Sitagliptin Ketoamide Impurity

Sildenafil Impurity B ; Sildenafil N-Oxide ;5-[2-Ethoxy-5-[(4-methyl-4-oxido-1-piperazinyl)sulfonyl]phenyl]-1, 6-dihydro-1-methyl-3-propyl-7H-pyrazolo[4, 3-d]pyrimidin-7-one ;