All samples were coated with a layer of approximately 5 nm of carbon before WDX measurement to avoid charging effects under the electron beam. In order to minimize beam damage of the sensitive Na2O-P2O5-AlF3-SO3 glasses the count rate of the elements in question was initially recorded as a function of beam time, and the excitation conditions were optimized accordingly. As a result, the energy of the exciting electron was set to E0 = 10 kV, and a moderate beam current of 30 nA was applied. The beam diameter was defocused to 100 µm.