Ionic Liquids as Promising Functional Materials for the Microextraction of Steroid Hormones

Prospects for the use of imidazolium ionic liquids (ILs) as extractants of sex steroid hormones (estrogens and androgens) in microextraction methods (dispersive liquid–liquid microextraction, DLLME, and magnetic solid-phase microextraction, mSPME) are identified. The key parameters of DLLME using C6MImNTf2 ionic liquid that affect extraction efficiency are optimized using the design of experiments technology. High recoveries (88–99%) are achieved. An approach of dynamic IL immobilization on the surface of magnetic nanoparticles (MNPs) for the extraction of steroids under mSPME conditions is proposed. Two types of MNP pre-coating are studied: hydrophilic based on silica and hydrophobic with oleic acid. The capabilities of C8MImBF4 ionic liquid as a MNP surface modifier for the efficient extraction of steroids are revealed. Optimum conditions provided high degrees of recovery (83–97%), with an exception of estriol (60%). The limits of detection are 0.26–1.29 ng/mL. Limitations of the method related to the partial removal of IL from the surface of NPs are revealed; they reduce the reproducibility of the results for estriol.