New chemiluminescent method of levofloxacin and ofloxacin determination based on terbium (III)-sensitized fluoroquinolone-KBrO3 reaction

Fluoroquinolones can be oxidized with some agents, in this study selected fluoroquinolones (levofloxacin, ofloxacin, ciprofloxacin, norfloxacin, pefloxacin and enrofloxacin) were oxidized with potassium bromate in the presence of terbium (III) ions. According to the kinetic and spectral analysis of chemiluminescence emitted by the above systems, the terbium (III) ions were the only emitter. The excitation of the lanthanide ion was a result of the process of energy transfer from the products of fluoroquinolones oxidation to Tb(III) ions. The highest intensity of chemiluminescence was obtained for levofloxacin and ofloxacin containing an alkoxy substituent at C-8 in the quinoline ring. The chemiluminescence intensity was correlated linearly (r = 0.9994) with the concentration of ofloxacin (or levofloxacin) in the range 1 x 10(-6) to 4 x 10(-5) mol L-1; the detection limit was 3 x 10(-7) mol L-1 for both fluoroquinolones. In the optimized conditions, the chemiluminescence of the levofloxacin (or ofloxacin)-Tb(III)-KBrO3-H2SO4 systems was used to determine these compounds in a mixture of fluoroquinolones and in pharmaceuticals.