A 0.2500 g sample of dried plant material is predigest for 60 minutes with 2 mL H2O2 and 0.5 mL HNO3. Each sample is then digested in the microwave using modified Miller Digest method: 100oC for 8 minutes followed by 195oC for 12 minutes. Analysis of digestate for Al, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Si, Sr, Ti, V and Zn by ICP-OES.
(See Method References No. 59 and No. 21)