All of the following are techniques of protein purification and separation, EXCEPT:

Purified proteins can be obtained by several methods: gel-filtration chromatography, ion-exchange chromatography, immunoaffinity chromatography, immunoprecipitation, and salt precipitation. New methods are, micropreparative electrophoresis, and centrifugation. Ref: Harper's Illustrated Biochemistry 27th Edition, Page 21-24; The Protein Protocols Handbook edited by John M. Walker, 1996, Page 215.