## 3 Results and Discussion
### Extractive Capacity of DES  
The total amounts of fatty acids in the form of methyl esters that were obtained with each DES are shown in Figure 3. According to these results, the DES based on choline chloride and ethylene glycol outperformed the phases based on choline chloride and fructose. Specifically, the compositions CE1 and CE2 offered the highest extraction yields, with values of over 11.2 and 10.06 mg/g of microalgae. These extraction capacities were higher than those obtained in the absence of water (CE0). The compositions based on choline chloride and fructose (from CF1 to CF2) did not offer significant extraction capacities regarding total fatty acids, with values below 0.35 mg/g. The extraction of fatty acids from microalgae was also performed with methanol as a conventional organic solvent. The traditional solvent was able to recover a higher quantity of total fatty acids in comparison with DES, with a final value of 23 mg/g of microalgae. Although DES can only recover approximately half of the total amount of fatty acids that can be obtained with a traditional solvent, they offer additional advantages over these types of solvents, as indicated in Section 1. \begin{table}
\begin{tabular}{c c} \hline
**DES** & **Formation Temperature (\({}^{\circ}\)C)** \\ \hline CE0 & 63 \\ CE1 & 53 \\ CE2 & 60 \\ CE3 & 45 \\ CF1 & 92 \\ CF2 & 84 \\ CF3 & 73 \\ \hline \end{tabular}
\end{table} 
Table 3: Formation temperature of DES phases. Figure 2: FTIR spectra of choline chloride–fructose-based DES. Regarding the individual fatty acids obtained from microalgae with DES, in the case of the choline chloride-ethylene glycol-based CE1, the yields in the form of methyl esters were: hexadecenoic acid (30.13%), eicosapentaenoic acid or EPA (29.62%), octadecenoic acid (9.26%), hexadecenoic acid (8.54%), eicosatetraenoic acid (7.56%), octadecadienoic acid (7.47%), octadecanoic acid (3.47%), myristic acid (2.81%), pentadecanoic acid (0.47%), dodecanoic acid (0.35%), decanoic acid (0.17%), and octanoic acid (0.08%). As seen, EPA is the second most abundant fatty acid recovered from microalgae. For the choline chloride-fructose mixture CF2, the individual yields were: decanoic acid (40.1%), hexadecenoic acid (29.54%), hexadecanoic acid (10.20%), octadecanoic acid (6.10%), octadecenoic acid (4.67%), octadecadienoic acid (3.17%), myristic acid (2.49%), octanoic acid (2.15%), and dodecanoic acid (1.58%). The analysis of the capacity extraction of individual fatty acids also offers interesting results. Hexadecenoic acid was among the most abundant fatty acids recovered from microalgae. Figure 4 shows the capacity extractions of each DES for this specific fatty acid (in the form of methyl ester), obtaining the same patterns as those shown in Figure 3 for the total amount of fatty acids. This means that the choline chloride-ethylene glycol-based DES with a composition of 1:2:1 and 1:2:2 (CE1 and CE2) were able to recover the highest quantities of hexadecenoic acid, with values of 3.38 and 3.09 mg/g. Figure 4: Recovery performance of hexadecenoic acid methyl ester with each DES mixture. Figure 3: Total fatty acids extracted with each eutectic. On the other hand, although the DES phase based on choline chloride and fructose yielded low recovery amounts of total fatty acids, such phases could be useful for the selective extraction of short-chain fatty acids. As can be seen in Figure 5, the DES mixture based on choline chloride and fructose, especially the composition CF2, could recover higher amounts of decanoic acid, with a total amount of 0.14 mg/g of microalgae. These yields were higher in comparison to the DES based on choline chloride and ethylene glycol for this specific fatty acid. The results shown in Figures 3 and 4 highlight the effect of water content on the extractive capacity of DES. The extraction capacity of the DES based on choline chloride and ethylene glycol is higher in the presence of water.