I am in the process of developing an EPA 200.8 based method to run Ca, Mg, K, Fe, Na, and Zn on the Perkin Elmer Elan 9000 ICP-MS. I wanted to see if anyone knew how concentrated I can make my standards before the linear range starts to degrade. The other day I went up to 20 mg/l without any problems. Any help is appreciated. Thank you.