3. Results and discussion
3.1. Electrochemical behavior of BPR
In this study the oxidation of BPR was first evaluated at CPE electrode by cyclic voltammetry method in 0.2 M phosphate buffer pH 3.0. Typical results attained for a potential scan from 0.3 to 1.0 V are exhibited in Fig. 1. Curve a shows the electrochemical behavior of BPR at CPE in the absence of SDS. As it is seen, the oxidation peak potential for BPR at the CPE is 0.64 V. As can be seen in curve b, cyclic voltammogram of BPR in the addition of SDS exhibits well defined increase in the oxidation
peak current at the surface of CPE (Fig. 1b). SDS could be spontaneously adsorbed on the CPE surface and formed a bilayer through hydrophobic interactions between the hydrophobic long chain of SDS
molecules and the paraffin oil in the carbon paste and sulfate terminal group oriented outside. The adsorbed SDS organized in a dense monolayer on surface would accumulate BPR by electrostatic interaction between positively charged BPR and negatively-charged sulfate group of SDS. Consequently BPR's concentration increases on the electrode surface. However, SDS can improve the electrochemical process of BPR and significantly increase the oxidation peak current.