(Deep) eutectic solvents in chromatographic and electromigration techniques

(Deep) eutectic solvents ((D)ESs) have been recognized as a promising class of designer solvents for separation science, offering unique physicochemical properties and structural versatility beyond those of conventional solvents. Their integration into chromatographic and electromigration techniques (i.e., capillary electrophoresis and capillary electrochromatography) has created new opportunities for enhancing separation performance while promoting greener analytical practices. This review provides a systematic summary of (D)ES applications in these fields, with particular attention to their diverse functional roles across different separation platforms. We critically examine the physicochemical properties of (D)ESs that drive separation efficiency, elucidate the associated mechanisms, and discuss persistent challenges and debates in the field. The discussion is structured around the specific roles (D)ESs serve within diverse separation systems, aiming to provide a clear and organized perspective on current research progress.