Determination of cow milk in ewe milk and cheese by capillary electrophoresis of the whey protein fractions

Capillary Electrophoresis was successfully applied to detect and determine the percentage of cow milk used in adulteration of ewe milk products. The sepatation of the whey proteins was achieved in an 80mM pH 9.2 borate buffer, the only component of BGE. Determination of the percentage of cow milk was based on the ratio of the corrected peak area of cow beta-lactoglobulin to the corrected peak area of a ewe protein hence eliminating the need of the internal standard. The use of methyl silanized capillaries and of proper washing after every run eliminated wall-adsorption phenomena and allowed good repeatability for migration time (RSD% 0.5) and and for ration of the corrected peak areas (RSD% 3.0). A preconcentration step made possible to detect small quantities of cow milk , up to0.5% in milk mixtures and up to 2% in cheeses.