Complexing or competing ion:

Generally speaking, liquid ion exchange involves the selective transfer of a solute, an anion or anionic metal complex, from aqueous to organic phase reversibly. The extent of extraction of the metal directly depends on the ease of formation of anionic metal complexes in the aqueous phase. That is to say, aqueous phase parameters like concentration of ligand, hydrogen and metal ion, charge on the complex metal ion involved the presence of other complexing or competing ion and temperature will not only affect the formation of the extractable species but also, in turn, have a significant effect on the extent of extraction. Furthermore, such ion association systems are also sensitive to organic phase parameters like the nature, structure and chain length of the amine, its concentration and the type of the organic solvent used as diluent. Each of these factors can change the course of the overall extraction process of a metallic species unpredictably. It is apparently a general phenomenon that the extraction power of alkylamines increases from primary to secondary to tertiary to quaternary amines. An exception to this rule is the extraction by bulky amines where steric factors generally affect the basicity of amines, which in turn affects the stability and polarity of their salts. Due to steric factors, change in the sequence of extractability of amine salts is also observed in the case of anionic carboxylato complexes.