## 3 Results and Discussion  
### Choosing an Appropriate IL  
Previous studies on the use of ILs as solvents for biomaterials have shown that imidazolium ILs can dissolve various types of biomacromolecule [41]. It was also reported that imidazolium ILs containing a carboxylic acid anion have low melting points, low viscosities, and high hydrogen-bonding-acceptor abilities, and these properties increase the dissolution of plant matter [42]. The IL structure affects its physical and chemical properties, which might affect the extraction efficiencies of target analytes. The anion is considered to be the factor that most influences the properties of ILs [43]. 1-Butyl-3-methylimidazolium-based ILs with the same concentrations but with six different anions (Br\({}^{-}\), Cl\({}^{-}\), BF\({}_{4}\)\({}^{-}\), ClO\({}_{4}\)\({}^{-}\), HSO\({}_{4}\)\({}^{-}\), and NO\({}_{3}\)\({}^{-}\)) were used in UMASDE to identify the best IL and assess its performance in the IL-UMASDE of CPT, HCPT, VCS-LT, and EOs from _Camptotheca acuminata_ fruits. The results (Figure 4a) show that the yields of CPT, HCPT, and VCS-LT were anion-dependent and the yields obtained using [C\({}_{4}\)mim]Br were higher than those using other ILs. The yield primarily depends on the ability of the IL to dissolve cellulose in plant cells. The ability of an IL to dissolve cellulose depends on its ability to disrupt the extensive network of inter- and intra-molecular hydrogen bonds and form new hydrogen bonds between carbohydrate hydroxyl protons and the IL anions; it also depends on the strengths of interactions such as \(\pi\)-\(\pi\) and ion/charge-charge interactions [44; 45; 46]. However, there were no significant differences among the EOs yields (\(p>0.05\)). Br\({}^{-}\) was therefore chosen as the IL anion for extracting CPT, HCPT, VCS-LT, and EOs from _Camptotheca acuminata_ fruits.  
The alkyl chain length affects the water miscibility of an IL, and this can affect the extraction efficiency [47]. 1-Alkyl-3-methylimidazolium ILs containing the same anion, i.e., Br\({}^{-}\), but with alkyl chains of different lengths (ethyl to decyl) in the cation, were used in UMASDE to study the effect of the alkyl chain length. The results (Figure 4b) show that the cation alkyl cla  
Figure 4: Effects of IL anions (**a**) and cations (**b**) and concentration of [C\({}_{8}\)mim] Br (**c**) on yields of CPT, HCPT, VCS-LT, and EOs.  
affects the yields of the target compounds. This may be related to the solubilities of alkaloids and glycoside compounds in the extraction solvent. The yields of CPT and HCPT increased with increasing alkyl chain length from ethyl to octyl, but when the alkyl chain length was more than eight carbons, the yields of CPT and HCPT decreased. Thus, the highest yields of CPT and HCPT were obtained using [C\({}_{\textrm{s}}\)mim]Br. The highest VCS-LT yield was obtained using using [C\({}_{\textrm{4}}\)mim]Br, but the yield was not significantly different from that using [C\({}_{\textrm{s}}\)mim]Br (\(p>0.05\)). In addition, the EOs yields were no significant differences (\(p>0.05\)) using the ILs with alkyl chains of different lengths. Based on these results, [C\({}_{\textrm{s}}\)mim]Br was considered to be the best IL for use in further experiments.