Special possibilities of ion exchange

Heavy metal cations can be separated as chemical complexes with anion exchangers e.g. Fe + forms a stable complex with chloride  

Carbohydrates (and sugar alcohols) can form a complex with calcium and other metal ions if three of their OH groups form a series axial-equatorial-axial  

Therefore calcium-loaded cation exchangers are important stationary phases for the analysis of carbohydrates (see Fig. 12.5). 

Ion chromatography is an important special case of ion exchange and is described in detail in Chapter 14. 

A ligand is a molecule or an ion that can form a relatively stable bond with a metal cation. For example, ethylenediaminetetraacetic acid (EDTA) is a good ligand for many cations. The complex formation arises as a result of gaps in the metal ion electron system, which are then filled by the hgand. 

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