The influence of diamine counterion use and surfactant counterion ratio on chiral selectivity of amino acid-based surfactants

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, 1−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑦𝑙−2, 2−𝑑𝑖𝑦𝑙ℎ𝑦𝑑𝑟𝑜𝑔𝑒𝑛(𝐵𝑁 𝑃 )1, 1′−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑦𝑙−2, 2′−𝑑𝑖𝑎𝑚𝑖𝑛𝑒(𝐵𝑁𝐴)𝑎𝑛𝑑1, 1′−𝑏𝑖−2−𝑛𝑎𝑝ℎ𝑡ℎ𝑜𝑙(𝐵𝑂𝐻

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.