Separation of nadolol stereoisomers by chiral liquid chromatography at analytical and preparative scales

The separation of the four nadolol stereoisomers on Chiralpak® AD by chiral liquid chromatography was carried out at both analytical and preparative scales. A screening of possible mobile-phase compositions was performed using different alcohol-hydrocarbon mixtures. The results obtained confirm the use of 20:80:0.3 ethanol-hexane-diethylamine reported by McCarthy (1994) but introduce other possibilities for the complete resolution of the four nadolol stereoisomers at analytical scale, namely, the mixtures 30-40:70-60:0.3 ethanol-heptane-diethylamine. Additionally, this work describes how retention and resolution depend on the ethanol content in hexane and heptane mixtures. The separation of nadolol stereoisomers is also carried out at preparative scale and different alcohol-hydrocarbon compositions are proposed, depending on the target component to be obtained. Particularly, this work presents the experimental separation of the more retained nadolol stereoisomer (RSR-nadolol) by simulated moving bed (SMB) chromatography using an 80:20:0.3 ethanol-heptane-diethylamine mobile phase. For a 2 g/l feed concentration, RSR-nadolol is 100% recovered at the extract outlet stream, 100% pure, and with a system productivity of 0.65 g(RSR-nadolol)/(l(bed)(.)h) and a solvent consumption of 9.6 l(solvent)/g(RSR-nadolol).