| Reference standard | CAS No. |
|---|---|
| Digitoxin (Impurity A) | 71-63-6 |
| Gitoxin (Impurity B) | 4562-36-1 |
| Digoxigenin (Impurity C) | 1672-46-4 |
| Diginatin (Impurity E) | 52589-12-5 |
| Neodigoxin (Impurity G) | 55576-67-5 |
| Lanatoside C (Impurity H) | 17575-22-3 |
| Digoxigenin tetrakisdigitoxoside (Impurity K) | 31539-05-6 |