Deep eutectic solvent in magnetic solid-phase extraction of precious metals

This work highlights the potential of TOPO-based deep eutectic solvent as smart extraction media and functional coating for magnetic sorbents, enabling efficient and selective recovery of strategic metals. Magnetic nanoparticles were prepared by the one-pot interphase synthesis and functionalized with a hydrophobic deep eutectic solvent TOPO/butanol. The magnetic solid-phase extraction of precious metals was developed using the Fe₃O₄@PEG@TOPO/butanol sorbent. Quantitative recovery of Au, Pt and Pd (>95%) from hydrochloric acid solutions was achieved, as well as efficient recovery of Ru, Rh and Ir (∼70%) in the presence of chloride ion. The hybrid method based on TOPO-based magnetic solid-phase extraction, elution of the target metals with a thiourea solution, and their ICP-AES determination is proposed. The method provides linear ranges of 10-200 μg L^-1 (Au) and 20-500 μg L^-1 (Pt, Pd) with R² ≥ 0.9991, LODs of 0.05-0.12 μg L^-1, and acceptable precision (RSD < 4.9%). The practical applicability of the method and matrix tolerance has been demonstrated by analyzing the platinum ore SARM AMIS 0192 and a model spent automotive catalyst leachate. An assessment of the method's environmental friendliness is provided.