Certified Reference Material (CRM).

20000 mg/L K, 1000 mg/L each of As, Pb, Tl, 500 mg/L Se, 300 mg/L each of Ag, Ba, Cd, Co, Cr, Cu, Ni, V, Zn, 200 mg/L Mn, 100 mg/L each of Be, Hg in HNO₃ 5%