Determining eight colorants in milk beverages by capillary electrophoresis

Milk beverages are popular because of their high nutritional value, and milk products that are enhanced with various fruit flavors are especially in high demand in Asia. Colorants are usually added to fruit flavored milk in order to increase its attraction and appearance, therefore, the detection and measurement of colorants in this type of beverage are relatively important for health issue reasons. Carminic acid, a natural colorant, along with tartrazine, Fast green FCF, Brilliant blue FCF, Allura Red AC, Indigo carmine, Sunset yellow FCF, and New coccine, which are seven different synthetic food colorants, are commonly used as food additives, therefore, this study would focus on the development of an analytical method for the detection of these common colorants in milk beverages. A high efficiency capillary electrophoresis separation method was finished by a pH 10.0 running buffer containing 7.0 mM β-cyclodextrin, and the eight colorants were separated with baseline resolution within 9 min. In order to reduce the matrix interference resulting from the constituents of milk, a suitable polyamide column solid-phase extraction (SPE) was also investigated for milk sample pretreatment. The combination of the simple SPE pretreatment and the fast separation method of capillary electrophoresis, was able to determine successfully without matrix interference the content of these colorant additives in commercial milk beverages. The recoveries of the eight food colorants in milk beverages were better than 85% and the detection limits were also lower than 0.5 μg/ml by the developed method.