ISSN:
1612-1112
Keywords:
Capillary electrophoresis
;
Chiral separation
;
Leucovorin 5-methyl-tetrahydrofolate
;
Cyclodextrin, binding constants
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary Capillary electrophoresis with an electrolyte containing cyclodextrin was investigated for the simultaneous separation of the diastereoisomers of 6R,S-leucovorin and its active metabolite 6R,S-5-methyl-tetrahydrofolate. α, β and γ-cyclodextrin separated the diastereoisomers of 5-methyl-tetrahydrofolate, while only γ-cyclodextrin was found to be effective for the chiral separation of leucovorin. The effect of γ-cyclodextrin concentration was investigated, and subsequently a curve-fitting analysis for the quantitative estimation of the binding constants was attempted. The binding constants were found to be very small, in the range 2–4 M−1. Although the interaction between γ-cyclodextrin and the tetrahydrofolates is weak, the high efficiency of capillary electrophoresis and the use of high concentrations of γ-cyclodextrin allow baseline chiral separation of the diastereoisomers of leucovorin and 5-methyl-tetrahydrofolate. Changes in temperature exert differing effects on the separations of leucovorin and 5-methyl-tetrahydrofolate; higher temperatures improved the separation of leucovorin diastereoisomers but reduced the resolution of 5-methyl-tetrahydrofolate diastereoisomers. The effects of urea and buffer salt concentrations and of buffer pH were also investigated. Capillary electrophoresis with γ-cyclodextrin was used to analyse plasma samples spiked with clinically-relevant levels of leucovorin and 5-methyl-tetrahydrofolate. Resolution of these compounds in ultrafiltered plasma was demonstrated, but detection sensitivity was not adequate for the routine use of this method for the determination of leucovorin and 5-methyl-tetrahydrofolate in plasma. In addition, a simple technique to reverse the elution order of ionic stereoisomers was demonstrated. By adding a cationic surfactant into the buffer and reversing the separation potential, the elution order of the diastereoisomers of leucovorin and 5-methyl-tetrahydrofolate was reversed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02278596
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