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  • 1
    ISSN: 1040-0397
    Keywords: Heparin ; Modified electrodes ; Electrocatalysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical oxidation of full-size heparin (13-15 kDa) is demonstrated in 1 M H3PO4 at a glassy carbon electrode coated with a ruthenium oxide film. The pathway apparently is analogous to chemical oxidation by periodate. By comparison to currents from inorganic species, it is apparent that only about 2 electrons per mole are involved. Flow injection analysis (FIA) allowed determinations down to 2 μM heparin, but the calibration plot was nonlinear. Low molecular weight heparin (5-6 kDa) was not electroactive with this system. In basic solution at a glassy carbon electrode that is modified with a film of Cu2O, both full-size and low molecular weight heparin are oxidized. The pathways involved oxidative desulfation and attack on saccharide units with evolution of CO2. Linear calibration plots which extended into the sub-μM level were obtained by FIA. The detection limits, which were based on a value of 3 for the ratio of the signal to the standard deviation of replicates, were 9 nM for full-size and 20-30 nM for various low molecular weight heparin samples.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 976-981 
    ISSN: 1040-0397
    Keywords: Modified electrodes ; Electrocatalysis ; Ruthenium ; Nitrosamines ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polishable bulk-modified electrode is described that contains polymeric-mixed valent ruthenium oxide with cyano cross-links (mvRuCN) as a catalyst. Because mvRuCN is not available as an isolated compound, it was electropolymerized on graphite powder that was subsequently formed into a conducting composite with epoxy. Except for promoting oxidations at a more positive potential, this composite behaved the same as mvRuCN films on glassy carbon. Electrocatalytic oxidation of various N-nitrosamines, As(III), glutathione, isotocin, and myoglobin was observed. Flow-injection analysis of 50 μM N-nitrosodi-n-propylamine with amperometric detection at the bulk-modified composite electrode yielded currents of 2.5 ± 0.1 μA (5 trials) when the carrier solution is pH 1.5 phosphate buffer. The use of a micellar carrier,pH 1.5 phosphate buffer in 0.01 M hexadecyltrimethylammonium chloride, decreased the sensitivity of the flow-injection amperometric determination of N-nitrosodi-n-phenylamine by 50%, but otherwise, the behavior of the electrode was unchanged. The major advantages of the bulk-modified electrode over the surface-modified electrode jras the long-term stability (at least several months with dry storage) and polishability. Regarding trie latter, 19 replicates of the oxidation of As(III) yielded a relative standard deviation (RSD) of the current response of 3% when the surface was polished between each trial.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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