Electrochemical oxidation and determination of heparin at electrodes modified with ruthenium oxide or copper oxide

Abstract

Abstract The electrochemical oxidation of full‐size heparin (13–15 kDa) is demonstrated in 1 M H 3 PO 4 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 Cu 2 O, both full‐size and low molecular weight heparin are oxidized. The pathways involved oxidative desulfation and attack on saccharide units with evolution of CO 2 . 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.