Evaluation of fatty acid/alcohol-based hydrophobic deep eutectic solvents as media for extracting antibiotics from environmental water

Fatty acid/alcohol-based hydrophobic deep eutectic solvents (DESs) have been considered to be eco-friendly alternatives to replace conventional hydrophobic organic solvents (i.e., halogenated solvents). These novel eco-friendly solvents are applied in the extraction and determination of two antibiotics (levofloxacin, LOF; ciprofloxacin, COF) in environmental water by liquid-liquid microextraction (LLME). Two different families of hydrophobic DESs, one based on fatty acids and the other on fatty alcohols, were prepared and applied as a microextraction solvent. The study results showed that 1-octanol/ tricaprylylmethylammonium chloride-based DES (DES-14) had the best extraction efficiency. The vortex-assisted method exhibited better extraction efficiency than the heating, ultrasound, and microwave auxiliary methods in LLME. The main factors affecting the vortex-assisted LLME were optimized statistically using the Box-Behnken design (BBD) combined with response surface methodology (RSM). The optimal conditions for LOF and COF were as follows: 14:174 L DES, 5.7 min vortex-assisted time, and 8.7% NaCl, w/v. Under these conditions, hydrophobic DES-based LLME was established for extraction and determination LOF and COF from environmental water, and the extraction recoveries of LOF and COF exceeded 94.8%. The proposed hydrophobic DES-based LLME method provides high precision, good linearity, acceptable limit of detection (LOD) and limit of quantification (LOQ), and satisfactory recoveries for the targets. These results support the potential of this method as a new type of extraction medium to replace conventional hydrophobic organic solvents in various applications.