The 3-amino-derivative of γ-cyclodextrin as chiral selector of Dns-amino acids in electrokinetic chromatography (original) (raw)
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Journal of Chromatography A, 2007
Enantiomeric pairs of 11 dansyl derivatives of ␣-amino acids were used as analytes in electrokinetic chromatography to test the ability as chiral selectors of two pure derivatives of -cyclodextrin: the ethylendiamine derivative in primary position (CDen) and a member of a new class of receptors, the cysteamine-bridged hemispherodextrin THCMH. The selectivity obtained by the presence of the hemispherodextrin, appears particularly promising as shown by the large values of resolution obtained. The importance of a detailed analysis of these data is discussed in terms of suggestions for a rational approach to separation science.
Electrophoresis, 1999
Pre-column derivatization allowed stacking amino acid enantiomers on C 18 reversed-phase micro extraction columns, thus facilitating sample loading in capillary HPLC/tandem mass spectrometry. Two tagging reagents, i.e. 7-fluoro-4-nitrobenzoxadiazole (NBD-F) and 1fluoro-2,4-dinitrobenzene (DNB-F) were evaluated. Both of them reacted readily with amino acids at an elevated temperature, resulting in derivatives that were effectively stacked and suitable for a sensitive MS/MS detection as well. Separation of the tagged enantiomers on a teicoplanin chiral stationary phase (CSP) with mobile phases compatible with MS detection was investigated. NBD-amino acid enantiomers (12 pairs) tested were all base-line resolved. However, the efforts to separate DNB-F tagged amino acid enantiomers on this CSP were not successful. Separation conditions including pH, organic modifiers, and column dimension were studied. All the NBD-amino acids studied could be sensitively detected by MS/MS detection set in the negative ion mode, but only a few including NBD-Asp, BND-Glu, NBD-Ser, and NBD-Thr were detected in the positive ion mode. Thus, the selectivity for enantiomeric determination of excitatory amino acids (e.g. Asp and Glu) was further improved by choosing MS/MS detection in the positive ion mode.
Analytica Chimica Acta, 2005
The enantioseparation of a wide spectrum of anionic analytes was successfully performed by using mono(6-amino-6-deoxy)--cyclodextrin (-CD-NH 2). The effects of buffer pH and selector concentration on migration time and resolution of analytes were studied in detail. Good results were obtained for the chiral separations of hydroxy and carboxylic acids. A clear maximum in selectivity was found for most analytes. The introduced positive charge can greatly improve the chiral recognition ability of -CD-NH 2 towards anionic analytes. The binding constants of eight analytes with -CD-NH 2 were determined and suited well with the mobility difference model (by Wren). Moreover, a standard mixture of five acids was baseline separated within 23 min.
Electrophoresis, 2002
Enantioseparation of chiral aromatic amino acids by capillary electrophoresis in neutral and charged cyclodextrin selector modes Simultaneous enantioseparations of 15 racemic aromatic amino acids and L-mimosine for their chiral discrimination were achieved by neutral selector-modified capillary electrophoresis (CE) and by charged selector-modified CE. Among the diverse cyclodextrins (CDs) examined, hydroxypropyl (HP)-a-CD as the neutral selector and highly sulfated (HS)-g-CD as the charged selector provided best chiral environments of different enantioselectivities. Fairly good enantiomeric resolutions were achieved with the HPa-CD mode except for racemic 6-hydroxy-3,4-dihydroxyphenylalanine, threo-3,4dihydroxyphenylserine and homophenylalanine while high-resolution separations of all the enantiomeric pairs were achieved in the HS-g-CD mode except that L-mimosine was not detected and a partial resolution (0.6) for threo-3,4-dihydroxyphenylserine enantiomers. Relative migration times to that of internal standard under the respective optimum conditions were characteristic of each enantiomer with good precision (% RSD: 0.7-3.8), thereby enabling to cross-check the chemical identification of aromatic amino acids and also their chiralities. The method linearity was found to be adequate (r. 0.99) for the chiral assay of the aromatic amino acids investigated. When applied to extracts of three plant seeds, nonprotein amino acids such as L-mimosine (42 mg/g) from Mimosa pudica Linné, and L-3,4-dihydroxyphenylalanine (268 mg/g) from Vicia faba were positively detected along with L-tryptophan, L-phenylalanine and L-tyrosine.
Journal of Pharmaceutical and Biomedical Analysis, 2014
The resolution power of permethylated 6-monoamino-6-monodeoxy-βCD (PMMABCD) - a single isomer, cationic CD derivative - developed previously for chiral analyses in capillary electrophoresis was further studied here. Dansylated amino acids (Dns-AA) were chosen as amphoteric chiral model compounds. Changes in the resolutions of Dns-AAs by varying pH and selector concentrations were investigated and correlated with their structures and chemical properties (isoelectric point and lipophilicity). Maximal resolutions could be achieved at pH 6 or pH 4. The separations improved with increasing concentration of the selector. Baseline or substantially better resolution for 8 pairs of these Dns-AAs could be achieved. Low CD concentration was enough for the separation of the most apolar Dns-AAs. Chiral discrimination ability of PMMABCD was demonstrated by the separation of an artificial mixture of 8 Dns-AA pairs.
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.
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.
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.
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.
Direct capillary zone electrophoretic methods were developed for the separation of the enantiomers of unnatural -methyl-amino acids such as erythro-and threo--methylphenylalanine, -methyltyrosine, -methyltryptophan and -methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid. Capillary zone electrophoresis was carried out using sulfopropylated-␣-CD (SP2-␣-CD), sulfopropylated--CD (SP2--CD) both with a degree of substitution of 2 moles/mole cyclodextrin, and sulfopropylated--CD (SP4--CD) with a degree of substitution of 4 moles/mole -cyclodextrin. The effects of selector and buffer concentrations, electrolyte pH and applied voltage were studied on the separation efficiency. Varying the electrophoretic conditions with application of 20 kV, hydrodynamic injection, unmodified silica capillary, three different buffers (borate, phosphate and acetate) and modified cyclodextrins as chiral selectors all compounds investigated are nearly baseline resolved. The elution sequence was determined in most cases.