Enantiomeric quantitation without separation of tramadol via laser-based polarimetry
by Edkins, Thomas J.; Fronheiser, M.; Bobbitt II, Donald R.; Mills, J. E.; Rossi, T. M.
Tramadol hydrochloride drug substance is an analgesic which is the racemic compound of an SS/RR enantiomeric pair. Although these enantiomers can be adequately resolved on an enantioselective HPLC column, peaks from the RS/SR diastereomeric impurity interfere with quantitation. While a conventional reversed-phase column separates the diastereomers, it does not resolve each enantiomer of the two enantiomeric pairs. Using laser-based polarimetric detection with the conventional HPLC separation, enantiomeric quantitation without separation is achieved. This technique is applied to the determination of enantiomeric enrichment in complex mixtures containing all four configurational isomers of tramadol. Plots of peak area response versus % enantiomeric excess (%ee) has provided correlation coefficients of >0.9959, with detection limits as low as 0.4%ee. The limiting factors in %ee determination by this technique will be explored. This technique provides a fast method for determining enantiomeric enrichment when enantioselective chromatography is not practical.
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