FLUOROQUINOLONES AS SENSITIZERS OF LANTHANIDE FLUORESCENCE - APPLICATION TO THE LIQUID-CHROMATOGRAPHIC DETERMINATION OF CIPROFLOXACIN USINGTERBIUM

A time-resolved luminescence detection procedure is proposed for the i n vivo liquid chromatographic determination of the important fluoroqui nolone antibiotic ciprofloxacin. In a first step, the sensitized lumin escence of lanthanides (samarium, terbium or europium) by three main f luoroquinolones, i.e. ciprofloxacin, pefloxacin and ofloxacin, was inv estigated. For this purpose, a preliminary study was made in order to determine the photophysical characteristics of the compounds of intere st. Then, in the presence of lanthanide ions, the possibility of chela tion, suggested by the alpha-keto acid skeleton of the fluoquinolone n ucleus, was verified. Among the three lanthanides studied, Tb3+ was th e most efficiently sensitized. Among the fluoroquinolones tested, cipr ofloxacin was the best sensitizer. In a second step, the formation of a terbium chelate with ciprofloxacin was demonstrated in a classical r eversed-phase eluent [methanol-water (50 + 50) containing trichloroace tic acid (pH 2.5)] using a postcolumn device. In this way, the ciprofl oxacin-terbium chelate was selectivity excited at 320 nm and the terbi um emission detected at 545 nm (D-5(4) --> F-7(5) main terbium transit ion). Postcolumn sensitization was performed using an alkaline methano lic reagent (1 X 10(-3) M Tb3+-2 X 10(-2) M triethylamine-1 x 10(-4) M trioctylphosphine oxide). The chemical compatibility between the elue nt and the postcolumn reagent was studied. The analytical characterist ics were established. With the proposed liquid chromatographic method, the time-resolved luminescence detection mode allowed the detection o f 0.25 pmol injected of ciprofloxacin, which easily meets the sensitiv ity required for the determination of fluoroquinolones in biological s amples.