Amperometric determination of hydrogen peroxide by direct and catalytic reduction at a copper electrode

In a buffer solution at ambient temperature and dissolved oxygen concentration, pH 6.7, copper electrodes could be cycled between the Cu(0)/Cu(II) redox states, by cycling the potential between −0.8 and +0.3 V vs. SCE. At 1 V s−1, the reduction of Cu(II) proceeded with a rate constant of 12.3 s−1 (αC = 0.16, αA = 0.93). The redox couple catalysed the reduction of hydrogen peroxide, with a second-order rate constant of approx. 25 ± 10 M−1 s−1. Amperometric determination of H2O2 at −0.25 V gave a limit of detection (2 × noise) of 1.2 μM (sensitivity = 0.211 mA mM−1 cm−2 up to 2.0 mM), with a response time (steady-state) of 3 to 4 s. A 1 μM change in the O2 concentration gave approx. a 0.04% change in the H2O2 sensitivity. The presence of H2O-soluble copper-complexing anions at low concentrations gave a change in the H2O2 response. At higher anion concentrations (> 20 mM), the rate of electron transfer from the metal was faster than the rate of Cu(II) dissolution. A copper micro-band electrode was used to determine H2O2 in a mixture of glacial acetic acid and chloroform.