Sample preparation using deep eutectic solvents in combination with nanomaterials in analytical procedures: A review

Background: Sample preparation can be a critical stage of analytical procedures that profoundly influences their performance, environmental impact, and overall efficiency. While nanomaterials have revolutionized sample preparation owing to their high surface area-to-volume ratios, tunable surface chemistry, and enhanced adsorption capacities, limitations persist. Researchers have ushered in a new era of efficient sample preparation methodologies that could overcome the limitations of nanomaterials by introducing deep eutectic solvents (DESs), which have unique advantages such as low volatility and toxicity, biodegradability, and tunability. Results: This review comprehensively explores the integration of DESs into nanomaterials in sample preparation methods. The review begins with a brief review of the different types of sample preparation techniques where DESs in combination with nanomaterials are used, including solid-phase extraction, solid-phase microextraction, and liquid-phase microextraction. The review then delves into different classes of nanomaterials depending on the functions of the DESs, that is, the modifier of nanosorbent, desorption or extraction solvent from nanosorbents, and carrier liquid in nanofluid. It further examines the applications of those nanomaterials to the quantitative analysis of a wide range of analytes within complex matrices. Finally, several challenges and concerns are discussed, including the stability, sustainability, and environmental impact of the materials, as well as the design of task-specific DESs. Significance: Unlike previous reviews on DESs used as extraction solvents, this work is the first review of the nanomaterials in which DESs with diverse roles are involved. While addressing the challenges is crucial, the advantages and opportunities offered by the DES-based nanomaterials warrant further investigation for future development in sample preparation.