Determination of optical purity by nonenantioselective LC using CD detection

The use of a circular dichroism (CD) based HPLC detection system was recent ly described by some authors and proposed for a nonenantioselective HPLC en antiomeric purity determination. Indeed the system, measuring both CD and U V signals simultaneously, allows the evaluation of the g anisotropy factor. In order to experimentally support such an analytical procedure as an alte rnative to the enantioselective chromatographic method currently found in s ome pharmacopocial monographs, we have studied its application to the analy sis of dexchlorpheniramine maleate, an active substance which exhibits a po or CD signal in the 250-270 nm spectral region with a g value of the order of 10(-4). The results reported indicate that the suitability of the studie d procedure for the enantiomeric purity determination is obtained only when the CD-detector reaches high stability, indeed a certain time lag is syste matically necessary to obtain stable responses, i.e. adequate precision. Th e enantioselective HPLC procedure seems to be more precise for enantiomeric purity values less than or equal to2% than the CD based detection system; such a disadvantage might be counterbalanced by the use of non chiral stati onary phases. (C) 2001 Elsevier Science B.V. All rights reserved.