COMPARATIVE DETERMINATION OF PHOTODEGRADATION KINETICS OF QUINOLONES

The photostabilities of several quinolones have been determined using high performance thin layer chromatography. On irradiation with UVA (350 nm), the photostability decreases in the order: ciprofloxacin (CP) > norfloxacin (NF) > pipemidic acid (PA) > nalidixic acid (NA) > M-193324 > rosoxacin (RS) > oxolinic acid (OA). The photodegradation process in all cases follows first-order kinetics. Furthermore, the quantum yield of fluorescence was determined for each quinolone; these values vary from 0.15 X 10(-2) to 5.15 X 10(-2). The highest PSI(F) value corresponds to CP and NF. These results show that quinolones which possess a piperazine ring at the C-7 position (CP, NF, PA) are less photostable and more fluorescent.