3.2. Optimization of the electrode modification
The dependence of SIAeSWASV responses for Pb2þ and Cd2þ on
the concentration of the Nafion solution added to the modified
carbon ink was studied in the range of 0.2e2.5 wt %. The stripping
peak currents of both Pb2þ and Cd2þ ions initially increased as the
Nafion concentration increased from 0.2 to 0.5 wt % but then
decreased at higher Nafion concentrations (Fig. 2A). This
phenomenon can be explained by the fact that high concentrations
of the Nafion polymer can cause more complicated complexations
leading to a decline in the current intensity. Therefore, a 0.5 wt %
Nafion concentration was selected for further work.
When the amount of the D24C8 crown ether as ionophore was
varied from 5 to 30 mg, while the Nafion concentration was kept
constant (0.5 wt %), the stripping response for both Pb2þ and Cd2þ
was enhanced as the D24C8 content in the modified electrode
increased up to 10 mg (Fig. 2B), due to the increased number of
active sites to transfer metal ions from the solution to the electrode