Enantioselective cholesteric liquid crystalline membranes characterized using nonchiral HPLC with circular dichroism detection

Han, Sangil; Martin, Stephen M.

doi:10.1016/j.memsci.2010.09.039

Cited by 11 publications

(7 citation statements)

References 29 publications

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“…In addition, the higher temperatures in the isotropic phase serve to weaken intermolecular interactions, such as hydrogen bonding and van der Waals interactions, between the solutes and the LC phase. This agrees with prior results from our laboratory showing that 5CB/COC membranes exhibited lower selectivity of 1.07 in the isotropic phase than 1.2 in the cholesteric phase …”

Section: Resultssupporting

confidence: 93%

“…Analysis of the enantiomer solutions was carried out using an HPLC system (Shimadzu, Kyoto, Japan) consisting of an LC‐20AB binary pump unit, a CBM‐20A communication unit, and circular dichroism (CD) detector (CD‐2095, Jasco Easton, MD, USA). The CD detector allows the determination of enantiomer compositions by measuring the CD and UV signals simultaneously without the use of a specific chiral HPLC column …”

Section: Methodsmentioning

confidence: 99%

“…The spectra and chromatograms were collected and analyzed using Spectra Manager software (Jasco). The compositions of the left‐handed and right‐handed enantiomers were obtained using the g‐factor (the ratio of the CD to UV signals), and the enantiomer concentrations were obtained from UV intensity . Figure shows the linear dependence of the anisotropy factor (g) on the enantiomeric excess (ee) of phenylglycine solutions with the various total solute concentrations (see the previous study for the linear dependence of g‐factor on 1‐phenylethanol solutions).…”

Section: Methodsmentioning

confidence: 99%

“…The CD detector allows the determination of enantiomer compositions by measuring the CD and UV signals simultaneously without the use of a specific chiral HPLC column. 19,20 Aqueous 1-phenlyethanol samples, 20 mL, were injected into the HPLC-CD detection system with a methanol/water (50:50) mobile phase, and the CD and UV signals were monitored at a wavelength of 260 nm. Aqueous phenylglycine samples, 20 mL, were injected into the HPLC-CD detection system with a methanol/water (5:95) mobile phase, and the CD and UV signals were monitored at a wavelength of 228 nm.…”

Section: Enantiomer Detectionmentioning

confidence: 99%

“…This agrees with prior results from our laboratory showing that 5CB/COC membranes exhibited lower selectivity of 1.07 in the isotropic phase than 1.2 in the cholesteric phase. 19 Supported ChLC membranes produced using 5CB with no added chiral dopant exhibited no enantioselectivity ( Table 2). This is due to the absence of either phase or molecular chirality.…”

Section: The Effect Of Lc Phase and Hydrogen Bonding On 1-phenylethanmentioning

confidence: 99%

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Enantioselective separations using chiral supported liquid crystalline membranes

et al. 2012

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Porous and nonporous supported liquid crystalline membranes were produced by impregnating porous cellulose nitrate supports with cholesteric liquid crystal (LC) materials consisting of 4-cyano-4'-pentylbiphenyl (5CB) mixed with a cholesterol-based dopant (cholesteryl oleyl carbonate [COC], cholesteryl nonanoate [CN], or cholesteryl chloride [CC]). The membranes exhibit selectivity for R-phenylglycine and R-1-phenylethanol because of increased interactions between the S enantiomers and the left-handed cholesteric phase. The selectivity of both phenylglycine and 1-phenylethanol in 5CB/CN membranes decreases with effective pore diameter while the permeabilities increase, as expected. Phenylglycine, which is insoluble in the LC phase, exhibits no transport in the nonporous (completely filled) membranes; however, 1-phenylethanol, which is soluble in the LC phase, exhibits transport but negligible enantioselectivity. The enantioselectivity for 1-phenylethanol was higher (1.20 in 5CB/COC and 5CB/CN membranes) and the permeability was lower in the cholesteric phase than in the isotropic phase. Enantioselectivity was also higher in the 5CB/COC cholesteric phase than in the nematic phase of undoped 5CB (1.03). Enantioselectivity in the cholesteric phase of 5CB doped with CC (1.1), a dopant lacking hydrogen bonding groups, was lower than in the 5CB/COC phases. Finally, enantioselectivity increases with the dopant concentration up to a plateau value at approximately 17 mol%.

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Section: Resultssupporting

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Enantiomer Detectionmentioning

confidence: 99%

Section: The Effect Of Lc Phase and Hydrogen Bonding On 1-phenylethanmentioning

confidence: 99%

See 3 more Smart Citations