Metoprolol Impurity M DiHCl 1,3-Bis[(1-Methylethyl)aMino]-2-propanol Dihydrochloride 2-Hydroxy-N,N'-diisopropylpropane-1,3-diaminium dichloride 1,3-bis(isopropylamino)propan-2-ol dihydrochloride Metoprolol Impurity 10(Metoprolol EP Impurity M) Metoprolol impurity 10/Metoprolol EP Impurity M DiHCl/1,3-Bis[(1-methylethyl)amino]-2-propanol Dihydrochloride Metoprolol-10 1,3-Bis[(1-methylethyl)amino]propan