Multiresidue analysis of quinolones and fluoroquinolones in soil by ultrasonic-assisted extraction in small columns and HPLC-UV

In this work, a new and simple analytical methodology for the simultaneous analysis of several quinolones (cinoxacin, oxolinic acid, nalidixic acid and flumequine) and fluoroquinolones (norfloxacin, enrofloxacin, enoxacin, ciprofloxacin and danofloxacin) in soil samples is presented. The method is based on the extraction of these analytes by an ultrasonic-assisted extraction in small columns and their subsequent quantification by HPLC using UV detection. The observed strong sorption of quinolones and fluoroquinlones to soil together their different acid-base properties made necessary an exhaustive optimisation of the extraction step. The optimum extraction procedure, based on the formation of antibiotic-Mg(II) complexes, allowed to desorb and quantitatively extract both groups of antibiotics in a single step, which was not possible by using conventional organic solvents. The proposed method was validated and the limits of detection achieved were in the low μg g⁻¹ concentration range proving its suitability for the determination of quinolones and fluoroquinolones in soil samples at realistic environmental concentration level.