Analyte: Sodium nitrate (ICP grade) (as sodium), CAS Number: 7631-99-4; Analyte: Magnesium nitrate hexahydrate (ICP grade) (as magnesium, CAS Number: 13446-18-9; Analyte: Potassium nitrate (ICP grade) (as potassium), CAS Number: 7757-79-1; Analyte: Calcium carbonate (ICP grade) (as calcium), CAS Number: 471-34-1 . EPA, Method: 200.7 Rev 3.3; EPA, Method: 200.7 Rev 4.4.