Publikace vydané Univerzitou Pardubice / Published by the University of Pardubice
Stálý URI pro tuto komunituhttps://hdl.handle.net/10195/37631
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Článek Otevřený přístup peer-reviewedpublished Determination of hydrogen peroxide with sensors based on heterogenous carbon materials modified with manganese dioxide(Univerzita Pardubice, 1997) Schachl, Klemens; Alemu, Hailemichael; Kalcher, Kurt; Ježková, Jitka; Švancara, Ivan; Vytřas, KarelThree different types of MnO2-modified electrodes were investigated on their electrochemical response towards hydrogen peroxide: a bulk-modified carbon paste electrode, a film-modified carbon paste electrode and a film-modified screen printed electrode. The sensors were characterized by voltammetric (cyclic voltammetry, linear sweep voltammetry) and amperometric methods (stationary and flow conditions). The best responses were obtained with a MnO2 filmmodified screen printed carbon electrode which could be used as an electrochemical detector in flow injection analysis (FIA) using a NH3/NH4Cl buffer (0.2 M, pH 9.5) as a carrier. With FIA a detection limit (3σ) of 0.26 µg 1−1 could be achieved; the peak current was linear to the H2O2 concentration from 1 to 200.000 µg 1−1. The method could be successfully applied to the determination of H2O2 in various samples (cosmetic and medical products, rain water). With flow injection a sample frequency of 60 h−1 can be achieved.Článek Otevřený přístup peer-reviewedpublished Recent progress in the development of electrochemical carbon paste sensors(Univerzita Pardubice, 1997) Kalcher, Kurt; Schachl, Klemens; Švancara, Ivan; Vytřas, Karel; Alemu, HailemichaelIn this review an overview is given of some recent trends in developing electrochemical sensors that are based on heterogeneous carbon materials. Their main characteristic is a usually non-conducting liquid or solid matrix, into which conductive carbon particles are embedded. Typical representatives of such types of sensors are carbon paste electrodes (CPE), solid carbon composite electrodes (CCE), and screen printed carbon electrodes (SPCE). Main emphasis in this article is put on summarizing trends and strategies of the development of carbon paste sensors during the past few years (365 references).Článek Otevřený přístup peer-reviewedpublished Voltammetric determination of heavy metals in natural waters and biological samples by using a chemically modified carbon paste electrode(Univerzita Pardubice, 1997) Iliadou, Efterpi N.; Girousi, Stella T.; Voulgaropoulos, Anastasios N.; Vytřas, KarelThe behaviour of copper, lead and cadmium was studied with a new chemically modified carbon paste electrode, with different supporting electrolytes (HCl, HClO4, H2SO4, NH3-NH4Cl). The optimum conditions for the determination of the above mentioned metals were studied either separately or simultaneously in mixtures of 2 or 3 of them. The method for their simultaneous determination was more sensitive after deposition of a mercury film "in situ" after addition of Hg(II). Detection limits are 5.00 µg l−1, 7.00 µg l−1, 2.00 µg l−1 for copper, cadmium and lead, respectively. The relative standard deviation at a concentration level of 6.00–7.50 ppb, varies within the range 5.00–8.00 % for 90 sec of preconcentration time. Copper, cadmium and lead were determined in synthetic as well as in natural samples by anodic stripping voltammetry (ASV).Článek Otevřený přístup peer-reviewedpublished Voltammetric determination of ascorbic acid in foodstuffs using modified carbon paste electrodes(1997) Nováková, Marcela; Kalcher, Kurt; Schachl, Klemens; Komersová, Alena; Bartoš, Martin; Vytřas, KarelApplication of differential pulse cathodic stripping voltammetry for determination of ascorbic acid in foodstuffs have been investigated using a carbon paste electrode modified by cobalt(II) phthalocyanine, which was found to facilitate its oxidation and to decrease the necessary overvoltage. The method showed a good linearity up to 70 ppm of ascorbic acid with a detection limit of 0.8 ppm. When applied to analyse the real samples (fruit juices), the results agreed well with those obtained by traditional titrimetric determination.Článek Otevřený přístup peer-reviewedpublished Study of conditions for voltammetric determinations of iodine at carbon paste electrodes(Univerzita Pardubice, 1997) Konvalina, Jiří; Švancara, Ivan; Vytřas, KarelA method has been developed for the determination of iodine in the form of iodide at a carbon paste electrode (CPE) with tricresyl phosphate as a pasting liquid using differential pulse cathodic stripping voltammetry. The determination is based on the combined preconcentration mechanism of iodide anions from acidic media, probably forming ion-pairs with protonated molecules of a pasting liquid, then oxidizing to iodine at +0.7 V (vs. Ag/AgCl) and extracting onto a CPE. The detection limit of 30 µg l−1 was obtained. The procedure was successfully applied to analyse real samples of mineral water and table salts containing either iodide or iodate. The results were verified by means of reference methods, e.g. ICP-MS technique, recovery determinations and iodometric titrations.