These standards are supplied as 1/4" (33 mm) 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). X-Ray Fluorescence. Na, Mg, Al, Si, P, S, Cl, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Nb, Sn, Ba, W, and Pb.