Abstract
This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine (und-Leu) as the chiral pseudostationary phase in capillary electrophoresis. The effects of using two different counterions (sodium and lysine) on the chiral recognition of binaphthyl derivatives were compared at varying pH conditions. The enantiomeric separation of BNA and BNP enantiomers via capillary electrophoresis, using und-Leu as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium as the counterion. More specifically, at a surfactant concentration of 45 mM, at pH 7, a significant increase in chiral selectivity was observed when lysine was used as the counterion compared to sodium. The enantiomeric resolution of BNA and BNP increased by 6-fold and 1.1-fold, respectively, in capillary electrophoresis experiments when lysine was utilized as the counterion compared to using sodium. Furthermore, the retention factor of BNA and BNP enantiomers also increased approximately 3.5-fold and 4-fold, respectively, in the presence of lysine counterions as compared to using sodium counterions. When running buffer in capillary electrophoresis was increased to pH 11, the resolution and retention factors were nearly identical when comparing the effects of the sodium and lysine counterions. This signifies the important role of lysine’s positive net charge on chiral recognition. This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis.
Highlights
This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine as the chiral pseudostationary phase in capillary electrophoresis
This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis
The chiral recognition of undecanoyl L-leucine (und-Leu) at varying concentrations in the presence of sodium and L-lysine counterions was investigated at pH 7 and 11
Summary
Due to the aforementioned stereospecific reactions that occur within the body, it is not surprising that more than 50% of marketed drugs are chiral [13] [14] [15] [16] These synthesized pharmaceutical drugs, frequently yield racemic mixtures, meaning it contains both enantiomers. It was later determined that while one enantiomer caused the beneficial pharmaceutical effects, the other enantiomer was the cause of the teratogenic effects [17] [18] In response to this tragedy, the Food and Drug Administration has mandated that each enantiomer of a chiral drug be evaluated for its respective physiological effects prior to being marketed [13] [16] [19] [20] [21] [22] [23]. This gave rise to a new scientific challenge: to establish and optimize enantiomeric separation processes and techniques
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