Certified elements and grades; Best practice is to order CRM’s that have closer certified elements and grades to the samples being submitted.
Matrix Match; The Matrix matched CRM have similar chemical, mineral and grade characteristics to the samples being tested in the laboratory. CRMs that are made from natural ores, like CDN’s CRMs, and closely match the samples being submitted will mitigate possibility of standards contaminating the actual samples.
Some elements and oxides to consider; Choose CRM’s that have closer chemical and mineral characteristics to your samples.
Consider oxides, sulphides in addition to elements such as sulfur or excess iron, As or Pb
If assaying for gold by fire assay check Pb contents of CDN’s Certified Reference Materials, best practice is to choose standards
with less than %3 Pb.