Under the optimum experimental conditions of pH 9–10, deposition time 60 s, deposition potential 0.45 V, pulse amplitude 50 mV, starting potential 0.0 V and scan rate 60 mV/s, the DP CSV of SP showed that, the Ip,c1 at 1.1 V was not sensitive and independent on SP concentration, while the Ip,c2 at 1.40 V vs. Ag/AgCl increased linearly on
increasing the drug concentration in the range from 1.2 10 10 to 9.6 10 7 M (Fig. 5). Above 9.6 10 7 M,
the Ip,c2 tended to level off because of the adsorption saturation with the following a regression equation: