Hexavalent Chromium (Cr +6)

1,2,3,7,8,9-Hexachloro[13C12]dibenzo-p-dioxin, 1.2ml x 50ug/ml, toluene

2,3,4,5,6-Pentachlorophenol-13C6

2,2',3,4,4',6-Hexabromodiphenyl ether, 1.2ml x 50ug/ml, nonane