pH-Regulated Reversible Phase Transition of Natural Deep Eutectic Solvents and Its Application in the Extraction of...

Fluorinated liquid crystal monomers (FLCMs) are widely used in various electronic materials owing to their outstanding optoelectronic properties. However, their persistence, bioaccumulation, and toxicity, such as endocrine disruption, in the environment have rendered them emerging contaminants of significant concern. Switchable natural deep eutectic solvents (SNADESs) are prepared from natural compounds and their metabolites. These solvents possess the characteristics of green solvents while overcoming many limitations of conventional organic solvents, and have thus been widely adopted in the analysis and detection of environmental pollutants. In this study, a pH-SNADES was utilized as the extraction medium. Combined with ultrasound-assisted homogeneous liquid-liquid microextraction, a method for the extraction of FLCMs from environmental water samples was established, and the target analytes were qualitatively and quantitatively determined by gas chromatography-mass spectrometry. The results demonstrated that five of these compounds exhibited excellent linearity in the range of 0.5-500 ng mL^-1, while the other two (4-(3,4-difluorophenyl)-4'-pentyl-1,1'-bi(cyclohexyl) and 3,4,5-trifluoro-4'-(4-pentylcyclohexyl)biphenyl) showed linearity in the range of 1-500 ng mL^-1, with limits of detection ranging from 0.001 to 0.167 ng mL^-1 and limits of quantification ranging from 0.003 to 0.556 ng mL^-1. Applied to real water samples, the method yielded spiked recoveries of 80.79%-125.42%, relative standard deviations of 0.09%-5.14%, and enrichment factors of 8-26, with its greenness and applicability further validated by three greenness assessment tools. The proposed method is efficient, environmentally friendly, and features mild reaction conditions and simple operation, providing technical support for the detection of FLCMs in environmental water samples.