The influence of the substituent position in monocarboxymethyl-gamma-cyclodextrins on enantioselectivity in capillary electrophoresis
Abstract
Three newly synthesized chiral selectors, namely, 2(I)-O-, 3(I)-O-, and 6(I)-O-carboxymethyl--cyclodextrin, native -cyclodextrin, and commercially available carboxymethylated -cyclodextrin with degree of substitution of 3-6 were used as additives in a background electrolyte composed of phosphate buffer at 20mmol/L concentration and pH 2.5. This system was used for the analysis of several biologically significant low-molecular-mass chiral compounds by capillary electrophoresis.
The results confirmed that the position of carboxymethyl group influences the enantioseparation efficiency of all the studied analytes. The 2(I)-O- and 3(I)-O- regioisomers provide a significantly better resolution than native -cyclodextrin, while the 6(I)-O-regioisomer gives only a slightly better enantioseparation than native -cyclodextrin.
The application of -cyclodextrin possessing higher number of carboxymethyl groups led to the best resolution for the majority of the compounds analyzed.