Analyte: Arsenic (III) oxide (ICP grade) (as arsenic), CAS Number: 1327-53-3; Analyte: Selenium (IV) oxide (ICP grade) (as selenium), CAS Number: 7446-08-4; Analyte: Thallium (I) nitrate (ICP grade) (as thallium), CAS Number: 10102-45-1; Analyte: Lead (II) nitrate (ICP grade) (as lead), CAS Number: 10099-74-8 . EPA, Method: 200.7 Rev 3.3; EPA, Method: 200.7 Rev 4.4.