Screening of Temperature‐Responsive Deep Eutectic Solvents for Their Application in the Determination of Fluorinated Liquid Crystal Monomers in the Environmental Water

ABSTRACT Fluorinated liquid crystal monomers, owing to persistent, bioaccumulative, and toxic properties, have been detected in environmental and biological samples, posing potential hazards to the environment and humans. However, current pretreatment methods predominantly rely on volatile organic solvents, necessitating cumbersome purification and prolonged nitrogen evaporation time. Moreover, the trace distribution characteristics of fluorinated liquid crystal monomers in the environment demand pretreatment methods that combine highly selective extraction capabilities with significant enrichment efficiency. Consequently, developing efficient extraction methods is crucial for enhancing the detection of fluorinated liquid crystal monomers in the environment. Temperature‐responsive deep eutectic solvents represent a novel class of designable extraction solvents developed in recent years. Under temperature induction, temperature‐responsive deep eutectic solvents reversibly switch between polar and non‐polar states, achieving separation and enrichment effects. According to the biphenyl structure of fluorinated liquid crystal monomers, phenolic compounds were selected as precursors to prepare a series of temperature‐responsive deep eutectic solvents for extracting 15 fluorinated liquid crystal monomers from water samples. During the transition from polar to hydrophobic non‐polar states, temperature‐responsive deep eutectic solvents extract fluorinated liquid crystal monomers from water via π‐π interactions and intermolecular hydrogen bonding. Single‐factor screening identified temperature‐responsive deep eutectic solvents (M 4‐chlorophenol :M 4‐ethylphenol = 1:2) as the optimal extractant, with extraction conditions optimized using response surface methodology. Method's LOD and LOQ ranged from 0.08 to 0.30 µg/L and 0.26 to 0.98 µg/L, respectively. In analysis of surface water samples and wastewater treatment inlet/outlet samples, the spiked recovery rates of fluorinated liquid crystal monomers ranged from 70.5% ± 3.5% to 125.8% ± 1.6%, with detection concentrations spanning 0.44–2.67 µg/L. Compared to conventional methods, this approach achieves one‐step extraction without requiring purification or additional dispersing solvents. It reduces extractant consumption and shortens extraction time while maintaining high extraction efficiency, offering a novel approach for detecting fluorinated liquid crystal monomers in environmental water.