High performance liquid chromatographic determination of lactose in milk

A rapid and simple high performance liquid chromatographic method for the determination of lactose in milk was developed. Samples were diluted with 0.5% perchloric acid and centrifuged, and an aliquot of the supernate was mixed with acetonitrile. Lactose was separated on a 10 micron particle-size silica column with aqueous acetonitrile as the mobile phase. The recovery of lactose from whole, skim, and chocolate milk averaged 99.2, 101.1, and 100.4%, respectively. Coefficients of variation for routinely performed duplicate determinations are between 1.0 and 1.5%.