A comparison of phosphated and sulfated β-cyclodextrins as chiral selectors for capillary electrophoresis (original) (raw)
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Fresenius' journal of analytical chemistry, 2001
The enantioseparation capabilities of three different functionalized beta-cyclodextrins, two sulfated beta-cyclodextrins with 4 and 15 nominal degrees of substitution and a phosphated beta-cyclodextrin with 8 degrees of substitution, were compared. While anodic detection was used with both sulfated cyclodextrins, the phosphated cyclodextrin required cathodic detection suggesting either lower ionization of the phosphated cyclodextrin or generally lower affinity of the analytes for the phosphated cyclodextrin. The effects of several experimental parameters were evaluated with respect to enantioseparation. The degrees of substitution of the cyclodextrin, pH of the background electrolyte as well as the concentration of the functionalized beta-cyclodextrin, each had a significant influence on the successful enantiomeric separation of the chiral drugs investigated.
Journal of Chromatography A, 1997
Enantioseparation in capillary electrophoresis using 2-O-(2-hydroxybutyl)-â-CD as a chiral selector The resolving ability of 2-O-(2-hydroxybutyl)-b-CD (HB-b-CD) with different degrees of substitution (DS = 2.9 and 4.0) as a chiral selector in CZE is reported in this work. Fourteen chiral drugs belonging to different classes of compounds of pharmaceutical interest such as b-agonists, antifungal agents, ageneric agents, etc., were resolved. The effects of the DS of HB-b-CD on separations were also investigated. The chiral resolution (R s) was strongly influenced by the concentrations of the CD derivative, the BGE, and the pH of the BGE. Under the conditions of 50 mmol/L Tris-phosphate buffer at pH 2.5 containing 5 mmol/L HB-b-CD, all 14 analytes were separated. The very low concentration necessary to obtain separation was particularly impressive. The DS had a significant effect on the resolution of the chiral drugs and the ionic strength of the separation media; hence, the use of a well-characterized CD derivative is crucial.
Journal of Chromatography A, 2002
A total of 26 different cyclodextrin (CD) derivatives with different functional groups and degrees of substitution were tested against 35 basic pharmaceutical compounds in an effort to investigate their effectiveness as chiral selectors for enantiomeric separation in capillary electrophoresis (CE). Testing was performed under the same conditions using a low pH buffer (25 mM phosphate buffer at pH|2.5). Five CD derivatives, namely, highly sulfated-b-CD, highly sulfated-a-CD, hydroxypropyl-b-CD (degree of substitution|1), heptakis-(2,6-O-dimethyl)-b-CD, and heptakis(2,3,6-O-trimethyl)-b-CD were identified to be most effective for enantiomeric separations and have a wide range of enantiomeric selectivity towards the model compounds. Over 90% of the model compounds were enantiomerically resolved with the five identified CD derivatives, at a minimum resolution of 0.5. An additional 20 compounds were also tested to demonstrate the validity of the identified CD derivatives. The five CD derivatives were recommended as the starting chiral selectors in developing enantiomeric separation methods by CE.
Use of β-cyclodextrin polymer as a chiral selector in capillary electrophoresis
Journal of Chromatography A, 1994
of several basic compounds of pharmaceutical interest were successfully separated by capillary electrophoresis using a modified P-cyclodextrin polymer. As the cyclodextrin contained carboxylic groups, the chiral selector could be used in either an uncharged or a charged mode, selecting the appropriate pH of the background electrolyte. The effect of the pH of the background electrolyte on the effective mobility, resolution and selectivity was studied in the range 2.6-6.2 for the enantiomer resolution of P-hydroxyphenylethylamine, norphenylephrine, terbutaline, ephedrine, norephedrine, ketamine, epinephrine and propranolol. Very good enantiomeric resolution was achieved for all the compounds except for ephedrine and norephedrine (R < 0.5). An increase in the pH of the electrolyte caused an inversion of mobility for either terbutaline and propranolol owing to strong complexation with the negatively charged polymer.
