Green, sustainable, and eco-friendly deep eutectic solvent-based microextraction approaches coupled with instrumental techniques: advantages, limitations, and challenges

Deep eutectic solvents (DESs) represent a class of promising green solvents that have garnered significant interest from researchers across various scientific disciplines. DESs have been extensively studied in separation science for various applications. In separation science, particularly within solid-phase and liquid-phase microextraction techniques, DESs have been investigated for the extraction of various analytes. This interest is attributed to their excellent biodegradability, eco-friendly characteristics, ease of synthesis, low cost, readily available components, high extraction efficiency, presence of active functional groups, high selectivity for analytes, and tunable properties. Based on the numerous advantages of microextraction techniques, this narrative critical review provides a brief description of the classification, preparation techniques, and characterisation methods of DESs. Most importantly, this review primarily emphasises the critical discussion of deep eutectic solvents-based microextraction methods coupled with various instrumental techniques, including chromatographic techniques, atomic spectrometric techniques, and UV-vis spectrophotometric techniques. Each section examines the advantages and limitations associated with the developed methods. Furthermore, the drawbacks of deep eutectic solvent-based methods and the associated challenges in instrumental techniques are briefly evaluated. Chromatographic techniques were found to be most commonly used for the separation and quantitative analysis of pesticides and pharmaceuticals, whereas atomic spectrometric techniques are used for heavy metal analysis.