Determination of Lactose in Milk Products by High-Performance Liquid Chromatography

Abstract

A method to determine lactose in dairy products by high-performance liquid chromatography is described. Samples suitable for assay were prepared from the liquid state by deproteinization with trichloroacetic acid (6% wt/vol, final concentration). Lactose was separated by injection of the deproteinized sample onto a .mu.Bondapak/Carbohydrate column and isocratic elution with an acetonitrile/water mobile phase. Detection was with a differential refractometer. Sequential injection of a lactose standard and sample, addition of a standard quantity of lactose to the sample, and addition of an internal standard (xylose) to the sample were techniques for quantitation. The validity of high-performance liquid chromatography as a method for determining lactose concentration in milk products was supported by recovery experiments and comparison of results with those by a phenol-sulfuric acid, colorimetric assay.