Allylamine-beta-cyclodextrin copolymer. A novel chiral selector for capillary electrophoresis

A novel, positively charged, copolymer of allylamine and 2-hydroxy-3-methacryloyl-beta-cyclodextrin was synthesized to be used as a chiral selector in capillary electrophoresis. In the copolymer, cyclodextrin molecules are spaced from the backbone though a spacer arm which prevents sterical hindrance of the CD cavity. The self-mobility of the CD polymer in its charged form, opposite to the analytes, is the cause for the enhanced separation factor provided by this selector. Moreover, the positive charged polymer induces a reversal of electroosmotic flow which is beneficial in enantioseparations of acidic compounds as it reduces analysis time and increases peak efficiency. The ability of this copolymer to act as a CE chiral selector in the separation of 2,4-dinitrophenylamino acid enantiomers was investigated in coated and uncoated capillaries and its performance was much better then that of native beta-cyclodextrin.

Vinylpyrrolidine-beta-cyclodextrin copolymer: a novel chiral selector for capillary electrophoresis

The synthesis and characterization of a novel polymer consisting of an alkyl backbone and pendant beta-cyclodextrin units, obtained by radical copolymerization of vinylpyrrolidone and methacryloyl-beta-cyclodextrin (PVP-beta-CD), was reported. The ability of this copolymer to act as a capillary electrophoresis (CE) chiral selector was investigated in the separation of a mixture of basic drugs. The influence of polymeric cyclodextrin concentration, temperature, and pH on the separation of the test analytes was assessed and the advantage of using the polymeric selector over native beta-cyclodextrin was demonstrated.

Molecular Conformation and Mobility of Polyamines Adsorbed on Silica Studied by Spin Labeling

Poly(ethyleneimine) and poly(4-vinylpyridine) chains adsorbed on Nucleosil silica have been randomly labeled with nitroxide free radicals. The EPR signal is very sensitive to the molecular Brownian motion of the segments and shows generally at least two different environments: trains adsorbed on the surface with a restricted mobility, and loops and tails protruding into the solution with a fast motion. The rotational correlation times and the relative fraction of each population are given as functions of the coverage achieved and of the specific surface area of the silica for the samples in contact with methanol and sometimes water. The overall picture is consistent with a diffuse layer for the PEI and a more compact one with some heterogeneities for the P4VP. Copyright 1999 Academic Press.

Solid state NMR spectroscopy study of molecular motion in cyclomaltoheptaose (beta-cyclodextrin) crosslinked with epichlorohydrin

Dry and hydrated insoluble cyclomaltoheptaose (beta-cyclodextrin, beta-CD) polymers have been investigated by solid state 13C NMR spectroscopy techniques such as cross polarization/magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning both with (DD-MAS) and without (MAS) dipolar decoupling and CP/MAS dipolar dephasing (dd-CP/MAS) to allow the assignment of the main 13C signals. In the solid state, the presence of water in the samples resulted in a better resolution reflecting increased mobility. Two distinct components (crosslinked beta-CD and polymerized epichlorohydrin) have been found. The molecular mobility of these two components has been analyzed in terms of relaxation parameters such as 13C spin lattice relaxation (T1) and 1H spin lattice relaxation in the rotating frame (T1 rho). The T1 values of the polymers show that the beta-CD trapped inside the polymers does not seem to undergo changes in its mobility whatever the amount of epichlorohydrin. The addition of water to beta-CD significantly increases the T1 values reflecting strong interaction between beta-CD and the solvent. The T1P values obtained reflect the homogeneous nature of the materials.