Quinolone and fluoroquinolone residues in agricultural soils from Valencian Community (Spain)

Abstract

Fluoroquinolones (FQ) represent a major group of synthetic antibiotics, which have been widespread use during the last 15 years in human and in veterinary medicine for the treatment of bacterial diseases. Their use leads to an entry of these compounds into the environment through the excretion of unmetabolised quinolones and the disposal of unused drugs (Andreu et al. 2007). Quinolones are rather persistent with half-lives of 151 days. They interfere with bacterial DNA metabolism by inhibiting two enzymes, topoisomerase II and IV. These enzymes introduce negative super helical twists into the DNA strands. Inhibition of these reactions prevents DNA replication, repair, recombination and transposition (Pico & Andreu, 2007) For instance, in soil, most of the quinolones come from sludge soil amendments and irrigation with waste-water. The amount of quinolones in soils is of importance because of their effects on soil organisms and plants. As a result of their widespread presence, quinolones are generally introduced in monitoring programs for emerging pollutants in waters. On the contrary their determination in soils is still scarce and there is a need of analytical methods developed for it (Petrovic & Barcelo, 2007; Vazquez-Roig et al. 2010). In this study, PLE and ultrasonic extraction were compared for the extraction of eight quinolones in soil, followed by liquid chromatography coupled to triple quadrupole (LC¿QqQ-MS/MS) determination. Both extraction procedures combined with the chromatographic method was used to determine quinolones at trace levels in soil samples taken from different agricultural areas of the eastern of Spain. Pressurized liquid extraction (PLE) and ultrasonic extraction methods were optimized. Parameters such as type of solvent, extraction time, extraction temperature and number of extractions were optimized. There were no significant differences among the two extraction methods although better extraction efficiencies were obtained when PLE was used, minimizing extraction time and solvent consumption. Both procedures were validated, obtaining limits of detection (LODs) ranging from 0.02 to 0.75 ng g¿1 and limits of quantification (LOQs) ranging from 0.07 to 2.50 ng g¿1 for the selected quinolones. Recoveries were in the range of 59¿110%, except for enrofloxacin, which was the most volatile quinolone. Finally, the method was applied to real soil samples from Southeast of Spain. Quinolone concentrations were low, and enrofloxacin, ciprofloxacion and ofloxacin were the most frequently detected analytes in the samples.