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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.

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.

Comparaison entre les structures du chlorure de (uree) mercure et du chlorure de bis(ethyluree) mercure, donnant un exemple de l'effet de deformation, introduite dans la molecule uree par le pont ethylene, sur les proprietes de coordination de l'uree