Standards for X-ray Fluorescence Spectroscopy These standards are supplied as ¼” (33mm) diameter pressed pellets or metal foils, and are prepared from selected high purity elements and compounds to ensure interference free-spectra. They are suitable for use by experienced spectroscopists as well as staff training. Each of the pressed pellets is supported by a thin-walled aluminum cup which is protected from damage during handling and minimizes the risk of touching the standard materials (some of which are harmful). The precious metal foils are approximately 0.125mm thick and are stretched across plastic supports. Standards are available for 60 elements.