Trace-Level Determination of Oxolinic Acid and Flumequine in Soil, River Bed Sediment, and River Water Using Microwave-Assisted Extraction and High-Performance Liquid Chromatography with Fluorimetric Detection

This work presents the optimization of analytical procedures for the determination of two antibiotics, oxolinic acid (OA) and flumequine (FL), in bed sediment, river water, and soil samples. Three extraction methods (microwave-assisted extraction (MAE), ultrasonication, and reflux) were tested, and the highest recoveries were obtained with MAE (94 +/- 3% and 95 +/- 3% for OA and FL, respectively). A solid-phase extraction (SPE) clean-up step was optimized by comparing two polymeric sorbents: Oasis HLB and Oasis MAX. The final extracts were analyzed by liquid chromatography with fluorimetric detection. Limits of detection (LOD) obtained for OA and FL in soil and sediment ranged from 0.3 to 0.5 mu g kg(-1). Meanwhile, a novel SPE procedure was also implemented for OA and FL determination in river water samples. It also relied on the use of Oasis MAX, and recovery rates were in the range 90-94%; LODs were 2ng L-1 for both OA and FL. These methods were applied for the analysis of samples taken in the Seine River basin (France). The obtained results demonstrated the widespread occurrence of OA and FL, at ng L-1 and mu g kg(-1) levels in water and sediment/soil, respectively, and their persistence in the environment.