Estradiol Hemihydrate EP Impurity A Catalogue C206531 CAS 19973-76-3 M.W 270.37 M.F C18H22O2 Specifications FAQs (8R,9S,13S,14S)-3-hydroxy-13-methyl-6,7,8,9,11,12,13,14,15,16-decahydro-17H-cyclopenta[a]phenanthren-17-one