Optimization of detection sensitivity for enantiomers of metoprolol on silica-bonded α1-acid glycoprotein

Abstract

On the chiral phases CHIRAL-AGP and EnantioPac, organic modifiers, pH and temperature have been varied with isocratic and gradient techniques to obtain minimum retention and maximum peak height by baseline resolution of R-and S-metoprolol. The decrease in retention obtained by gradient elution gives, by limiting baseline resolution, 20–60% greater peak heights than those obtained by the isocratic technique. A reduction of the retention by a change in the pH is more favourable than addition of modifiers such as acetonitrile or 2-propanol. It gives a smaller decrease in resolution by isocratic elution and a pH gradient can give considerably stronger peak compression than an acetonitrile gradient as indicated by an estimation of the detection limits. For metoprolol enantiomers, CHIRAL-AGP gives about three times lower reduced plate heights than does EnantioPac.