Standards, AA, Quality Control Standard 7. Quality Control Standard 21 is a 125mL certified reference material set in a nitric acid matrix for stability. This standard is Traceable to NIST and manufactured in accordance with stringent Quality Assurance guidelines. One year Expiration Date. Contains: Al 100, Ba 100, B 100, K 1000, Si 50, Ag 100, Na 100 ug/mL