Eleven quinolone antibacterials have been analyzed by HPLC. The effect
s of different pH values and organic modifiers on chromatographic beha
viour are discussed. Moreover the influence on separation mechanism of
different counter-ions at various concentrations in the eluent has be
en investigated. Two different chromatographic methods have been selec
ted, that allow the simultaneous analysis of quinolones containing or
not a piperazinyl moiety, respectively.