Affinity liquid chromatography method for the quantification of immunoglobulin G in bovine colostrum powders

An affinity liquid chromatography (LC) method for the determination of bovine immunoglobulin G (IgG), using protein G coupled to an agarose support, was modified to permit the quantification of IgG in colostrum-based powders. Sample preparation included pH adjustment to 4.6 to precipitate casein and denatured whey protein. The method was applied to a range of colostrum powders and was compared with the alternative independent methods of surface plasmon resonance immunoassay, radial immunodiffusion, and reversed-phase LC. The method was rapid, and performance parameters included a working range of 10-150 microg IgG and precision relative standard deviation values of <10%.