Flexible natural deep eutectic solvent extraction coupled with precolumn-switching HPLC-FLD to analyze fluorescent whitening agents in diverse sample matrices for migration study.

This study proposes a novel analytical approach coupling of natural deep eutectic solvent (NADES) extraction with a precolumn-switching high-performance liquid chromatography with fluorescence detection (HPLC-FLD) system for analyzing fluorescent whitening agents (FWAs) in diverse sample matrices. NADES (coumarin/thymol) provide a green alternative to conventional solvents. The automated precolumn-switching strategy overcomes the compatibility issues between DES and HPLC, preventing column contamination and maintaining separation efficiency without the need for extensive dilution of NADES prior to injection. Three NADES extraction modes were proposed: phase-reversed NADES liquid-liquid extraction, NADES liquid-solid extraction, and NADES dispersive liquid-liquid microextraction, to achieve effective FWAs analysis in blood, urine, packaging materials, cosmetics, and cosmetic simulants. Method validation shows high sensitivity, with limits of detection (LODs) as low as 0.002 μg/L and good accuracy (recoveries 88.2 %-114.4 %). The practicality and reliability of this method are confirmed through its application to real positive samples from various source. Additionally, the research investigates FWAs migration from packaging to cosmetics and simulants, which also reveals the FWAs migration from sanitary products into blood and urine for the first time. The Weibull model has been proven to effectively describe FWAs migration behavior and provides a predictive tool for long-term migration risk assessment. This work not only provides a novel, green analytical approach for FWAs but also contributes valuable data for evaluating the safety of cosmetic packaging and sanitary products.