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Simultaneous determination of dopa and carbidopa enantiomers by capillary zone electrophoresis
Author(s) -
Ha Pham Thi Thanh,
Van Schepdael Ann,
Hautaaho Tuula,
Roets Eugene,
Hoogmartens Jos
Publication year - 2002
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/1522-2683(200210)23:19<3404::aid-elps3404>3.0.co;2-x
Subject(s) - enantiomer , carbidopa , detection limit , cyclodextrin , analyte , chemistry , chromatography , sulfation , resolution (logic) , stereochemistry , levodopa , computer science , medicine , biochemistry , disease , pathology , artificial intelligence , parkinson's disease
Dopa and carbidopa, components of the dual therapy for Parkinson's disease treatment, are both provided as single enantiomers, since their D ‐forms are inactive. To ensure the efficiency and safety of the therapy, these D ‐enantiomers, therefore, should be considered as impurities. In this paper, the enantioseparation power of different types of cyclodextrins, both neutral and charged ones, on dopa and carbidopa enantiomers was tested. Three methods of simultaneous separation of dopa and carbidopa enantiomers were developed, using highly sulfated β‐cyclodextrin and sulfated β‐cyclodextrin as chiral selector, in normal and reversed polarity mode. Two methods among these three were found sensitive enough for the quantitation of 0.1% D ‐enantiomers in L ‐forms (impurity level). After the optimization study, the best method was selected, using 16 m M sulfated β‐cyclodextrin in 15 m M sodium phosphate buffer pH 2.45, an uncoated fused‐silica capillary (50 νm inner diameter, 30 cm total length), and an applied voltage of −12 kV. This method is robust and efficient, with very high resolution for all peaks within a short analysis time of 10 min. Quantitatively, the method offers a limit of detection (LOD) of 0.2 νg/mL and a limit of quantitation (LOQ) of 0.5 νg/mL for both D ‐dopa and D ‐carbidopa, which is equivalent to 0.02% and 0.05% against the respective L ‐enantiomers. A linear relationship was found between the concentration of the analyte and the corresponding peak area in a range of 0.5–2.0 νg/mL.