452629.fig.003
Figure 3: Differential pulse voltammograms of 70 μM DA and 50 μM PAR at (a) GC and (b) MWCNTs/GCE in 0.1 M phosphate buffer solution (pH 7). Other conditions: open circuit,  s, pulse amplitude = 50 mV, scan rate = 10 mV·s−1, interval time 0.5 s, modulation time = 0.2 s, and step potential = 5 mV.