3.2. Optimization of the conditions for the determination of BPR
Differential pulse voltammetry (DPV) was applied to further
increase the recognition sensitivity of BPR.
The pH of the phosphate bufferwas altered in the range of 2.0 to 6.0
with the aim of evaluating the best pH value. Fig. 2 shows the differential
pulse voltammograms of 0.08 μMBPR at CPE in the presence of SDS.
The anodic peak current of BPR achieves the highest value at the pH
value of 3.0, therefore this pH value was chosen for further study.
Also, peak potential shifted to negative value with increasing of pH.
The inset B of Fig. 2 displayed the relationships between the oxidation
peak potential of BPR and pH. A linear relationship with equation of E
(V) = −0.0457 pH + 0.7466 (R2 = 0.9948) suggests that equal electron
and proton are involved in the oxidation of BPR at the CPE [31].
The concentration of SDS for the determination of BPR was optimized,
which varied from 0.24 μM to 0.24 mM. Increasing the concentration
of SDS in the phosphate buffer solution led to an increase in
the oxidation peak current due to increase the adsorbed surfactantmolecules.
Themaximumpeak currentwas obtained at 0.24mMSDS. However,
with further increasing concentration of SDS, the oxidation peak
current remains unchanged. The reason for this behavior probably lies
on the surface saturation at 0.24 mM SDS. Therefore, this value of SDS
was chosen for next experiments.