Abstract: Methods, apparatuses, and kits for fractionating complex mixtures of biological molecules are provided. In one aspect the methods provided include providing a series of different sorbents, introducing the complex mixture to the series of sorbents, contacting serially the complex mixture with each of the sorbents, and capturing biomolecular components from the complex mixture on the sorbents so that each of the sorbents captures a substantially unique subset of said plurality of biomolecular components.

Abstract: Proteins can be separated from mixtures, based on their pI values, through the use of a series of chromatographic materials, each comprising a solid buffer and an ion exchange resin. Each solid buffer generates a stable pH, such that passing proteins possess a net charge and can be separated by means of an appropriate ion exchanger. In this fashion, proteins from complex biological fluids can be separated for identification and study.