Stereoselective determination of S-naproxen in tablets by capillary electrophoresis

A capillary electrophoresis (CE) method was developed for the stereoselecti ve determination of the non-steroidal anti-inflammatory drug (NSAID), S-nap roxen, in tablets. Several beta-cyclodextrin derivatives (CDs) were tested as chiral selectors, including sulfobutyl-beta-CD (SBCD), carboxymethyl-bet a-CD(CMCD), dimethyl-beta-CD (DMCD) and trimethyl-beta-CD (TMCD), in a phos phoric acid/triethanolamine pH 3 buffer. Under these conditions, the analyt e was mainly present in an uncharged form and therefore, the use a neutral CD(DMCD or TMCD) alone could not lead to enantiomeric separation. On the co ntrary, by addition of a charged CD (SBCD or CMCD) to the running buffer, g iving the analyte enantiomers an adequate mobility, chiral resolution could be achieved, although the resolution values obtained in this case were not quite satisfactory (Rs < 1.5). Dual systems, based on the use of mixtures of charged and neutral CDs, were then investigated. The SBCD/TMCD system wa s found to be particularly well suited to the enantioseparation of naproxen and after optimisation of the concentrations of both CDs, a resolution val ue of 5.4 could be obtained. The method was validated for the determination of R-naproxen (enantiomeric impurity) in the 0.1-2% range, using the racem ic mixture of the analyte. A second validation was performed in the 50-150% range for the quantitation of S-naproxen. In both cases, good results with respect to linearity, precision and accuracy were obtained. (C) 1998 Elsev ier Science B.V. All rights reserved.