Separation of structural isomers using cyclodextrin-polymers coated on silica beads

Summary Several -cyclodextrin (CD)-bonded stationary phases for high performance liquid chromatography (HPLC) were prepared, based on silica beads coated with a poly(alkylamine), [poly(ethyleneimine)(PEI)]. In order to obtain stationary phases with a high content of CD and maximum accessibility of the CD cavity, the functionalization was carried out after the coating, using the mono-tosyl derivative of CD as the intermediate. The ability of these supports to separate ortho, meta and para isomers of some disubstituted benzene derivatives was examined. The contribution of the amino groups of the polymer and of the CD cavity to the separation process is discussed. The resolution is mainly based on the difference in the stability of the complexes of the various isomers with CD. The influence of the amount of CD on the height of the theoretical plate is also studied.     

Spectroscopic study of the complexes of poly(N-methacryloyl-L-asparagine) with palladium (II)

The complexes formed between palladium (II) and a polymeric ligand derived from L -asparagine, poly(N-methacryloyl-L -asparagine) (PNMAsn) have been investigated by electronic absorption and circular dichroism. N-isobutyroyl-L -asparagine (NIBAsn) was also synthesized and studied with the purpose of comparison with its polymeric analog. NIBAsn gives two complexes: at low pH, an optically active complex between one carboxylate and one secondary amide nitrogen (so-called 1N complex), and at higher pH, a 2N complex involving the primary and secondary amide group. This complex is also optically active. PNMAsn gives at low pH a 1N complex similar to that of NIBAsn, but at higher pH the 2N complex is formed between two carboxylate groups and two secondary amide groups of two different side chains of the polymer. At very high pH this 2N complex is hydrolyzed, i.e., the carboxylate-palladium bonds are replaced by hydroxyle-palladium bonds, and the complex becomes optically inactive.     

Spectroscopic study of the interaction of poly(ε-N-methacryloyl-L-lysine) with copper(II)

The complexes formed between copper(II) and a polymeric ligand derived from L -lysine, poly(ε-N-methacryloyl-L -lysine) have been investigated by electronic absorption, circular dichroïsm, and EPR spectroscopy. The model molecule, ε-N-isobutyroyl-L -lysine was also studied with the purpose to distinguish between the effects due to the polymeric nature of the ligand and its intrinsic complexing properties. All experiment results are consistent with the existence of two CuL and CuL₂ complexes for both model and polymer Cu systems with no deprotonation of the amide group. The two complexes involve only the carboxyl and amino groups. With the polymer, the CuL₂ complex is the main species, even at low pH and low [ligand]/[metal] ratio. This is attributed to the high local concentration of ligand in the vicinity of the polymer chain. With the model molecule, on the contrary, the distribution of the two complexes is strongly dependent on the pH and the [ligand]/[metal] ratio.     

High performance liquid chromatography of structural isomers using a cyclodextrin-poly(allylamine) coated silica column

Summary High performance liquid chromatography (HPLC) separation of substituted phenols by isocratic elution was investigated using a β-cyclodextrin-bonded column. The HPLC support was prepared in-house. This support was based on silica beads coated with a β-cyclodextrin-containing poly(allylamine). The retention behavior of some substituted phenol isomers and aromatic compounds was studied. The contribution of the amino groups of the polyamine and of the β-cyclodextrin cavity to the separation process is discussed. Two retention mechanisms, inclusion complex formation and acidbase interaction, were found. The effect of the composition and pH of the mobile phase on the separation was also examined.     

High performance liquid chromatography of structural isomers using a cyclodextrin-poly(allylamine) coated silica column

Summary High performance liquid chromatography (HPLC) separation of substituted phenols by isocratic elution was investigated using a β-cyclodextrin-bonded column. The HPLC support was prepared in-house. This support was based on silica beads coated with a β-cyclodextrin-containing poly(allylamine). The retention behavior of some substituted phenol isomers and aromatic compounds was studied. The contribution of the amino groups of the polyamine and of the β-cyclodextrin cavity to the separation process is discussed. Two retention mechanisms, inclusion complex formation and acidbase interaction, were found. The effect of the composition and pH of the mobile phase on the separation was also examined.     

THE THYMIDINE-PSORALEN PHOTOADDITION. A MODEL APPROACH

Abstract— In order to investigate the photoreactions between the thymidine and the psoralen chromophores and to devise a synthetic route to prepare thymidine-5-methoxypsoralen adducts, we have prepared and studied a compound in which thymidine is linked to a 5-methoxypsoralen derivative by a diester chain. Irradiation at 365 nm carried out at usual concentrations (10–³ M ) leads exclusively to one diastereoisomer of an intramolecular 3,4 cis-anti [2+2] adduct. No photodimerization is observed in these conditions. These results are compared to those obtained for models studied previously in which the thymine and the psoralen rings are linked by polymethylenic chains of varying length.     

High-performance liquid chromatographic stationary phases based on silica coated by in situ polymerization of a methacryloyl beta-cyclodextrin monomer: synthesis, characterization, and chromatographic evaluation

Porous silica beads have been coated with a 2-hydroxy-3-methacryloyloxypropyl beta-cyclodextrin polymer by in situ free-radical polymerization in water. This system has been developed for use as a stationary phase in high-performance liquid chromatography. In the conditions used, the coating efficiency is controlled by the initial concentration of the monomer. The polymer coating has been quantitated by thermogravimetric analysis. The stationary phases have also been characterized by means of the nitrogen adsorption/desorption method, energy dispersion X-ray analysis, and scanning electron microscopy to investigate the changes in the porosity, as well as in the surface properties generated by the coating process. Finally, the chromatographic evaluation has been made under normal- and reversed-phase elution conditions.