Solvent-free microwave-assisted extraction of fluoroquinolones from soil and liquid chromatography-fluorescence determination

Abstract

Presented hereafter is a novel method entailing solvent free microwave-assisted extraction (MAE) and HPLC equipped with Fluorimetric Detector (HPLC-FD) for the simultaneous determination at μg kg −1 concentration of eight fluoroquinolone antibiotics (FQs) (Ciprofloxacin, Danofloxacin, Enrofloxacin, Flerofloxacin, Levofloxacin, Marbofloxacin, Norfloxacin and Orbifloxacin) in agricultural soils. The extraction was quantitatively performed, in a single step, by using an aqueous solution containing Mg(II) as complexing agent, thus avoiding consumption of organic solvents. The optimal MAE conditions have been established through a chemometric approach by considering temperature, irradiation time and matrix moisture or solvent, as the most important recognized variables affecting the extraction yield. Satisfying recoveries (69–110%, spikes 0.03–0.5 mg kg −1) were gained with a single MAE cycle of 20 min, at 80 °C in 20% (w/v) Mg(NO 3) 2 solution as leaching agent. MAE-SPE recoveries at 10 μg kg −1, concentration near method quantification limits (MQLs), were in the range 60–85%. Good repeatability and within-lab reproducibility were observed (both in the range 1–16%). The applicability of the method to real samples was assessed on natural contaminated soils. Compared to ultrasonic-assisted extraction (UAE), MAE was shown to be highly competitive in terms of extraction efficacy and analysis speed.