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991.
A high‐performance liquid chromatographic (HPLC) method for enantioseparation of bupropion was developed using two isothiocyanate‐based chiral derivatizing reagents, (S)‐1‐(1‐naphthyl) ethyl isothiocyanate, (S)‐NEIT, and (R)‐α‐methyl benzyl isothiocyanate, (R)‐MBIT. The diastereomers synthesized with (S)‐NEIT were enantioseparated by reversed‐phase HPLC using gradient elution with mobile phase containing water and acetonitrile, whereas diastereomers synthesized with (R)‐MBIT were enantioseparated using triethyl amine phosphate buffer and methanol. Derivatization conditions were optimized and the method was validated for accuracy, precision and limit of detection. The limit of detection was found to be 0.040–0.043 µg/mL for each of the diastereomers prepared with (S)‐NEIT. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
992.
993.
Xiaoyu Zhang Michele E. Lake Adam S. Butterbaugh Kirk A. VanDer Kamp 《液相色谱法及相关技术杂志》2017,40(20):1015-1019
This study demonstrates the first use of a reversed-phase (RP) high-performance liquid chromatography method with a high-pH buffer for the analysis of sodium stearyl fumarate (SSF) from a tablet formulation. After examining the retention time and peak shape using various buffer concentrations, buffer pH, and RP stationary phases, an optimized method was established using the XBridge® BEH C18 at high pH. This column was further evaluated for method specificity, accuracy, precision, linearity, stability, and sensitivity. Finally, the method was successfully used as a convenient and robust analytical procedure to accurately quantitate SSF in stratified tablets from a continuous manufacturing process to confirm the excipient uniformity throughout the process. 相似文献
994.
995.
Chiral analytical method development and application to pre‐clinical pharmacokinetics of pinocembrin
Casey L. Sayre Jody K. Takemoto Stephanie E. Martinez Neal M. Davies 《Biomedical chromatography : BMC》2013,27(6):681-684
An analytical method enabling the detection and quantification of the individual enantiomers of racemic (±) pinocembrin is required to fully characterize its pharmacokinetic disposition. Direct resolution of the enantiomers of pinocembrin was achieved using a novel and simple reversed‐phase high‐performance liquid chromatography method with electrospray ionization and detection by mass spectrometry in rat serum. A Chiralcel® AD‐RH column was employed to perform baseline separation with electrospray positive‐mode ionization with selected ion monitoring detection. The standard curves were linear from 0.5 to 100 µg/mL for each enantiomer. The limit of quantification was 0.5 µg/mL. The assay was applied successfully to stereoselective serum disposition of pinocembrin enantiomers in rats. Pinocembrin enantiomers were detected in serum. Both enantiomers had a serum half‐life of ~15 min in rats. Similar values of volume of distribution between the enantiomers were also observed: 1.76 L/kg for S‐pinocembrin and 1.79 L/kg for R‐pinocembrin. Total clearance was 5.527 L//h/kg for S‐pinocembrin and 5.535 L/h/kg for R‐pinocembrin, and the area under the curve was 1.821 µg h/mL for S‐pinocembrin and 1.876 µg h/mL for R‐pinocembrin. The large volume of distribution coupled with the short serum half‐life suggests extensive distribution of pinocembrin into the tissues. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
996.
Koichiro Shirota Ichirou Yamaguchi Kiyoshi Kanie Tomiki Ikeda Tamejiro Hiyama Ichiro Kobayashi 《Liquid crystals》2013,40(5):555-558
The optical properties of two kinds of photochromic antiferroelectric liquid crystal (AFLC) containing an azo group have been examined. Depending on the substituting group at the chiral centre, these AFLCs showed different photoinduced phase transitions by Ar+ laser light irradiation. This phase transition has led to a new form of optical switching controlled by a bias voltage. In addition, it was found that these AFLCs caused an azimuthal photoalignment effect regulated by linearly polarized Ar+ laser light irradiation. These phenomena were applied to image storage. 相似文献
997.
998.
ABSTRACTWe have studied the properties of biaxial particles interacting via an anisotropic pair potential, involving second-rank quadrupolar and third-rank octupolar coupling terms, using Monte Carlo simulation. The particles occupy the sites of a 2D square lattice and the interactions are restricted to nearest neighbours. The system exhibits spontaneous chiral symmetry breaking from an isotropic phase to a chiral modulated nematic phase, composed of ambidextrous chiral domains. When twofold axes of quadrupolar and octupolar tensors coincide this modulated phase appears to be the ambidextrous cholesteric phase with pitch comparable to a few lattice spacings. The associated phase transition is first order. 相似文献
999.
Maja Trček George Cordoyiannis Brigita Rožič Vassilios Tzitzios George Nounesis Samo Kralj 《Liquid crystals》2017,44(10):1575-1581
We report on the stabilisation of the liquid-crystalline, twist-grain boundary A (TGBA) phase in mixtures of a chiral liquid crystal and surface-functionalised spherical Au nanoparticles (NPs) of 10 nm diameter. The results, obtained by calorimetric, optical, small-angle X-ray and plasmon resonance measurements, demonstrate that a TGBA phase, which is metastable for the pure liquid crystal host, can be effectively stabilised for a 3 K range in the presence of NPs. Moreover, the role of NPs size on the TGBA stabilisation is briefly discussed. 相似文献
1000.
ABSTRACTA homologous series of new chiral liquid crystal compounds, MnBEB (n = 4–10), was prepared by covalently linking a chiral (–)-menthyl with biphenyl-benzoate via a dicarboxylic spacer of varying length and parity. A combination of analysis methods, such as FT-IR, 1H NMR spectra, differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction was carried out to systematically investigate their phase structures and phase transition behaviours. The length and parity of the flexible spacers has a profound influence on the Tm and Tc and a modest odd-even effect is observed for the chiral liquid crystal compounds MnBEB. Only compound M4BEB developed an N* phase with selectively reflection on heating and a blue phase on cooling process. In addition, increasing the length of the flexible spacers tends to narrow the temperature range of the N* phase and widen the smectic phase, moreover, the pitch becomes longer with the spacer increases. 相似文献