Is a complex formed by two or more different ligands (reagents) and the same metal ion. Due to the synergistic effect of different ligands, the complexed complexes show good analytical chemistry in terms of selectivity, stability, color development and solvent extraction. As the formation of mixed complexes with universal, widely used in analytical chemistry.
Heteropoly polynuclear complexes refer to complexes formed by the participation of two or more different metal ions such as Ce-tartaric acid-Eu, Cu-citric acid-Cr, La-bromopyrogallol red-Y, Sc- Arsenazo Ⅲ-Mo belong to this category. This is a new field developed by co-extraction, total coloration and co-concealment. Such complexes not only have theoretical significance but also have practical value. The above system has been applied in practical work.