Polar photodegradation products of quinolones determined by HPLC/MS/MS

The photochemical degradation of quinolones in aqueous solution proceeds in two main steps. The first step is the degradation of the piperazine substitution forming 7-amino compounds which are more stable against photolysis than the corresponding parent compound. Further photochemical degradation down to CO2 formed intermediate polar substances. By liquid/liq- uid partition with chloroform/water, ion exchange chromatography and semipreparative HPLC the polar compounds could be isolated. The structures of the photolytically formed pyridone tri- and dicarboxylic acids were elucidated on the basis of HPLC/MS/MS measurement. Additionally the half-life of the main polar compound, 1-cyclopropyl-pyridone-2,3,5-tricarbo- xylic acid was analysed by HPLC.