In situ formation of deep eutectic solvents based dispersive liquid–liquid microextraction for the enrichment of trace phthalate esters in aqueous samples

In this work, several new in situ deep eutectic solvents (DESs) were prepared with two low toxic phenols thymol and p -cresol as hydrogen bond donors (HBDs) and three biodegradable esters 3-hydroxyhexanoate, butyl lactate and methyl salicylate as hydrogen bond acceptors (HBAs), and the in situ formation of DESs could be achieved at room temperature . Based on the in situ formation of DESs, a dispersive liquid–liquid microextraction (DLLME) method was developed to enrich four phthalate esters (PAEs) from water and beverage samples combined with gas chromatography-flame ionization detection (GC-FID). After the most appropriate type of DES was determined, the influencing factors of the in situ DES-based DLLME procedure were explored and optimized by Design of experiment (DoE). The optimized in situ DES-based DLLME approach exhibited good linearity in the range of 1–800 µg/L with determination coefficient (R 2 ) from 0.9936 to 0.9983, limits of detection (LODs) within 0.5–2 μg/L, enrichment factors (EFs) from 256.3 to 467.1 and extraction recoveries (ERs) of 51.26 %-93.42 %. Finally, the proposed method was successfully applied for the determination of PAEs in water and beverage samples contacted with plastics, and good practical applicability was presented with the spiked recoveries of 76.17 %-118.09 %.