Investigation of an enantioselective non-aqueous capillary electrochromatography system applied to the separation of chiral acids

Tobler, Ernst; Lämmerhofer, Michael; Lindner, Wolfgang

doi:10.1016/s0021-9673(99)01302-3

Cited by 70 publications

(70 citation statements)

References 37 publications

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“…2-Mercaptoethanol was from Merck (Darmstadt, Germany). The synthesis of the silicasupported CSP from Kromasil 100-3.5 mm (Eka Chemicals, Bohus, Sweden) and the O-(tert-butylcarbamoyl) quinine selector as well as the column packing protocol is described in detail elsewhere [12]. A selector coverage of 0.38 mmol/g was calculated from the elemental analysis and the surface area of the Kromasil 100 particles is ca.…”

Section: Methodsmentioning

confidence: 99%

“…If space restrictions do not allow lengthening of the separation channel, enhancement of enantioselectivity by optimization of structural parameters of the chiral monomer appears us to be the most promising solution to the problem. (ii) Monoliths prepared from chiral monomer 1 allow a direct comparison with packed columns possessing also the tert-butylcarbamoylquinine-selector moieties, immobilized on thiolmodified silcia particles (3.5 mm) [12]. (iii) Chiral monomers 1 and 4 are derived from quinine and quinidine, respectively, which possess opposite configurations at C 8 and C 9 (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

et al. 2003

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A new chiral monomer derived from cinchona alkaloid, namely O-9-(tert-butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O-9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 microm in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1-co-HEMA-co-EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4-co-HEMA-co-EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

et al. 2003

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“…L. a ammerhofer and Lindner [526] developed an anion exchange CSP based on tert.-butyl quinine carbamate immobilized on silica. This CSP was applied both for the HPLC and CEC separation of amino acid derivatives and was also found to be applicable to non-aqueous CEC [527].…”

Section: Packed Capillariesmentioning

confidence: 99%

Chiral separation by chromatographic and electromigration techniques. A Review

Gübitz

Schmid

2001

Biopharm & Drug Disp

227

135

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This review gives a survey of different chiral separation principles and their use in high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography (TLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) highlighting new developments and innovative techniques. The mechanisms of the different separation principles are briefly discussed and some selected applications are shown.

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“…The CEC separations utilize predominantly reversed phase and ion-exchange modes, performed almost exclusively in buffered aqueous or aqueous/organic mixed electrolyte systems. Nonaqueous conditions have been used for chiral separations with polar organic mobile phases [43][44][45][46]. Size-based separation mechanisms have not been fully exploited in CEC, excluding capillary gel electrophoresis, which relies on sieving rather than size exclusion [47].…”

Section: Introductionmentioning

confidence: 99%

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

2003

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We report the successful size-based separations of large, neutral polysaccharides using capillary electrochromatography (CEC). As the polysaccharides possessed little chromophore for photometric detection, two separate approaches were taken. In the first approach, indirect detection was combined with size-exclusion chromatography using a sulfonated polystyrene/divinylbenzene stationary phase. The separations were performed using a 300 Å pore size stationary phase under aqueous conditions. Nonsize based interactions were minimal using this material, resulting in an effective calibration range of molecular masses 180 to 112 000 g?mol 21 for pullulans. In the second approach, the polysaccharides were derivatized with phenylisocyanate and were subsequently separated on columns made using a combination of high capacity ionexchanger and a neutral polystyrene/divinylbenzene material of various pore sizes. The sulfonated ion-exchange phase provided the electroosmotic flow, while the mixed pore size material provided the extended calibration range. The linear range for this primarily nonaqueous system using tetrahydrofuran was determined to be from molecular masses 738 to 404 000 g?mol 21 of the original, untagged pullulan. This approach overcame the limited solubility issue associated with analysis of some polysaccharides. Analysis of pullulan and amylose samples by CEC correlated well with results obtained by conventional high-performance liquid chromatography (HPLC). The sizeexclusion electrochromatographic separations provide an alternative mode for determining the relative molecular weights of polysaccharides with reduced sample and solvent consumption, as well as analysis times.

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Investigation of an enantioselective non-aqueous capillary electrochromatography system applied to the separation of chiral acids

Cited by 70 publications

References 37 publications

Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivity

Chiral separation by chromatographic and electromigration techniques. A Review

Size‐exclusion capillary electrochromatographic separation of polysaccharides using polymeric stationary phases

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