INFLUENCE OF THE STRUCTURE OF THE ALCOHOLIC MODIFIER ON THE ENANTIOSELECTIVE SEPARATION OF NADOLOL

The influence of the structure of the alcoholic modifier of the mobile phase on the liquid chromatographic separation of the optical isomers of nadolol on a Pirkle-type chiral stationary phase was investigated. The isomers were separated as their chiral 1-naphthylureides on a col umn consisting of 3,5-dinitrobenzoyl-L-leucine covalently bound to 3-m u m aminopropylsilica, using an eluent consisting of n-hexane modified with an alcohol. A number of straight-chain, branched and unsaturated alcohols with carbon numbers ranging from 1 to 8 were evaluated. The choice of alcohol influenced both retention and selectivity, with opti mum stereoselectivity being observed for C-3. The alcoholic modifiers selectively affected the retention and resolution of the two pairs of enantiomers that constitute nadolol. Thus chromatograms displaying two , three or four peaks could be obtained, depending on which modifier w as employed. The best separation of all four isomers was achieved with ethanol as the modifier.