betadex and phenylcarbamic-acid

This paper reports an effective approach for the fabrication of a novel hybrid bilayer cyclodextrin (CD) chiral stationary phase (CSP), where native and perphenylcarbamoylated-β-CD were successively immobilized onto silica surface via a two-step click approach to form a bilayer CD structure. By decorating the bulky phenylcarbamoylated CD onto the unmodified CD silica, the CSP can provide multiple interaction sites such as H-bonding (-OH, C=O, -NH-), steric effects, π-π, dipole-dipole and inclusion complexation interactions, which help to broaden the CSP's enantioselectivity profile and enhance the enantioselectivity to some specific analytes. A group of enantiomer pairs such as isoxazolines, bendroflumethiazide, indoprofen, diperodon, fenoterol, atropine, styrene oxide and dansyl amino acids can be baseline or partially separated on the current CSP under reversed phase high performance liquid chromatography (RP-HPLC). The selectivity and resolution of 4NPh-OPr reached 5.25 and 13.97, which is an exciting achievement for the enantioseparations by CD CSPs.

Topics: beta-Cyclodextrins; Carbamates; Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Click Chemistry; Silicon Dioxide; Stereoisomerism

Columns packed with vancomycin coupled to an achiral C18 column and beta-cyclodextrin were used for the separation and the determination of enantiomers of alkoxysubstituted esters of phenylcarbamic acid in blood serum. The method involves off-line SPE, the separation of the racemate on a reversed-phase stationary phase, and the separation of the enantiomers on a chiral stationary phase. The limit of detection was 1.0 microg/ml for the vancomycin column and 10.0 microg/ml for the beta-cyclodextrin column in standard solution. In vitro degradation studies of enantiomers demonstrated a difference in the concentation of the enantiomers after the treatment. It was found that the rate constants of R(-)- and S(+)-forms of enantiomers are not significantly different.

Topics: beta-Cyclodextrins; Carbamates; Chromatography, High Pressure Liquid; Chromatography, Ion Exchange; Cyclodextrins; Indicators and Reagents; Kinetics; Stereoisomerism; Teicoplanin; Vancomycin

A direct analytical method of pindolol enantiomers in body fluids was developed by means of column-switching semi-microcolumn liquid chromatography/tandem mass spectrometry (LC-MS/MS). A pre-column packed with a silica-based cation-exchanger was used for on-line sample cleanup. Subsequent enantioseparation was conducted with a phenylcarbamate-beta-cyclodextrin (ph-beta-CD) bonded semi-micro chiral column (2.0 mm inner diameter (i.d.)). A 25-microl aliquot of serum/urine samples was directly injected into the system after simple filtration with a membrane filter. Separated enantiomers were monitored with positive electrospray ionization (ESI) and selected reaction monitoring (SRM). R(+)- and S(-)-pindolol in serum and urine were determined separately within 16 min at a resolution factor of 1.9. The detection limits at a signal-to-noise (S/N) ratio of 5 were 0.13 ng ml(-1) for both enantiomers. The linearity of the method was in the range of 0.25-100 ng ml(-1) with regression coefficient greater than 0.997. Recoveries from spiked serum and urine samples, estimated by the external standard method, were between 94.8 and 117.6% with a relative standard deviation (RSD) ranging from 2.1 to 18%.

Topics: Adrenergic beta-Antagonists; beta-Cyclodextrins; Carbamates; Chromatography, Liquid; Cyclodextrins; Humans; Pindolol; Spectrometry, Mass, Electrospray Ionization; Stereoisomerism