Method for determination of fluoroquinolones based on the plasmonic interaction between their fluorescent terbium complexes and silver nanoparticles

We report on a fluorometric method for the determination of the fluoroquinolones levofloxacin (LEV) and moxifloxacin (MOXI). It is based on the Tb(III)-sensitized luminescence that is plasmonically enhanced by silver nanoparticles (Ag NPs). The emission of the Tb(III) complexes has maximum at 545 nm after excitation at 284 nm and is strongly enhanced in the presence of the colloidal Ag NPs. Under optimum experimental conditions, luminescence intensity increases linearly with the concentration in the range from 4.16 x 10(-17)-3.59 x 10(-15) M of LEV, and from 4.98 x 10(-17)-2.49 x 10(-15) M for MOXI with correlation coefficients of 0.9996 and 0.9996, respectively. The limits of detection are 7.19 x 10(-18) M and 8.47 x 10(-18) M, respectively, and the relative standard deviations are 1.3 and 1.5% for 5 replicate measurements at 6.08 x 10(-14) M of LEV and 5.48 x 10(-14) M of MOXI. The method was successfully applied to the determination of LEV and MOXI in pharmaceutical samples, in urine and in serum.