Radiation induced degradation of ciprofloxacin and norfloxacin: Kinetics and product analysis

Ionizing radiation induced degradation of two fluoroquinolone antibiotics, ciprofloxacin and norfloxacin was investigated in 0.1 mmol dm(-3) aqueous solutions. The rate constants, directly determined by pulse radiolysis, were 7.2 x 10(9) mol(-1) dm(3) s(-1) and 5.4 x 10(9) mol(-1) dm(3) s(-1 )for (OH)-O-center dot reaction and 8.2 x 10(9) mol(-1) dm(3) s(-1) and 7.3 x 10(9) mol(-1) dm(3) s(-1) for hydrated electron reaction with ciprofloxacin and norfloxacin, respectively. Absorption bands of several transient intermediates were observed on the pulse radiolysis spectra. For end product characterization samples were irradiated in a Co-60-gamma irradiation chamber, they were analyzed by taking the UV-Vis spectra and by LC separation with MS detection. Based on their structures, most of the products presumably had lost their antibacterial activity. For both compounds products reflecting reaction on the quinolone part (hydroxylated molecules) or on the piperazinyl moiety (desethylene derivatives) were observed.