Carbon dioxide-switchable hydrophilicity-assisted lighter-than-water deep eutectic solvent-based liquid-phase...

Triazine herbicides are widely used agricultural chemicals with high environmental persistence and potential ecotoxicological hazards, necessitating sensitive, precise, and cost-effective analytical methods for their monitoring in water matrices. In this work, a new carbon dioxide-switchable liquid-phase microextraction technique was introduced, leveraging the reversible hydrophilicity transition of an aromatic amine-based deep eutectic solvent for the efficient extraction of simazine, atrazine, and terbutryn from aqueous samples. The menthol : 4-amino-1-naphthol deep eutectic solvent was selected as the optimal extractant due to its favorable switchable behavior, low viscosity, and strong affinity for triazines through π-π, hydrogen bonding, and hydrophobic interactions. Following CO₂-induced phase switching and ultrasonication-assisted coalescence, the final organic phase was directly injected into a gas chromatograph equipped with a flame ionization detector. Under optimum conditions, the proposed method provided acceptable extraction recoveries (66-74%) and high enrichment factors (641-719), with low limits of detection (0.17-0.31 ng mL^-1) and satisfactory intra- and inter-day precisions (relative standard deviations ≤7.1%). Linear calibration curves were obtained over a concentration range of 1-500 ng mL^-1, with coefficients of determination ≥0.995. The method was successfully validated by analyzing real environmental water samples, including river water, tap water, surface water, groundwater, and dam water, with spiked recoveries ranging from 83% to 106%, confirming its robustness in these samples. The samples were free of the analytes. Notably, the procedure required no additional cleanup or solvent evaporation steps and consumed only 130 µL of a biodegradable, low-toxicity deep eutectic solvent, aligning well with the principles of green analytical chemistry.