The influence of diamine counterion use and surfactant counterion ratio on chiral selectivity of amino acid-based surfactants
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Abstract
In this study, the effects of counterion type and surfactant-to-counterion ratio on the chiral selectivity of several binaphthyl derivatives with L,L- undecanoyl leucine-valinate was examined by use of Micellar Electrokinetic Chromatography (MEKC). The chiral separations of 1, 1โ๐๐โ2โ๐๐๐โ๐กโ๐ฆ๐โ2, 2โ๐๐๐ฆ๐โ๐ฆ๐๐๐๐๐๐(๐ต๐ ๐ )1, 1โฒโ๐๐โ2โ๐๐๐โ๐กโ๐ฆ๐โ2, 2โฒโ๐๐๐๐๐๐๐(๐ต๐๐ด)๐๐๐1, 1โฒโ๐๐โ2โ๐๐๐โ๐กโ๐๐(๐ต๐๐ป
by the dipeptide surfactant varied widely in the presence of three counterions, 1,2 diaminoethyl, 1,2 diamino- propyl, and 1,3 diaminopropyl and with surfactant-to-counterion ratios of 1-to-1 and 1-to-0.5. The results of this study have shown that the selection of 1,2 diaminoethyl in a 1-to-1 surfactant-counterion-ratio provides enhanced baseline separation for enantiomers of BOH in comparison to its 1-to-0.5 counterpart, though no significant difference in separation can be observed for enantiomers of BNP under the same conditions. Despite the observation that every one of the three included counterions engendered some degree of separation for each analyte, enantiomers of BNP exhibited heightened separation in the presence of 1,2 diaminoethyl and 1,2 diaminopropyl at a pH level of 8. Conversely, the comparative Na counterion separates enantiomers of BOH and BNA significantly better than the counterions examined.