The effect of concentration of 5-Br-PADAP on the absorbance was evaluated in the range of 0.1 105–2.5 105mol L1.
The results are given in Fig. 2d.
The absorbance of the complex increases with increasing 5-Br-PADAP concentration up to
0.5 105 mol L1.
Then it remains constant at much higher concentrations.
The excessive chromogenic agent could be co-extracted into the organic phase.
Therefore, 2.5 105 mol L15-Br-PADAP was selected as the optimal concentration in present study.