Simultaneous separation of the stereoisomers of 1-amino-2-hydroxy and 2-amino-1-hydroxypropane phosphonic acids by stereoselective capillary electrophoresis employing a quinine carbamate type chiral selector.

Abstract

A stereoselective nonaqueous capillary electrophoresis (CE) method utilizing O-(tert-butylcarbamoyl) quinine as chiral ion-pair agent and additive to the non aqueous background electrolyte was evaluated for the simultaneous separation of the enantiomers and diastereomers of 1 -amino-2-hydroxypropane phosphonic acid besides the corresponding beta-aminophosphonic acid analogs, the stereoisomers of 2-amino-1-hydroxypropane phosphonic acid, in a single run. The separations have been carried out using the partial filling technique to avoid strong background signal from the quinine selector. It conveniently allowed the baseline separation of all eight components of interest (alpha- as well as beta-aminophosphonic acids) as N-2,4-dinitrophenyl derivatives in a single run. Moreover, the absolute configurations of all eight peaks were identified. Compared to the quinine carbamate selector, the corresponding 'pseudo-enantiomeric' O-(tert-butylcarbamoyl) quinidine selector exhibited reserved elution order and nearly identical resolutions. The proposed CE method turned out to be advantageous over stereoselective high-performance liquid chromatography (HPLC) with a quinine carbamate type stationary phase, which showed high enantioselectivity, but failed to simultaneously separate all eight components.