Deep eutectic solvents in chemical analysis. Opportunities and limitations

Deep eutectic solvents (DES) are a mixture of two or more components, the melting point of which is significantly lower than the melting points of the starting materials. Environmental safety, ease of preparation in the laboratory, and low cost of DES have led to the fact that they have recently found increasing use in analytical chemistry. DES are most widely used in separation and concentration methods as effective extractants for the isolation of both hydrophobic and hydrophilic analytes from various objects of analysis. However, the possibility of their application is not limited to use only as extractants. This paper presents the classification of DES according to the criterion of their stability in the aqueous phase, the possibilities and examples of the separation of analytes from liquid, solid-phase and gaseous samples into the DES phase are also considered. In addition, various schemes for the implementation of liquid microextraction based on the principles of the formation and destruction of DES and methods for their automation based on the principles of flow methods are considered. The possibility of using eutectic compounds as effective dispersants in dispersive liquid extraction has been demonstrated. The possibility of simultaneous use of eutectic solvents both as extractants and as reagents for the derivatization of analytes to convert them into an analytical form directly in the extraction process, is shown. The possibility of modification of various sorption materials with eutectic solvents for the method of solid-phase microextraction, is shown. The paper touches upon the problems and limitations associated with the use of DES in chemical analysis, as well as the main prospects for its development.