Enantiomeric separation of salbutamol and related impurities using capillary electrophoresis

The enantiomeric resolution of salbutamol and its chiral and achiral related impurities is investigated using capillary electrophoresis. The effects of nine varieties of cyclodextrin, cyclodextrin concentration and organic modifier concentration were studied in an attempt to resolve all possible analytes in a complex mixture of salbutamol-related solutes. Eleven components including three enantiomeric pairs were baseline resolved using 112 mM dimethyl-beta-cyclodextrin at pH 2.5 in a citric acid/phosphate buffer. Both methanol and iso-propyl alcohol at up to 20% were found to have a deleterious effect on the separation. Binding constants and mobility values for the free and complexed forms for each solute were determined. The results are interpreted by considering the physical properties of the molecules under the conditions employed and a rationale proposed for the underlying basis for chiral and achiral selectivity.