Ion exchange chromatography

Ion exchange chromatography is based on the phenomenon of attraction between opposite charges. The stationary phase is selected such that it has a particular charge and attracts the sample molecules with the opposite charge. The stationary phase is also termed as the ion exchanger. The ion exchanger can be of two types Cation exchanger and anion exchanger. Cation exchanger has a negative charge and attracts positively charged cation, While anion exchanger is positively charged and attracts negatively charged anion. for the separation of proteins it must be checked at which pH the protein is stable. Is protein is stable at pH one unit above isoelectric ph then anion exchange chromatography is preferred as protein will have a negative charge And if the protein is stable at pH one unit below isoelectic pH then cation exchange chromatography is preferred as protein will have a positive charge. Once the protein binds the stationary phase in the column, elution of protein can be done by change in the pH or by changing the ionic strength.