Influence of methanol on the enantioresolution of antihistamines with carboxymethyl‐β‐cyclodextrin in capillary electrophoresis

Abstract

According to the model of Wren and Rowe, the separation between two enantiomers in capillary electrophoresis (CE) decreases if an organic modifier is added to the run buffer containing a neutral cyclodextrin (CD) in a concentration below its optimal value in a solvent-free system. In previous work, however, it was observed that the addition of methanol to the background electrolyte (BGE) containing not charged carboxymethyl-beta-CD in a concentration below its optimal value, increased the enantioresolution of dimetindene maleate. The enantioresolution decreased when other organic modifiers (ethanol, isopropanol or acetonitrile) were added and/or when other neutral (beta-CD, hydroxypropyl-beta-CD) or chargeable (carboxyethyl-beta- and succinyl-beta-CD) CDs were used. In this CE study further attempts are made to elucidate the observed phenomena through investigating other basic drugs. The effect of organic modifier and CD concentration on the enantioseparation was studied by means of central composite designs. It is shown that obtaining this increase in enantioresolution depends upon the type of CD, the type of organic modifier, and the structure of the analytes. It was also observed that small differences in the structure of the analytes or the CD could have an influence on the enantioresolution. The addition of methanol also resulted in different effects on the resolution of closely related analytes.

(S)-(+)-2-Octanol as a Chiral Oil Core for the Microemulsion Electrokinetic Chromatographic Separation of Chiral Basic Drugs

“…Further elucidation of the complexation process can only be performed with other techniques like, NMR and MS. 25,27 Our observation suggested that the hydrogen-bond interaction between chiral oil, enantiomeric solute, and MeOH additive might be the major chiral recognition mechanism for enantioseparation of the basic drug (±)-norephedrine, by using (S)-(+)-2-octanol as the oil core in the MEEKC system. The microemulsion used in this work exhibited an exceptional stability of at least 2 months.…”

“…Therefore, it could be concluded that the enantioselectivity of the analyte-selector complex can be favorably influenced by MeOH, through an interaction with the complex. 27 There probably existed competition between the solutes and the MeOH additive for binding to the hydrogen bonding site on the chiral oil core in the microemulsion droplet. 28 Several hypotheses to explain the observed variation with MeOH were investigated.…”

“…17,19,23 In addition, it is also recognized that organic modifiers can have an effect on the electroosmotic flow (EOF), the viscosity, the dielectric constant, the conductivity of the background electrolyte, and the solubility of the analytes. 27 Consequently, the effect of the 1-butanol concentration (4.4 to 8.8% (w/w)) on the enantioseparation of (±)-norephedrine was studied; and the obtained results can be seen in Fig. 3(C).…”

Validated capillary electrophoresis assay for the simultaneous enantioselective determination of propafenone and its major metabolites in biological samples

“…Analysis of the mixture however provided incomplete separation between R-PPF and S-5OH-PPF. The use of 0.6% sulfated b-CD together with 15% v/v methanol [27,28] resulted in complete separation of all compounds. For gaining sensitivity, sample injection was increased to 9 psi6s, which in turn decreased the resolution between R-PPF and S-5OH-PPF.…”

Chiral separation of catechin by capillary electrophoresis using mono‐, di‐, tri‐succinyl‐β‐cyclodextrin as chiral selectors

“…[20][21][22][23][24][25][26] However, most of works were conducted using mixed CDs with different DS values. [20][21][22][23][24][25] In the present work, we used synthesized Suc-bCDs with defined DS values such as one, two, or three of succinyl substituents as chiral selectors for the separation of (6)-catechin in CE. The effect of selector with different DS values, selector concentration, pH, and buffer concentration along with the influence of methanol on the separation of (6)-catechin were investigated.…”