# Recent Applications of Deep Eutectic Solvents in Environmental Analysis
## Recent Applications of DESs in Environmental Analysis  
### Analysis of Organic Compounds in Environmental Samples  
The unique features of DESs have boosted their applications in analytical chemistry, especially as alternative extraction solvents in sample preparation. In this sense, as can be seen in Table 1[11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25], these solvents have been successfully employed for the evaluation of plastic migrants [11; 16], pharmaceuticals [12; 13; 17; 19], pesticides [14; 15; 18; 25], dyes [15], hormones [16], ultraviolet (UV)-filters [16; 21], polycyclic aromatic hydrocarbons (PAHs) [22] and explosives [24] in different environmental matrices, mainly water samples [11; 12; 13; 14; 15; 16; 17; 22; 24; 25] and to a lesser extent in soil samples [15; 24]. Among the types of DESs used with this purpose, HDESs have significantly replaced hydrophilic DESs, since they overcome the limitations for the separation of target analytes from aqueous medium [11; 12; 13; 14; 17; 18; 21; 24]. Although quasi-HDESs are prepared from medium-chain quaternary ammonium salts and medium-chain fatty acids [15; 19; 22], combinations of more than two components to form ternary DESs (TDESs) [16], as well as ChCl-based hydrophilic DESs combined with nanomaterials [25] have also been investigated as extractants of organic contaminants from environmental samples. In addition, ChCl-based DESs have also been applied to capture CO\({}_{2}\) from natural gas [20] and biomass delignification [23]. Regarding the extraction procedures, the application of DESs has taken place in various microextraction techniques including liquid-liquid microextraction (LIME) [11; 13; 15; 16; 17; 18; 21; 22] and its dispersive mode (DLLME) [12; 14; 19], assisted by vortex (VA) [11; 15; 19], ultrasounds (UA) [14; 18; 22], air cycles of pulling in/pushing out [16; 21], using a mechanical shaker (SA) [17], controlled by pH changes [13] and solidifying the floating organic droplet (SFOD) after the extraction process [16; 22], as well as in solid-phase extraction in its magnetic-micro-dispersive mode (m-\(\upmu\)-dSPE) [24; 25]. A heating and stirring extraction has also been developed [23]. Likewise, the in situ formation of DESs has been another strategy used in this field [17]. \begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline
**Sample (Amm0)** & **Analyytes** & **DES** & **Data Ratio** & **Extraction Procedure** & **Analytical Technique** & **Reeovery \%** & **LODs** & **Comments** & **Reference** \\ \hline \hline Trotated wastewater runoff, and pond water(10 mL) & 14 PLES and one adaptate & Mentholt thymol (2; 100 mL) & VA-LIME (2; 100 mL) & UPLC-QQ-MS/MS & 70-127 & 0.013-0.425 mg/L & - ‘Indent extract was 20-fold diluted with AN. & [11] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Some examples of the recent applications of DESs to the analysis of organic compounds in environmental samples. \begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Sample**}} & \multirow{2}{*}{**Analytes**} & \multicolumn{2}{c}{**DES**} & \multicolumn{2}{c}{**Extraction**} & \multicolumn{2}{c}{**Analytical**} & \multicolumn{2}{c}{**Recovery \%**} & \multicolumn{2}{c}{**LODs**} & \multicolumn{2}{c}{**Comments**} & \multicolumn{2}{c}{**Reference**}  
In this sense, an interesting example of the application of DESs as extraction solvents of organic compounds in environmental samples is the work carried out by [PERSON] et al. [12] for the extraction of three tetracyclines from various water samples using a disperser/extraction solvents mixture based on DESs. In this case, two hydrophilic DESs composed of ChCl as HBA and urea or ethylene glycol as HBDs at molar ratio 1:2, and three HDESs formed by thymol as HBA and different medium-chain fatty acids including octanoic, nonanoic or decanoic acids as HBDs at a molar ratio of 1:1, were prepared and evaluated.