Diverse roles, advantages and importance of deep eutectic solvents application in solid and liquid-phase microextraction techniques - A review

Deep eutectic solvents (DESs) are an emerging class of promising green solvents used as an alternative to traditional organic solvents in various scientific fields. The high biodegradability, biocompatibility, ecofriendliness, tunable properties, and presence of active groups in DESs make them the preferred solvent in a variety of solid- and liquid-phase microextraction techniques. Aside from these benefits, the use of DESs in microextraction techniques results in increased selectivity, extraction efficiency, recovery, analyte stabilization capability, and detection compatibility. Furthermore, the ease of preparation, low cost, readily available components, separation, and applications for a wide range of samples drew significant attention. Based on these benefits, the chemists investigate the application of DESs in separation science for various roles. Based on the advantages of DESs in separation science, this review investigates and describes the various roles of DESs, including sorbent functionalization, desorption solvent, dispersing solvent, reaction media, extraction solvent, solvent for supported liquid membrane (SLM), and acceptor phase in various solid- and liquid-phase microextraction techniques for a variety of matrices, including food, water, soil, plants, beverages, medicinal supplements, and biological samples. Aside from the numerous advantages, the use of DESs for various roles in sorbent-based microextraction techniques reduces extraction performance due to variable complex interaction with the analyte, instability in extreme pH and high-temperature conditions, and insufficient analyte solubility. Furthermore, some physiochemical properties of DESs, such as viscosity, conductivity, and leakage into sample and acceptor solvents, limited their use in membrane-based microextraction methods. Future research should concentrate on developing comprehensive models that accurately describe the physiochemical properties of DESs and their intended role in microextraction techniques. The authors also suggest stabilizing agents in conjunction with DESs to improve extraction stability.