We explained a simple method of determining the molecular weight of a pure glycoside. The method wag based on the law that when glycosides were mixed with alkali metal ions, only the adduct ions of molecule with alkali metal ions appeard in the high mass region of their Fast Atom Bombardment mass spectra. In the same way, when a mixture of glycosides was mixed with an appropriate amount of Na+ and Li+, pairs of strong peaks appeared in the FAB mass spectra. These adduct ions were easily recognized due to the fact that they were very strong and their mass difference was uniue (16u). From these adducts ions, the molecular weight of each glycoside in the mixture may be determined. This technique has not been reported previously.
