Enantioseparation of dansyl amino acids by HPLC on a monolithic column dynamically coated with a vancomycin derivative.

In this work a chiral stationary phase was prepared by dynamically coating a monolithic reversed-phase HPLC column with a vancomycin-derivative as chiral selector. A hydrophobic alkyl-chain was attached to the vancomycin molecule, providing the immobilization of the chiral selector on the reversed-phase material. Dansyl amino acids were chosen as model analytes for testing the separation power of the dynamically coated phase. All investigated compounds were separated into their enantiomers. Compared with a conventionally packed vancomycin-CSP, a reversal of the enantiomer elution order was obtained.

Enantioseparation of amino acids and alpha-hydroxy acids on ligand-exchange continuous beds by capillary electrochromatography.

A new chiral stationary phase based on continuous bed (CB) technology using L-prolinamide as a chiral selector was prepared. Its ability for enantioseparation of amino acids and alpha-hydroxy acids by ligand-exchange CEC was compared with that of a CB containing L-4-hydroxyproline as chiral selector. Preparation was done by a one-step in situ copolyermerization procedure using methacrylamide as monomer, vinylsulfonic acid as charge providing agent and piperazine diacrylamide as crosslinker. L-Prolinamide showed marked enantioselective properties for the separation of amino acids and alpha-hydroxy acids. Furthermore, we show the possibility of simultaneous enantioseparation of amino acids and alpha-hydroxy acids using the CB with L-4-hydroxyproline as chiral selector.

Enantioseparation of amino acids, alpha-hydroxy acids, and dipeptides by ligand-exchange CEC using silica-based chiral stationary phases.

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.