Enantioseparation of selected chiral agrochemicals by using nano-liquid chromatography and capillary electrochromatography with amylose tris(3‑chloro-5-methylphenylcarbamate) covalently immobilized onto silica

Abstract

In this paper enantiomers of selected chiral agrochemicals representing various structural classes were separated by using nano-liquid chromatography (nano-LC) and capillary electrochromatography (CEC) employing a capillary column packed with silica particles containing immobilized amylose tris(3‑chloro-5-methylphenylcarbamate) (i-ADMPC) as a chiral selector (CS). Special attention was paid to peak dispersion in nano-LC and CEC instruments used in order to make comparison between these two techniques more reliable. Enantioseparations were studied utilizing methanol (MeOH) or acetonitrile-water (ACNH₂O), both containing 5 mM of ammonium acetate as the mobile phases (MPs). The tested chiral stationary phase (CSP), containing 20% (w/w) of the neutral CS onto native silica, allowed the generation of sufficiently strong electroosmotic flow (EOF) to observe separation of enantiomers of studied agrochemicals in a reasonable time also in CEC mode. Modestly higher efficiencies and enantioresolutions were obtained in CEC than in nano-LC. Just a moderate preference of CEC over nano-LC in this particular study can be explained with a significant mass transfer resistance through the CSP that is caused due to high content of the CS in CSP.

Keywords: Capillary electrochromatography; Chiral agrochemicals; Enantioseparations; Immobilized-amylose tris(3‑chloro‑5-methylphenylcarbamate); Nano-liquid chromatography.