Use of cationic cyclodextrin for enantioseparation by capillary electrophoresis
Journal of Chromatography A, 1998
The usability of 2-hydroxy-3-trimethylammoniopropyl-β-cyclodextrin for chiral discrimination of various basic and acidic substances is described. The dependence of chiral separation on cyclodextrin (CD) concentration and pH value was investigated. Altering the pH value the migration order of the enantiomers of acidic analytes could be changed. Due to the quaternary ammonium structure of the CD molecule, a reversal of the electroosmotic
Journal of Chromatography A, 2005
A facile synthetic approach for mono-6-amino-6-deoxy--cyclodextrin (-CD-NH 2) was proposed. Its hydroxy chloride salt, mono-6ammonium-6-deoxy--cyclodextrin chloride (-CD-NH 3 Cl) was further prepared and used for the enantioseparation of various anionic and ampholytic analytes by capillary electrophoresis (CE). The effect of background electrolyte (BGE) pH and selector concentration on the enantioseparation was studied. Results showed that -CD-NH 3 Cl displayed powerful chiral resolution ability towards anionic analytes. In addition, baseline separation of a standard mixture consisting of eight acids was achieved within 35 min.
Analytica Chimica Acta, 2006
The chiral resolving ability of a novel single-isomer cationic -cyclodextrin (CD), mono-6 A-propylammonium-6 A-deoxy--cyclodextrin chloride (PrAMCD), as a chiral selector in capillary electrophoresis (CE) is reported in this work for the enantioseparation of hydroxy, carboxylic acids and amphoteric analytes. The effect of chiral selector concentration on the resolution was studied. Good resolutions were achieved for hydroxy acids. Optimum resolutions were obtained even at 3.5 mM CD concentration for carboxylic acids. The electrophoretic method showed good linearity and reproducibility in terms of migration times and peak areas, which should make it suitable for routine analysis. In addition, baseline chiral separation of a six-acid mixture was achieved within 20 min. PrAMCD proved to be an effective chiral selector for acidic analytes.
Enantioselective determination by capillary electrophoresis with cyclodextrins as chiral selectors
Journal of Chromatography A, 2000
This review surveys the separation of enantiomers by capillary electrophoresis using cyclodextrins as chiral selector. Cyclodextrins or their derivatives have been widely employed for the direct chiral resolution of a wide number of enantiomers, mainly of pharmaceutical interest, selected examples are reported in the tables. For method optimisation, several parameters influencing the enantioresolution, e.g., cyclodextrin type and concentration, buffer pH and composition, presence of organic solvents or complexing additives in the buffer were considered and discussed. Finally, selected applications to real samples such as pharmaceutical formulations, biological and medical samples are also discussed.
The role of cyclodextrins in chiral capillary electrophoresis
Electrophoresis, 2008
The members of the enantiomeric pairs frequently show rather different biological effects, so their chiral selective synthesis, pharmacological studies and analysis are necessary. CE has unique advantages in chiral analysis. The most frequently used chiral selectors are CDs in this field. This paper gives a short view on the advantages on CE in direct chiral separations, emphasizing the role of CDs. The reason for the broad selectivity spectra of CDs is discussed in detail. The physical background of chiral selective separations is briefly shown in CE. Their interaction mechanisms are shortly defined. The general trend of their use is statistically evaluated. Most frequently used CDs and CD derivatives are characterized. Advantages of ionizable CDs and single-isomer derivatives are shown. The general trend of their use is established.
Phosphated cyclodextrins as new acidic chiral additives for capillary electrophoresis
Journal of Microcolumn Separations, 1997
The study describes the use of ␣ , , and ␥ phosphated cyclodextrins Ž . Ž . CDs for chiral separation by capillary electrophoresis CE . A systematic study was performed to establish the effect of such variables as the type and concentration of chiral selectors as well as the pH and ionic strength of buffer and organic modifiers. It was found that CDs with acidic character offer high chiral selectivity toward basic compounds. These CDs can give chiral recognition features toward molecules in their ionized as well as in their undissociated form. The phosphated cyclodextrins were also found to have adsorptive properties resulting in mixedmigration mechanism, and some guidelines are given to avoid this side effect. A number of racemic drug molecules were used as model compounds to demonstrate optimization procedures of the competing parameters in the analysis.