Design of chiral LC separations for calcium antagonists on alpha 1-acid glycoprotein and ovomucoid columns.

Three chiral calcium antagonist drugs, gallopamil and two dihydropyridine derivatives, have been successfully separated within short retention times using both the alpha 1-acid glycoprotein chiral stationary phase (Chiral-AGP) and the ovomucoid column (Ultron ES-OVM). Aqueous buffer at defined pH is modified by the addition of an organic component, in order to modulate the retention properties of each system. Optimization of pH and organic modifier is carried out using the modified simplex method, with Kaiser's peak separation function as a criterion. The influence of pH and percentage of organic modifier on retention, selectivity, resolution and column performance are discussed for the two dihydropyridines analysed on Chiral-AGP and Ultron ES-OVM stationary phases. A new method is proposed as a new chiral system suitability test for these protein-based phases, utilizing a racemic mixture of closely eluting verapamil enantiomers as a probe.