Gas chromatographic determination of galactose in milk : example of a switching valve used for the protection of the capillary column

Galactose, a marker of heat treatment, has been analysed in milk as pentafluorobenzyloxime acetate by gas chromatography with flame ionization detection using a simple switching valve system. The procedure did not entail any pre-derivatization clean-up for lactose elimination from the sample. In a short pre-column, reagent and lactose derivative excess were separated and the galactose and internal standard derivatives were transferred to the analytical column by a four-port valve. Thus, the analytical column was protected from overloading, so avoiding rapid deterioration.