ENANTIOSEPARATION OF BETA-BLOCKERS LABELED WITH A CHIRAL FLUORESCENT REAGENT, R(-)-DBD-PYNCS, BY REVERSED-PHASE LIQUID-CHROMATOGRAPHY

A fluorescent chiral tagging reagent, 7-(N,N-dimethylaminosulfonyl)-2, 1,3-benzoxadiazole [R(-)-DBD-PyNCS], has been used for the liquid chro matographic resolution of racemic pairs of beta-blockers. The reagent reacts with beta-blockers at 65 degrees C for 90 min in aqueous aceton itrile containing 0.05% triethylamine to produce the corresponding pai r of diastereomers. No racemization occurs during the lagging reaction under these conditions. From results of the time-course study of oxpr enolol the reactivities of the enantiomers of beta-blockers with R(-)- DBD-PyNCS are comparable. The optimum excitation and emission waveleng ths of the resulting derivatives were ca. 460 and 550 nm, respectively . The derivatives of beta-blockers were efficiently resolved by a reve rsed-phase column with water-acetonitrile containing 0.1% trifluoroace tic acid as the eluent. The resolution (Rs) values of the diastereomer s derived from 10 beta-blockers were in the range of 1.54-4.80. The Rs value for timolol was 0.643. The detection limits (signal-to-noise ra tio of 2) were one or two orders of magnitude lower with beta-blockers having the iso-propylamino structure (15-300 fmol) than with those ha ving the tert-butylamino structure (1.25-8.00 pmol). The proposed proc edure was applied to the determination of R(+)- and S(-)-propranolol i n rat plasma and saliva after oral administration of R(+)-propranolol hydrochloride or S(-)-propranolol hydrochloride. (C) 1997 Elsevier Sci ence B.V.