Temperature-Induced Ionic Liquids Dispersive Liquid–Liquid Microextraction of Tetracycline Antibiotics in Environmental Water Samples Assisted by Complexation

In this study, dispersive liquid–liquid microextraction (DLLME) combined with ultra high pressure liquid chromatography (UHPLC)–tunable ultraviolet detection (TUV), was developed for pre-concentration and determination of trace levels of tetracyclines, including 4-epitetracycline, 4-epichlortetracycline, doxycycline, chlortetracycline oxytetracycline, tetracycline, 4-epianhydrotetracycline and anhydrotetracycline, in aqueous samples. La (III) was used as the chelating agent to form a hydrophobic complex compound with tetracyclines, followed by extraction with ionic liquids. Some important parameters that may affect extraction efficiencies were examined and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.1–200 μg L−1, with correlation coefficients (r2) >0.992. The limits of detection and quantification were 0.031–0.079 and 0.10–0.26 μg L−1, respectively. The spiked recoveries of eight target compounds in river water, fishpond water and hog leachate were achieved in the range of 62.6–96.3, 58.9–94.5, 55.1–86.1%, respectively.