RESUMO
The 3,5-dimethylphenylcarbamate derivatives of cellulose bearing 3-(triethoxysilyl)propyl residues were immobilized in a capillary format onto a monolithic silica support by intermolecular polycondensation of the triethoxysilyl groups. The resulting columns were used for chiral separations using capillary electrochromatography. The effects of the synthesizing solvent, the selector coating procedure, the chiral selector concentration onto the silica monolith and the mobile phase pH value, on the separation of enantiomers were studied. The column-to-column reproducibility and stability also were evaluated. A test set of 14 chiral substances, including acidic, neutral, bifunctional and basic compounds, was used to investigate the effects of the factors mentioned above. Twelve pairs of enantiomers showed enantioselectivity at some of the different conditions tested. The column-to-column repeatability was satisfactory, and the prepared columns were stable under the adopted analysis conditions.
Assuntos
Eletrocromatografia Capilar/instrumentação , Celulose/análogos & derivados , Fenilcarbamatos/química , Dióxido de Silício/química , Acetamidas/química , Acetonitrilas/química , Eletrocromatografia Capilar/métodos , Celulose/química , Concentração de Íons de Hidrogênio , Cloreto de Lítio/química , Preparações Farmacêuticas/química , Preparações Farmacêuticas/isolamento & purificação , Reprodutibilidade dos Testes , EstereoisomerismoRESUMO
The enantioselective degradation of benalaxyl has been investigated to elucidate its behavior in several agricultural soils and plants (cucumber). Racemic benalaxyl was fortified into five types of agricultural soils and sprayed leaves of cucumber plants, respectively. The degradation kinetics and the enantiomer fraction (EF) were determined by normal-phase high-performance liquid chromatography (HPLC) with diode array detection (DAD) on the chiral column filled cellulose-tri-(3,5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP). The process of the degradation of benalaxyl enantiomers followed pseudo-first-order kinetics in cucumber plant. However, the dissipation phases of benalaxyl enantiomers in soils were biphasic ("slow-fast-slow" process). It has been shown that the degradation of benalaxyl was stereoselective. The results indicated that the (+)-S-benalaxyl showed a faster degradation in plants, while the (-)-R-benalaxyl showed a faster degradation in Soils 3, 4, and 5. No stereoselective degradation was observed in other soils.