TABLE OF CONTENTS This technique is often referred to under several headings such as gel filtration, gel permeation, or size exclusion chromatography. In its simplest form, gel filtration, it is often used to desalt solutions and is regularly used to compliment ion exchange separations. In more complex separations it can be used to separate proteins of different size or shape. This mode of separation is rarely performed at high pressure and is often reserved for separating mixtures, as the title suggests, by taking advantage of the differing size.
Why discuss this approach if it is limited to low pressure operation? The ongoing and future development of recombinant processes for the preparation of biopharmaceuticals will require a concurrent high performance approach to separation of proteins from fermentation broths and from salts. The productivity of current approaches using low pressure systems or ultrafiltration will be insufficient to cope with the long-term demand. It is inevitable that manufacturers will develop high performance techniques and high pressure packing media. It is possible to envisage the use of continuous techniques such as SMB chromatography in size exclusion mode [3.15].
The column packing media used in size exclusion chromatography is available in various pore sizes, designed to exclude larger molecules. For simple desalting of a protein the separation works by excluding the biological macromolecule from the pores of the packing media and allowing the salt to penetrate the pores, delaying its elution. Clearly the protein is not retained and simply follows the path of convectional...
