Research progress on ionic liquid-functionalized magnetic Fe<sub>3</sub>O<sub>4</sub> nanomaterials in sample pretreatment- chromatographic analysis

The analysis of complex sample matrices， such as environmental samples， food commodities， and biological specimens， requires sophisticated pretreatment methods. These techniques are fundamentally critical for isolating and enriching analytes of interest， thereby substantially enhancing the sensitivity， accuracy， and efficiency of subsequent analytical procedures. The judicious selection of adsorbent materials represents the pivotal element in achieving effective pretreatment. In recent years， ionic liquid-functionalized magnetic Fe₃O₄ nanoparticles （IL-Fe₃O₄ NPs） have garnered significant attention as highly promising materials within this domain. Their potential arises from an exceptional combination of properties： outstanding chemical and colloidal stability， high adsorption capacity， abundant surface active sites， superior solvation capabilities for diverse organic and inorganic compounds， potential for regeneration and reuse， and facile magnetic separation facilitated by an external magnetic field. Ionic liquids （ILs） are characterized by their structurally tailorable nature， excellent ionic conductivity， and potent dissolution capabilities. These intrinsic attributes render ILs highly effective as modifiers for Fe₃O₄ nanoparticles， either applied singularly or in hybrid composites with other functional materials. This surface functionalization fulfills two essential roles： firstly， it effectively mitigates the inherent tendency of nanoparticles towards agglomeration and provides a protective layer against oxidation； secondly， it circumvents well-documented limitations associated with bulk ionic liquids， notably their high viscosity （which impedes diffusion kinetics and mass transfer efficiency） and the practical difficulties often encountered in their separation from liquid phases. Consequently， IL-Fe₃O₄ NPs demonstrate particular utility for the efficient enrichment of trace-level analytes， such as metal ions. The resulting composite material successfully retains the advantageous core properties of the magnetic Fe₃O₄ substrate， specifically its superparamagnetic behavior （enabling rapid and efficient magnetic separation） and inherent biocompatibility. Simultaneously， it incorporates the highly desirable characteristics of ionic liquids， namely their extensive structural design flexibility and ease of chemical functionalization. The adsorption and extraction of analytes by IL-Fe₃O₄ NPs are governed by a complex interplay of multiple intermolecular forces. These encompass <i>π</i>-<i>π</i> stacking interactions， electrostatic attractions， hydrogen bonding， hydrophobic effects， and potentially coordinative interactions. This multifaceted binding capability underpins the material's demonstrated high adsorption efficiency and selectivity towards various analytes. Currently， IL-Fe₃O₄ NPs are extensively employed across a broad range of modern sample pretreatment techniques. Principal methodologies include magnetic solid-phase extraction （MSPE）， in-tube solid-phase microextraction （IT-SPME）， and pipette-tip solid-phase extraction （PT-SPE）. Furthermore， these functionalized nanoparticles exhibit excellent compatibility for integration-both in online and offline configurations-with established analytical detection platforms. This includes coupling with chromatographic techniques such as high performance liquid chromatography （HPLC） and gas chromatography （GC）， as well as spectroscopic methods including atomic absorption spectroscopy （AAS） and inductively coupled plasma mass spectrometry （ICP-MS）. The seamless coupling of IL-Fe₃O₄ NPs-based extraction with these detection systems significantly augments overall method sensitivity and analytical accuracy. As a result， these materials show considerable promise for impactful applications in critical areas such as food safety assurance， environmental contaminant monitoring， and biomedical analysis. This article systematically summarizes the synthesis methods， classifications， main extraction modes， online or offline detection techniques， and applications in sample pretreatment of IL-Fe₃O₄ NPs， while also providing an outlook on potential future exploration directions for this class of materials.