Enantiomeric purity determination of propranolol by cyclodextrin-modified capillary electrophoresis

Abstract

A capillary electrophoretic method for the enantiomeric purity determination of either enantiomer of propranolol was developed using cyclodextrins as chiral additives and uncoated fused-silica capillaries thermostated at 15°C. The effect of the type and concentration of cyclodextrin added to a triethanolamine-phosphate buffer (pH 3.0) on chiral resolution and migration times was studied. The propranolol enantiomers could be separated with all cyclodextrins tested (β-cyclodextrin and seven of its derivatives), except dimethyl-β-cyclodextrin. A particularly high resolution value of 4.4 was obtained for propranolol enantiomers with a buffer containing 10 m M carboxymethyl-β-cyclodextrin. This buffer was selected for testing the enantiomeric purity of propranolol, making it possible to reach detection limits of less than 0.1% for the minor enantiomer. The R enantiomer of propranolol (second migrating) could be quantified at the 0.5% level with good precision (intra-day R.S.D. = 1.7%) in samples of the S enatiomer (first migrating), while the limit of quantification of the latter, when present as an impurity in the R enantiomer, was 0.1%. The method also gave good results in terms of linearity and accuracy.