Enantiomeric Separation and Sensitive Detection of Propranolol, Metoprolol and Atenolol Derivatized With a Fluorogenic Reagent, 4-(N-Chloroformylmethyl-N- methyl)amino-7-N,N-dimethylaminosulfonyl-2,1,3- benzoxadiazole (DBD-COCl), on Cellulose Chiral Columns in the Reversed-phase Mode
An electrophilic fluorogenic reagent, 4-(N- chloroformylmethyl-N-methyl)amino-7-N,N- dimethylaminosulfonyl-2,1,3-benzoxadiazole (DBD-COCl), was used to react with three β-blockers, propranolol, metoprolol and atenolol, to yield the derivatives which were subsequently verified to be amide compounds (1:1 adducts) derived from the reaction with the secondary amino group of the β-blockers. DBD-COCl exhibited high reactivity for the reaction completed within 5 min under mild conditions and without any need for a catalyst. The derivatives were well separated enantiomerically on cellulose CSPs (the derivative of propranolol on a Chiralcel OD-R column and those of metoprolol and atenolol on a Chiralcel OJ-R column) in the reversed-phase mode, with the S-configurations being eluted before the R-configurations. The derivatives were stable at 4°C for 1 week. The detection limits (S/N = 3) were 50 fmol for both (S)- and (R)-propranolol, 12 and 17 fmol for (S)- and (R)-metoprolol, respectively, and 15 and 20 fmol for (S)- and (R)-atenolol, respectively.