Novel ferrofluid based on hydrophobic deep eutectic solvents for separation and analysis of trace estrogens in environmental water and urine samples

A novel ferrofluid prepared from a hydrophobic deep eutectic solvent (DES) and Fe 3 O 4 @graphite composite materials was introduced as a green microextraction medium for the separation and enrichment of trace estrogens in real samples. It was found that the ferrofluid greatly improved the capacity and selectivity of target analytes, benefiting from the enrichment of both DES and Fe 3 O 4 @graphite composite materials. Using a combination of high-performance liquid chromatography–fluorescence detection (HPLC-FLD) and vortex-assisted liquid–liquid microextraction (VALLME), a new method was established for simultaneous rapid processing and accurate determination of three estrogens (estradiol [E2], estriol [E3], and ethinyl estradiol [EE2]) in environmental water and urine samples. Key parameters affecting the extraction efficiency were optimized using a single-factor approach and response surface methodology. Under optimal conditions, this method yielded a low limit of detection (1.01 ng L −1 , 3.03 ng L −1 , and 25.0 ng L −1 for EE2, E2, and E3, respectively), wide linear range (3–200,000 ng L −1 ), high enrichment factors (9.81–47.2), and satisfactory recovery (73.8–129.0%). Compared with traditional analytical techniques, this method avoids the use of volatile toxic organic extraction solvents and cumbersome phase separation operations. Graphical abstract