Fig. 1

a Square wave voltammograms (frequency: 100 Hz, amplitude: 40 mV, step potential: 1 mV) for the oxidation of THC, seen at +0.37 V (vs. SCE), on the graphite/dioctyl phthalate paste electrode (black line) and the graphite/mineral oil paste electrode (red line). The measurement was obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 80 μM THC, for 3 min. b Comparison of the peak currents obtained with the two carbon paste electrodes (black squares: graphite/dioctyl phthalate paste, red circles: graphite/mineral oil paste). The measurements were obtained in a deoxygenated BBS (0.1 M KCl, pH = 10.0, 298 K), after immersing the electrode in identical stationary solutions that contained 7.0 – 80 μM THC, for 3 min. The errors relate to separate electrode preparations