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.