A stir-bar adsorbent of polydopamine-coated melamine sponge incorporating MIL-125 for the extraction of estrogens in milk.

Estrogens are used to increase milk production but can accumulate in the human body, eventually causing adverse effects. To extract estrogens from milk, a melamine sponge stir bar adsorbent was fabricated in a dual-polymer functionalization process, using polydopamine (PDA), and polyvinyl alcohol (PVA) combined with MIL-125 (MS-PDA@PVA-MIL-125). PDA introduced additional hydroxyl and amino groups to the adsorbent surface, increasing the number of active sites available to the target analytes. PVA acted as a binder to anchor MIL-125 into the composite structure. MIL-125 was employed as the active adsorption material, significantly enhancing the extraction efficiency of estrogens through hydrogen bonding, hydrophobic interaction, and π-π interaction. The composite adsorbent extracted estradiol, ethinyl estradiol, estrone, and hexestrol from milk samples in a stir bar sorptive extraction (SBSE) procedure. The extracted estrogens were determined by high-performance liquid chromatography coupled with diode-array detector. The developed method demonstrated good linearity from 1.50 to 100 μg L⁻¹ with a limit of detection of 0.50 μg L⁻¹. Recoveries from spiked milk samples were in the range of 80 to 104%, with RSDs less than 6%. This innovative design provides high extraction efficiency, simple preparation, self-stirring capability, cost-effectiveness, and good environmental friendliness.