Figure 1. Effect of pH on copper ion extraction. Conditions: 15 mL of 0.2 µ g mL -1 Cu 2+ ion at various pH values, 0.06 (w/v) Triton X-114, 1.5 mM DFID, 0.5% (w/v) NaCl, eluting solution 0.5 mL of 0.5 M HNO in methanol. 3