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

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 Sao 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 K-F sorption values ranging from 643 to 2410 mu g(1-1/n)(cm(3))(1/n)g(-1) and K-F desorption values ranging from 686 to 246 mu g(1-1/n)(cm(3))(1/n)g(-1). The high desorption K-F values indicate that norfloxacin is highly immobile in the evaluated soils. (C) 2014 Elsevier Ltd. All rights reserved.