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

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.