Analysis of polymer additives in high-temperature liquid chromatography.

A high-temperature liquid chromatographic technique is employed for the separation of commercially available polymer additives to enhance the resolution and speed. Separation efficiencies and elution behaviors for seven phthalate plasticizers and five antioxidants are evaluated at elevated column temperatures and with a thermal gradient. Diamondbond C18 (octadecylsilica), Zirchrom PS (zirconia-based polystyrene), and Zirchrom PBD (zirconia-based polybutadiene) columns are selected for the study because of their thermal stability.

Liquid chromatographic determination of novel aminithiazolecarboxamide fungicide residues in soil and crops using online solid-phase extraction.

A simple and convenient liquid chromatographic method has been developed and applied to the analysis of the novel aminothiazolecarboxamide fungicide, ethaboxam, in soil and crops. After the isolation and concentration of analyte from soil and crops, clean-up and separation of sample solutions are performed by high-performance liquid chromatography with online solid-phase extraction. Good linearity (r2 > 0.

Studies of poly(styrene-co-allyl alcohol)/polyester blends using Fourier transform infrared spectroscopy and imaging.

The interaction of poly(styrene-co-allyl alcohol) and aliphatic polyester was studied using FT-IR spectroscopy. The hydrogen bonding between two polymers was investigated by monitoring C=O and OH stretching modes with the variation of concentration and temperature. The phase-separated morphology was also observed using FT-IR imaging, where the spectroscopic analysis of each phase is available.

Reversed-phase liquid chromatographic method for the analysis of aminoglycoside antibiotics using pre-column derivatization with phenylisocyanate.

A pre-column derivatization liquid chromatographic method has been developed for the analysis of aminoglycoside antibiotics using phenylisocyanate as a derivatization reagent. Derivatives including kanamycin, neomycin and gentamicin were formed by reaction of the analytes with phenylisocyanate in the presence of triethylamine. Phenylisocyanato groups were attached to corresponding amino groups of aminoglycoside and their molecular mass was confirmed by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS).

Determination of melagatran in rabbit plasma by high-performance liquid chromatography with automated column switching.

Melagatran is an active thrombin inhibitor showing oral and parenteral bioavailability for antithrombotic therapy. A simple and convenient liquid chromatographic method has been developed and applied to the analysis of melagatran in rabbit plasma. The clean-up and separation of the sample solutions were performed by automated on-line column switching HPLC.

New catalyst design for polymerization of norbornene esters by reducing intramolecular interaction.

We have used density functional theory to study palladium-based catalysts commonly used for the polymerization of norbornene derivatives with an ester group. Exo-exo, exo-endo, and endo-endo isomers of catalyst complexes were investigated; the endo-endo isomer was the most stable and inactive due to an intramolecular interaction between Pd and O of the carbonyl group. Phosphine groups are effective in minimizing the Pd-O interaction in the endo-endo isomer and P(C6H11)3 was found to be the most efficient reagent.

Enantiomeric discrimination of pyrethroic acid esters on polysaccharide derived chiral stationary phases.

Enantiomeric separation of pyrethroic acid methyl and ethyl esters was examined on cellulose-based chiral stationary phases (CSPs): chiralcel OD (cellulose tris(3,5-dimethylphenyl carbamate)) and chiralcel OF (cellulose tris(4-chlorophenyl carbamate)). The good resolution of pyrethroic acid esters was achieved on chiralcel OD and OF. Separation factors ranged from 1.

Comparison of reversed-phase liquid chromatographic methods for the separation of new quinolones.

Reversed-phase high-performance liquid chromatography is widely used in the analysis of drug substances and their metabolites. The interaction of quinolones with residual silanol in a silica-based C18 stationary phase causes peak broadening and bad peak shapes and makes it hard to resolve the peak separations. This unusual interaction is studied and finally can be removed by masking the residual silanol of a silica-based C18 stationary phase, then good peak separation is achieved.