Dual CD system in capillary electrophoresis for direct separation of the four stereoisomers of agonist and antagonist melatoninergic ligands

Abstract

In this study, baseline separation of the stereoisomers of six tetrahydronaphthalenic derivatives (agonists and antagonists for the melatonin (N-acetyl-5-methoxytryptamin) binding sites) was successfully achieved using CE and CDs as chiral selectors. The method for the simultaneous chiral separation of the four stereoisomers uses a capillary dynamically coated with polyethylene oxide and a dual CD system. Optimisation was performed first upon the constituents of the CD system, by varying neutral and anionic CD type, size and concentration, at first in mono-CD systems and subsequently in dual neutral/anionic CD systems. Once these characteristics of the dual CD system were established, operational parameters such as voltage and temperature were then optimised. Under the optimal conditions (i.e. 1.5% w/v of highly S-beta-CD and 10 mM of gamma-CD in 25 mM phosphate buffer (pH 2.5) as the BGE, separation voltage 20 kV and a temperature of 25 degrees C), complete resolution of the six molecules was accomplished. Preliminary results for repeatability and the migration order of the optimised method are described.

Study of the enantioseparation capability of chiral dual system based on chondroitin sulfate C in CE

“…The results obtained from the present polysaccharides‐based dual systems indicated that both of the neutral and anionic polysaccharide selectors contributed to the enantiorecognition (see Table ), similar to the effective dual CDs systems consisting of a neutral and a charged CD in previous papers . It is well known that polysaccharides have a number of stereogenic centers and functional groups, allowing them to have multiple interactions with enantiomers.…”

“…With two different chiral selectors introduced simultaneously, chiral dual system often leads to a significant enhancement of selectivity and resolution (synergistic effect) due to differences in the complexation mechanisms of the two selectors with the analyte enantiomers . The use of dual CD systems has been reported in some studies, in which different combinations of charged and neutral CDs are employed .…”

Analytical and Preparative Chiral Separation of β-Carboline Derivatives, LDL Oxidation Inhibitors, Using HPLC and CE Methodologies: Determination of Enantiomeric Purity

“…We also report the optimization of experimental conditions for the enantiomeric separation of all the compounds using negatively charged highly sulfated-CDs which have been shown to be particularly effective as single system [17][18][19][20][21][22] or as dual system [23] for the enantiomeric separation of cationic compounds. To the best of our knowledge, no article dealing with chiral separation of such b-carboline derivatives neither in HPLC nor in CE was reported.…”

Evaluation of the synergistic effect with amino acids for enantioseparation of basic drugs using capillary electrophoresis

“…Over the years, various CSs have been utilized in CE including cyclodextrins (CDs) and their derivatives, chiral crown ethers, chiral surfactants, ligand‐exchange complexes, linear polysaccharides like maltodextrins (MDs), and DNA oligonucleotides, to improve the enantioseparation capability of various classes of analytes . However, to improve the resolution of enantiomers, in some cases, dual systems by a combined use of two chiral reagents/modifiers in the BGE are applied for the chiral separation . Several combinations of the CSs and modifiers were reported until now, including the combinations of a CD and its neutral or ionic derivatives , CD and ionic liquids , CD and glycogen , CD and metal‐amino acid complex and a CD and a chiral surfactant .…”