Sorption of norfloxacin in soils: Analytical method, kinetics and Freundlich isotherms

•The sorption of norfloxacin (NOR) was studied in four Brazilian soil–water systems.•A strong matrix effect on chromatographic determination of NOR is present.•The matrix effect is eliminated by the addition of EDTA.•KF values indicate that NOR is strongly sorbed on the evaluated soils.•NOR is highly immobile in the evaluated soils.

Fluoroquinolones are potent antibacterial agents that are active against a wide range of pathogenic organisms and are widely used in veterinary medicine. Fluoroquinolones and their metabolites may reach the soil through animal excreta or manure and may contaminate water and soils. The degree of sorption of these antimicrobials to soils varies widely, as does the mobility of these drugs. In the present study, sorption of norfloxacin in four soils of the state of São Paulo was investigated with batch equilibrium experiments. A strong matrix effect on the chromatographic determination of norfloxacin was verified. Sorption kinetics were best fit by a pseudo second-order model (r > 0.99), and sorption/desorption isotherms were well fit by the Freundlich model in log form (r > 0.97). Norfloxacin showed high affinity for soil particles, with KF sorption values ranging from 643 to 2410 μg1−1/n(cm3)1/ng−1 and KF desorption values ranging from 686 to 2468 μg1−1/n(cm3)1/ng−1. The high desorption KF values indicate that norfloxacin is highly immobile in the evaluated soils.

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