Omeprazole Impurity: 5-Methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1-methyl-1H-benzimidazole + 6-Methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1-methyl-1H-benzimidazole (N-Methyl Omeprazole mixture of isomers).