Enantioseparation of amino acids, α‐hydroxy acids, and dipeptides by ligand‐exchange CEC using silica‐based chiral stationary phases

Abstract

This work deals with the application of silica-based ligand-exchange chiral stationary phases (CSPs) for the enantioseparation of underivatized amino acids, alpha-hydroxy acids, and dipeptides with packed CEC. Two different possibilities of preparing silica-based CSPs are presented. One phase contains L-4-hydroxyproline chemically bonded via a spacer to 3 mum silica material. The other approach makes use of N-decyl-L-4-hydroxyproline dynamically coated on a reversed-phase packed capillary. Dynamical coating of reversed-phase material represents a simple alternative to prepare CSP. A comparison of the chemically bonded phase with the dynamically coated CSP by means of resolution of complex-forming analytes is presented. The chemically bonded phase was found to be superior to the dynamically coated phase in terms of resolution of amino acids and dipeptides. However, the dynamically coated CSP was found to be especially suitable for the separation of alpha-hydroxy acids. Both techniques are applicable for enantiomer purity tests.