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 prederivatization 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.

Rapid, specific method for diethylstilbestrol analysis using an in-line photochemical reactor with high-performance liquid chromatography and fluorescence detection.

Low ppb levels of diethylstilbestrol in biological samples of human and animal origin can be determined using a unique in-line separation-photoreaction-fluorescence detection analytical system. After a very simple extraction procedure, the diethylstilbestrol is separated from interfering substances by high-performance liquid chromatography, photoconverted to a fluorescent product, and detected by fluorescence spectroscopy at optimised excitation-emission wavelengths. A sample can be extracted and analysed in less than 1 h.