Deep eutectic solvent-based dispersive liquid–liquid microextraction: Principles, developments, and applications in trace analysis

Sample preparation remains one of the most critical and time-consuming steps in chemical analysis, particularly for the determination of trace-level analytes in complex matrices. Conventional extraction techniques, such as liquid–liquid extraction and solid-phase extraction, are often associated with high solvent consumption, limited selectivity, and environmental concerns. In this context, dispersive liquid–liquid microextraction (DLLME) has emerged as an efficient miniaturized technique due to its rapid extraction kinetics, low solvent usage, and high enrichment capability. However, the widespread use of toxic organic solvents in classical DLLME systems restricts its sustainability and broader applicability. To address these limitations, recent research has focused on the development of greener extraction media, particularly deep eutectic solvents (DESs), which offer tunable physicochemical properties, low volatility, and improved compatibility with green analytical chemistry principles. These alternative solvents have enabled the design of more sustainable, efficient, and selective DLLME systems.This review, after addressing the fundamental extraction mechanism of DES-based DLLME, provides an overview of approaches developed for the determination of pesticides and heavy metals, with a primary focus on the chronological development of the reported methods. The studies are summarized in terms of physicochemical properties, the types of DESs used and their component ratios, as well as their analytical applications. Methodological variations, including in-situ solvent formation, hybrid extraction techniques, and different dispersion strategies, are outlined. In addition, the types of sample matrices investigated and the analytical performance characteristics are presented in a general framework.