New approach for determination of flumequine and oxolinic acid in aqueous samples by ionic liquid-based dispersive liquid-liquid microextraction and high-performance liquid chromatography-fluorescence detection

A rapid and sensitive analytical method for the determination of oxolinic acid and flumequine in aqueous samples based on dispersive liquid-liquid microextraction using ionic liquids (ILs) was developed. Based on the structural properties of the antibiotic agents studied, two ILs with different functionalities were required: ethyl-dimethyl-(2-methoxyethyl) ammonium tris(pentafluoroethyl)trifluorophosphate ([MOEDEA][FAP]) for extraction and 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIM][BF₄]) to adjust the polarity of the medium. The significant experimental factors involved in DLLME were identified and optimized using the experimental design methodology. A Plackett-Burman design was initially used for screening, and a central composite design was used for optimization. The optimized method exhibited good precision, with relative standard deviation values of less than 5 % and limits of detections on the order of 0.1 and 0.3 ng mL^-1 for the two drugs. The enrichment factors for both antibiotics were 13-3 fold. The proposed method was applied to the analysis of the two antibiotic in spiked surface, river, and wastewater samples.