The pH was the first critical parameter evaluated for Sn(IV)
complex formation effect on extraction procedures in CPE. Separation
and preconcentration of tin with CPE involve previous formation
of a ternary complex, which needs to present sufficient
hydrophobicity to be extracted into the small volume of the surfactant-rich
phase. The pH is a critical factor affecting both the reaction
between metal ions and ion-pairing ligands, and the
extractability of metallic complex into the surfactant-rich phase
CPE of tin species was performed in different buffer solutions such
as Tris/HCl, NH3/NH4Cl, H2PO4
/HPO4
2 and borate. The effect of pH
on the CPE efficiency was studied in the range of pH 5.0–10.0 and
the results were shown in Fig. 1(a). It could be seen that the highest
signal for Sn(IV) were obtained in pH 8.5 Tris/HCl. Also, the effect
of buffer concentration on the analytical signal was studied in
the range of (0.0–0.05) mol L1 concentration in Fig. 1(b), and the
best analytical signal was obtained with using buffer solutions of
0.035 mol L1
. Therefore, buffer concentration of 0.035 mol L1 at
pH 8.5 was used as optimal value for the subsequent studies.