Afatinib Impurity A Catalogue A155361 CAS 314771-88-5 M.W 404.78 M.F C18H14ClFN4O4 Specifications FAQs (S)-N-(3-chloro-4-fluorophenyl)-6-nitro-7-((tetrahydrofuran-3-yl)oxy)quinazolin-4-amine