The observed oxidation peak of antimony at a gold-modified
CSPE is also strongly affected by parameters such as pH,
Edep, and tdep. Previous experiments had demonstrated that the
application of this method to the analysis of antimony should
be performed in an acid medium. For this reason a pH 2
Britton–Robinson buffer solution was chosen as the supporting
electrolyte.
In order to obtain a sensitive analytical signal a 22 central
composite design was carried out with the remaining factors.
From this design, itwas deduced that deposition time has a much
greater influence than deposition potential, as it was found that
the response for antimony increased in relation to the deposition
time (Fig. 4a). For which reason, there was no satisfactory
response surface with which to establish the optimal values.
From an experimental point of view, the use of a long deposition
time is satisfactory for the determination of low Sb(III)
concentrations. For higher concentrations of Sb(III), short deposition
times are more appropriate in order to avoid the saturation
of electrode surface. In addition, several experiences were performed
to select the most suitable deposition potential, as can
be seen in Fig. 4b. In the light of these experiences a deposition
potential of −0.55V was selected.