In situ formation of hydrophobic deep eutectic solvents for liquid-liquid microextraction of neonicotinoid...

Accurate quantification of neonicotinoids (NEOs) in complex water and tea infusion samples is crucial for environmental risk assessment and human exposure evaluation. However, traditional sample pretreatment methods are often time-consuming, labor-intensive, and rely heavily on large volumes of toxic organic solvents. In this study, an innovative in situ deep eutectic solvent (DES)-based liquid-liquid microextraction (LLME) method was developed for the preconcentration of NEOs. Conductor-like Screening Model for Real Solvents (COSMO-RS) was employed to screen suitable hydrogen bond donors as extractants. The extraction mechanism relies on stable hydrogen bonding interactions between the target analytes (acting as hydrogen bond acceptors) and the hydrogen bond donor, hexyl 4-hydroxybenzoate. The optimized LLME procedure employs 10 mL aqueous sample, 150 mg hexyl 4-hydroxybenzoate, and 120 s vortex mixing. Compared with conventional extraction method, this approach significantly reduces sample volume to 10 mL, eliminates volatile organic solvents, simplifies the workflow, and completes sample preparation in < 20 min. In combination with high-performance liquid chromatography (HPLC), the proposed method enables sensitive simultaneous determination of six NEOs, with limits of detection (LODs) ranging from 0.390 to 3.165 μg/L, recoveries of 81.61-123.04%, and relative standard deviations precision of 2.32-16.13%. The developed in situ DES-LLME method, combined with HPLC, provides a rapid, sensitive, and practical approach for monitoring NEOs in aqueous environments, showing considerable potential for applications in environmental surveillance and human exposure assessment.