erdogdu, GA sensitive voltammetric method is developed for the determination of diazinon, an organophosphorus pesticide, using a Nafion(R)-coated glassy carbon electrode as an enrichment film. The analysis of diazinon in aqueous solutions using sensitive instrumental methods has gained importance. Investigation of the electrochemical behavior of diazinon on a Nafion(R)-coated glassy carbon electrode reveals the presence of a specific oxidation peak of analytical significance. The experimental parameters, such as pH, film thickness, pre-concentration potential, preconcentration time, and square-wave voltammetric parameters were optimized. Using this method, a linear calibration curve for diazinon was obtained up to 5 muM range in pH 1 citrate buffer solution with a detection limit (SIN = 3) of 75 nM.Öğe Voltammetric resolution of ascorbic acid and dopamine at conducting polymer electrodes(Marcel Dekker Inc, 1996) Erdogdu, G; Mark, HB; Karagozler, AEElectrochemical behavior of dopamine and ascorbic acid binary mixture was examined by cyclic voltammetry and the analysis of a each component was performed by differential pulse voltammetry. The electrochemical behavior of these molecules on poly-3-methylthiophene, polypyrrole, polyaniline electrodes were compared. The effects of electrolyte type and its pH, and the film thickness on the voltammetric resolution of these molecules were systematically examined. At all the modified electrodes both dopamine and ascorbic acid peaks shifted their positions to more negative potentials with increasing pH, difference between the positions remaining almost constant. Type of electrolyte seems to have an effect on ascorbic acid peak only at the poly-3-methylthiophene electrode. The effect of increasing film thickness was to observe increased peak heights.
