Fig. 4

CVs obtained on the PVP-GR/GCE in 0.1 M PBS (pH 6.0) in the absence (black) and presence of 1.0 mM AA (red), 20 μM DA (green), 50 μM UA (blue) and a mixture solution containing 1.0 mM AA, 20 μM DA and 50 μM UA (brown), respectively. Scan rate: 100 mV s⁻¹