Emulsive liquid-liquid microextraction using deep eutectic solvents for the determination of sulfonamide antibiotics in urine samples by high-performance liquid chromatography.

An emulsive liquid‑liquid microextraction (ELLME) technique based on deep eutectic solvents (DES) was developed for the extraction of three sulfonamide antibiotics (SAs) in canine and feline urine, followed by their determination using high‑performance liquid chromatography (HPLC) with a diode array detector (DAD). The DES synthesized from thymol and hexanoic acid was used as an extractant to form an emulsion with water for the efficient extraction of SAs. Without using auxiliary instruments or chemical reagents, the emulsion undergoes spontaneous demulsification upon static standing. No auxiliary equipment, such as vortex mixers, ultrasonic baths, or centrifuges, is required for sample pretreatment. This simplifies operational procedures and shortens the extraction time. The linear range is 0.005-0.5 mg L-1, with detection and quantitation limits of 0.002 and 0.005 mg L-1, respectively. The extraction recovery ranges from 85.3 % to 97.2 %, with a relative standard deviation <2.7 %. Seven evaluation tools were employed to assess the greenness and practical applicability of the analytical procedure. This simple and eco-friendly DES-ELLME-HPLC-DAD method provides a novel and reliable technical strategy for rapid screening and accurate quantification of veterinary drugs in urine samples.