Enantiomeric separation of some chiral analytes using amylose 3,5-dimethylphenylcarbamate covalently immobilized on silica by nano-liquid chromatography and capillary electrochromatography.

A new experimental chiral stationary phase containing amylose 3,5-dimethylphenylcarbamate immobilized onto silica gel (i-ADMPC) was packed in 100μm I.D. fused silica capillary and used for the chiral separation of eight selected flavanone derivatives in polar organic mobile phase by using different miniaturized techniques, such as nano-liquid chromatography (nano-LC), capillary electrochromatography (CEC) and pressure-assisted CEC (pCEC). A comparative study of different elution modes in terms of chromatographic efficiency, analysis time and enantiomeric resolution was carried out. In pCEC mode, the highest chromatography performance was obtained applying +2.5kV voltage and inlet pressure 10bar. Under these conditions, the analysis times were shorter than 20min, and chromatographic efficiencies were in the range 33,000-49,000 plates/m (first eluted peak). The solvent versatility of packed i- ADMPC capillary column was also investigated. In nano-LC, the CSP was stressed under the use of strong organic solvents such as ethyl acetate, acetone and methyl t-butyl ether (MTBE). After at least 40 working hours and over 50 sample injections, the CSP resulted to be very stable allowing to achieve good repeatability employing again the mobile phase containing polar organic solvent. Enantioresolutions and chromatographic efficiencies decreased by 1.60 and 10%, respectively as the result of using above mentioned strong solvents.