Ion exchange chromatography can be subdivided into cation exchange chromatography, in which positively charged ions bind to a negatively charged resin; and anion exchange chromatography, in which the binding ions are negative, and the immobilized functional group is positive. Once the solutes are bound, the column is washed to equilibrate it in your starting buffer, which should be of low ionic strength, and then the bound molecules are eluted off using a gradient of a second buffer which steadily increases the ionic strength of the eluent solution.
Alternatively, the pH of the eluent buffer can be modified as to give your protein or the matrix a charge at which they will not interact and your molecule of interest elutes from the resin. In the study of LU Rong-Rong, et al. lactoferrin was extracted from bovine colostrums using ion exchange chromatography by SP Sepharose Fast Flow (SP Sepharose FF) of excellent absorption specialty for LF, was chosen as the ion exchange with elution rate of 2 L/h. 0. mol/L NaCl aqueous solution was used to elute the secretory immunoglobulin A and lactoperoxidase. Then, lactoferrin was eluted with 1. 0 mol/L NaCl aqueous buffer. Lactoferrin fraction is shown as a single band in SDS-PAGE with molecular weight of 80400 Da. The isoelectric point of lactoferrin is 8. 65 determined by isoelectric focusing. The purity of refined LF on pilot production is 94. 20% with a yield of 75. 45%. Reference: Retrieve from: http://124. 205. 222. 100/Jwk_spkx/EN/abstract/abstract14803. shtml