The number of studies on the solubilities of amino acids in pure ionic liquids is currently very scarce. Focusing on fundamental studies for the recovery of added-value compounds from fisheries and aquaculture discards, in this work the solubility of several amino acids in acetate ionic liquids and their mixtures with water were determined at temperatures ranging from 298.15 K to 328.15 K and atmospheric pressure. Sharing the acetate anion, solubilities were higher in the ionic liquid with 1-ethyl-3-methylimidazolium than with 1-hexyl-3-methylimidazolium cation. Increasing temperatures resulted in enhanced solubilisation. Solubilities in the ionic liquids ranked thus: Pro > OH-Pro > Lys·HCl > Ala > Gly > Cys, with an intermediate position of Arg (the amino acid most influenced by the hydrophobic environment and temperature). In the case of the mixtures with water, the ranking was Pro > Lys·HCl > Ala > Arg > OH-Pro > Gly > Cys. The van't Hoff equation adequately correlated experimental solubilities in the range of temperatures studied, and the process of dissolution was found endothermic and entropy-driven in all the cases. The ionic liquid 1-ethyl-3-methylimidazolium should be considered for the target application and the water content a design variable to analyse.

中文翻译：

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七种氨基酸在两种醋酸盐离子液体中的溶解度（298.15 K 至 328.15 K）

目前关于氨基酸在纯离子液体中溶解度的研究数量非常稀少。这项工作侧重于从渔业和水产养殖废弃物中回收附加值化合物的基础研究，在 298.15 K 至 328.15 K 的温度和大气压下测定了几种氨基酸在醋酸盐离子液体及其与水的混合物中的溶解度。共用乙酸根阴离子，具有1-乙基-3-甲基咪唑鎓离子液体的溶解度高于具有1-己基-3-甲基咪唑鎓阳离子的离子液体。升高温度导致溶解增强。在离子液体中的溶解度排序如下：Pro > OH-Pro > Lys·HCl > Ala > Gly > Cys，中间位置为Arg（受疏水环境和温度影响最大的氨基酸）。在与水的混合物的情况下，排序为Pro>Lys·HCl>Ala>Arg>OH-Pro>Gly>Cys。范特霍夫方程充分关联了所研究温度范围内的实验溶解度，并且在所有情况下都发现溶解过程是吸热和熵驱动的。应考虑目标应用中的离子液体 1-乙基-3-甲基咪唑鎓，并将水含量作为要分析的设计变量。