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In recent years, there has been a growing interest in plant pigments as readily available
nutraceuticals. Photosynthetic pigments, specifically chlorophylls and carotenoids, renowned for their
non-toxic antioxidant properties, are increasingly finding applications beyond their health-promoting
attributes. Consequently, there is an ongoing need for cost-effective methods of isolation. This study
employs a co-precipitation method to synthesize magnetic iron oxide nanoparticles. Scanning electron
microscopy (SEM) coupled with energy dispersive spectrometry (EDS) confirms that an aqueous
environment and oxidizing conditions yield nanosized iron oxide with particle sizes ranging from 80
to 140 nm. X-ray photoelectron spectroscopy (XPS) spectra indicate the presence of hydrous iron oxide
FeO(OH) on the surface of the nanosized iron oxide. The Brunauer–Emmett–Teller (BET) surface
area of obtained nanomaterial was 151.4 m2 g−1, with total pore volumes of pores 0.25 cm3 g−1 STP.
The material, designated as iron oxide nanoparticles (IONPs), serves as an adsorbent for magnetic
solid phase extraction (MSPE) and isolation of photosynthetic pigments (chlorophyll a, lutein) from
extracts of higher green plants (Mentha piperita L., Urtica dioica L.). Sorption of chlorophyll a onto
the nanoparticles is confirmed using UV–vis spectroscopy, Fourier transform infrared photoacoustic
spectroscopy (FT-IR/PAS), and high-performance liquid chromatography (HPLC). Selective sorption
of chlorophyll a requires a minimum of 3 g of IONPs per 12 mg of chlorophyll a, with acetone as the
solvent, and is dependent on a storage time of 48 h. Extended contact time of IONPs with the acetone
extract, i.e., 72 h, ensures the elimination of remaining components except lutein, with a spectral
purity of 98%, recovered with over 90% efficiency. The mechanism of chlorophyll removal using
IONPs relies on the interaction of the pigment’s carbonyl (C=O) groups with the adsorbent surface
hydroxyl (–OH) groups. Based on molecular dynamics (MD) simulations, it has been proven that the
selective adsorption of pigments is also influenced by more favorable dispersion interactions between
acetone and chlorophyll in comparison with other solutes. An aqueous environment significantly
promotes the removal of pigments; however, it results in a complete loss of selectivity
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