Oxidized multi-walled carbon nanotubes for the dispersive solid-phase extraction of quinolone antibiotics from water samples using capillary electrophoresis and large volume sample stacking with polarity switching

In this work, a new method for the determination of eleven quinolone antibiotics (moxifloxacin, lomefloxacin, danofloxacin, ciprofloxacin, levofloxacin, marbofloxacin, enrofloxacin, difloxacin, pefloxacin, oxolinic acid and flumequine) in different water samples using dispersive solid-phase extraction (dSPE) and capillary zone electrophoresis with diode-array detection was developed. Oxidized multi-walled carbon nanotubes (o-MWCNTs) were used for the first time as stationary phases for the off-line preconcentration by dSPE of the antibiotics. A 65 mM phosphate buffer at pH 8.5 was found adequate for analyte separation while large volume sample stacking with polarity switching of the analytes dissolved in water containing 10% (v/v) of acetonitrile was carried out in order to improve the sensitivity. dSPE parameters, such as sample volume and pH, o-MWCNT amount, volume and type of eluent in dSPE were optimized. Application of the developed method to the analysis of spiked Milli-Q, mineral, tap, and wastewater samples resulted in good recoveries values ranging from 62.3 to 116% with relative standard deviation values lower than 7.7% in all cases. Limits of detection were in the range of 28–94 ng/L. The proposed method is very fast, simple, repeatable, accurate and highly selective.