Charged and uncharged cyclodextrins as chiral selectors in capillary electrophoresis

Chiral separation by chromatographic and electromigration techniques. A Review

“…The authors have shown that neutral, basic, zwitterionic and even acidic enantiomers can be separated. Carboxyl functional CDs such as carboxymethyl-b-CD (CM-b-CD) [355] carboxyethyl-b-CD (CE-b-CD) [355] and succinyl-b-CD [355,356] found application to a broad spectrum of neutral and basic compounds [13,15,16]. Phosphated CDs [357,358] are another group of negatively charged CDs successfully applied to the separation of some drug enantiomers.…”

Captisol® as Chiral Selector in Capillary Electrophoresis of Non-Acidic Drugs

“…To find the suitable conditions for the chiral separation of the model molecules, a series of preliminary experiments were conducted with different buffer compositions at different pH values, in order to characterize the electrophoretic behavior of the analytes in an achiral system over a wide adjustable pH range (2)(3)(4)(5)(6)(7)(8)(9)(10)(11). In the preliminary analysis we used: 25 mM phosphoric acid (pH -2.1), 25 mM sodium didydrogenophosphate (pH -5.0), 25 mM disodium hydrogenophosphate -sodium didydrogenophosphate (1:1) (pH -7.0) and 25 mM sodium tetraborate (pH -9.3) BGEs respectively and we modified the pH of the buffer by adding a 0.1M sodium hydroxide solution.…”

“…The stability of the formed complex is influenced by several parameters, including chemical structure and hydrophobicity of the analyte, CD type and concentration, background electrolyte (BGE) composition, buffer pH and temperature. 5,6 The utility of native CDs as chiral additives is sometimes limited, and therefore a large number of derivatized CDs have been developed and introduced as chiral selectors. By derivatization, hydrophobicity and charge can be altered and affect, electrophoretic mobility or complexing ability of the analytes.…”

“…Further advantages of charged CD derivatives are related to the better solubility and the ability to display additional electrostatic interactions. 5,7,8 Captisol® is a particular type of sulfobutyl ether derivative of β-CD with a range of six to seven sulfobutyl ether groups per CD molecule ( figure 1). Because of the very low pKa of the sulfonic acid groups, Captisol® carries multiple negative charges at physiologically compatible pH values.…”

Advances in capillary electrophoresis

“…In particular, methylated and hydroxypropylated cyclodextrins have shown high selectivity to various racemates [162,163]. Several anionic cyclodextrins such as sulfobutylether b-cyclodextrin and b-cyclodextrin phosphate showed high enantioselectivity to numerous basic racemates as compared to natural species [164][165][166]. Such b-cyclodextrin derivatives are particularly successful in separating cationic analytes owing not only to the electrostatic interaction between the oppositely charged chiral selector and the solutes, but also owing to the large difference in the electrophoretic mobilities between free and complexed analytes.…”