In this study, octanoic acid (OA) was used as an extraction solvent for the pre-concentration and determination of three antibiotic drugs (levofloxacin, metronidazole, and tinidazole) in urine samples. To extract the antibiotic drugs, a green solvent was used as the extraction solvent in the continuous sample drop flow microextraction method, followed by a high-performance liquid chromatography photodiode array detector. According to the findings, the present study offers an environmentally friendly analytical method with a high capacity for the microextraction of the antibiotic drugs at very low concentrations. The calculated detection limits were 6.0–10.0 µg/L and the linear range was found between 20 and 780 µg/L. The proposed method showed excellent repeatability with the RSD values ranging from 2.8 to 5.5%. The relative recoveries were between 79.0 and 92.0% in the urine samples with spiked levels of 40.0–100.0 µg/L for metronidazole and tinidazole, and 100.0–200.0 μg/L for levofloxacin.

In this study, we report the synthesis and application of a novel three-component deep eutectic solvent (DES) as a promising solvent for the extraction of antibiotics from wastewater and urine. The new DES is a mixture of choline chloride, octanoic acid and ethyl benzoate at a ratio of 1 : 20 : 13, which was employed as a solvent in the extraction of several antibiotics including metronidazole, tinidazole and levofloxacin from wastewater and urine samples using continuous sample drop flow microextraction (CSDF-ME) followed by HPLC analysis. Several characterization methods including FTIR, H-NMR and C-NMR were employed to identify and confirm the formation of the synthesized DESs. The results confirmed that the new DES could be used for reliable determination of the studied antibiotics by CSDF-ME-HPLC with limits of detection in the range of 3.0–6.0 μg L−1. The calibration curves were linear between 12.0 and 780.0 μg L−1, and repeated readings with the RSD% values ranging from 1.85% to 4.95% were obtained. The relative recoveries were between 84% and 115% for the water samples spiked with 12.0–100.0 μg L−1 metronidazole and tinidazole, and 24.0–200.0 μg L−1 levofloxacin.