(S)-3-(cyanodiphenylmethyl)-1,1-bis(2-(2,3-dihydrobenzofuran-5-yl)ethyl)pyrrolidin-1-ium bromide,(3S)-3-(cyanodiphenylmethyl)-1,1-bis[2-(2,3-dihydro-1-benzofuran-5-yl)ethyl]pyrrolidin-1-ium bromide,Impurity in commercial preparations of Darifenacin.,Darifenacin Impurity