Atorvastatin calcium trihydrate Impurity: (3R,5R)-Ethyl-7-[2-(4-fluorophenyl)-5-(1-methylethyl)-3-phenyl-4-(phenylcarbamoyl)-1H-pyrrol-1-yl]-3,5-dihydroxyheptanoic acid)-1H-pyrrol-1-yl]-3,5-dihydroxyheptanoic acid.