Článek Otevřený přístup peer-reviewedpublished Solid electrodes plated with metallic films(Univerzita Pardubice, 1997) Švancara, Ivan; Vytřas, Karel; Kalcher, KurtThis review article surveys basic characteristics and typical electrochemical properties of solid electrodes employed as the supports for the preparation of metallic film electrodes, predominantly of mercury- and gold film electrodes. Individual types of metallic film electrodes are critically compared, including their confrontation with classical voltammetric sensors such as hanging mercury drop electrode or solid gold electrode. Discussed are scope and limitations of metallic film electrodes in anodic stripping voltammetry. Practical applications of these electrodes are demonstrated using some typical examples based on authors' experience with mercury- and gold film plated carbon paste electrodes.Článek Otevřený přístup peer-reviewedpublished Some new methods of indirect determination of metals based on adsorption and complexation properties of Arsenazo III azo dye(Univerzita Pardubice, 1997) Komersová, Alena; Bartoš, Martin; Kalcher, Kurt; Vytřas, KarelVoltammetric properties of Arsenazo III were studied in view of its exploitation for trace analysis of metal ions using adsorptive stripping voltammetry. Conditions for determinations of uranium and aluminium were optimized and the corresponding procedures suggested.Článek Otevřený přístup peer-reviewedpublished Studies on potentiometric titrations using simple liquid membrane-based electrodes: Coated wires vs. Carbon pastes(Univerzita Pardubice, 1997) Vytřas, Karel; Ježková, Jitka; Dlabka, Vilém; Kalous, JaromírAn overview is given on the use of simple potentiometric sensors to monitor titrations based on various principles. Earlier results obtained with polymeric membrane electrodes of the coated-wire type are compared to those taken with carbon paste electrodes. Both the types can be recommended as simple and inexpensive sensors suitable to monitor titrations based on ion-pairing principles. It is expected that an organic solvent present in both the sensors (a membrane plasticizer or pasting liquid) is saturated with an ion-pair formed within such a titration on extraction principles, thus giving selective ion-exchanging electrodes. Although in acid-base titrations and some of determinations based on both oxidation-reduction and precipitation reactions the potential breaks can also be obtained, authors prefer monitoring of them with other suitable sensors.Článek Otevřený přístup peer-reviewed Testing of some nitro compounds as new plasticizers of polymeric membrane-based electrodes(Univerzita Pardubice, 1997) Vytřas, Karel; Kadeřábková, Milena; Socha, Jaromír;An ion-pair formation-based titration monitored by simple polymeric membrane-containing electrodes of the coated-wire type proved as a procedure suitable for quick testing of new plasticizers. In the titration of a model compound, extraction capabilities of individual plasticizers can be estimated from the magnitude of the potentiometric titration break. A proper amount of a plasticizer needed for preparation of the membrane can be evaluated graphically as a maximum value of this break. However, the lifetime of the membranes must also be taken into account. From the 15 nitro compounds under test, all 2,4-dinitrophenyl n-octyl, 2-nitrophenyl n-octyl and 2-nitrophenyl 2-ethylhexyl ethers proved to be the most suitable from both the criteria (the lifetime of the sensing electrode as well as the value of the potential break). Dialkyl 3-nitrophthalates can also be recommended giving the titration breaks equivalent to those obtained with 2-nitrophenyl alkyl ethers. With other nitro compounds tested, either the potential break is sharp enough but the lifetime of corresponding sensors is more or less shortened, or the break magnitude is depressed.Článek Otevřený přístup peer-reviewedpublished Voltammetric determinations at polymeric colloidal gold paste electrodes – preliminary communication(Univerzita Pardubice, 1997) Sikora, Eugen; Vytřas, KarelA new method of preparation of polymeric poste electrodes containing metallic gold colloid is described and their applications for the determination of mercury(II) in water samples are preliminarily tested. The main goal of the use of these electrodes lies in the simple renovation of their active surface. However, the reproducibility of the voltammetric records still depends on the way of the electrode pretreatment and, from this point of view, the development of a general procedure for some determinations, e.g. of mercury(II), still represents a real challenge with many problems which have to be solved.