In this work, analytical methods based on solid surface room-temperature phosphorimetry were developed aiming the selective determination of fluorquinolones. More spectilly, thorium nitrate was evaluated as phosphorescence inducer aiming the sequential determination of norfloxacin (NOR) and levofloxacin (LEV), selective determination of NOR in presence of ciprofloxacin (CIP), as well as the selective determination of CIP in the presence gatifloxacin (GAT) or moxifloxacin (MOX). In order to that, the phosphorescence induced by thorium nitrate was compared with the ones achieved using other traditionally employed heavy atom enhancers in solid surface room-temperature phosphorimetry (SSRTP). Univariated studies were made in order to evaluate the effect of the amounts of heavy atom salt and surface modifier present in the substrate as well as the influence of the pH of the analyte carrier solution. The interaction among these factors were also studied through experimental factorial desings (23). After the definition of the analytical strategy to be employed, analytical methods were developed for the determination of NOR, LEV and CIP in simulated mistures and analyte spiked urine without employing any procedure to physically separate the analyte from the others components of the sample. In order to do that, the use of syncronized scanning was fundamental. The analytical figures of merit achieved using thorium nitrate and cadmium acetate (heave atom inducer already reported in the literature for fluorquinolones) were campared. In both cases, linear analytical responses in function of the amount of analyted present in the substrate were achieved (R2>0,99). Good repetitivity of results and sensibility (evaluated through the estimation of the limits of detection and quantification) were in the ng order. When testing pharmaceutical formulations and spiked urine, the use of Th(NO3)4 showed clear advantage over Cd(OAc)2, allowing the sequential determination of NOR/LEV and the selective determination of NOR in the presence of CIP. The selective determination of NOR using Th(NO3)4 could be made for mixtures containing up to five times more LEV or CIP in molar proportion. For the developed method aiming the determination of CIP in mistures containing GAT, Th(NO3)4 was found to be more adequate heavy atom enhancer than Cd(OAc)2. The method was free from interferences for samples containing two times more GAT than CIP (in molar proportion). However, interferences observed for mixtures containing higher amounts of GAT could be easily corrected by the using of the standard addition method for quantification. In mixtures containing CIP and MOX, the developed method using Th(NO3)4 was suitable for mixtures containing equimolar proportions of these two fluorquinolones. Spectral interferences were observed for higher amounts of MOX. Such interference could not be resolved due to close (lambda) values characteristic for the two FQs. However, for the method using Cd(OAc)2 in mixtures containing CIP/MOX in molar proportion more them 1:2 only non spectral interferences were observed, but this interferences can be corrected by the use of proper calibration strategy. This was the only situation where Cd(OAc)2 demonstrate better results than Th(NO3)4.