Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids

© 2014. This is the accepted manuscript of the following article: Lago, S., Rodríguez, H., Arce, A., & Soto, A. (2014). Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids. Fluid Phase Equilibria, 361, 37-44. doi: 10.1016/j.fluid.2013.10.036 Citrus essential oils have numerous applications in multiple sectors, including food, drink and personal care industries. Although mainly constituted by terpenes, the appealing characteristics of citrus essential oils are due to oxyterpenes and other derived oxygenated compounds. In fact, the presence of terpenes in the essential oil may lead to instability or loss of quality. Therefore, concentration of the oil in its oxyterpene compounds by removal of terpenes is desirable. The techniques currently in use for deterpenation of essential oils present a series of issues. In the search for better deterpenation processes, here the use of ionic liquids as solvents in liquid-liquid extraction is explored. In particular, the ionic liquids 1-ethyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium acetate are investigated for their extraction of oxyterpene from a modelled citrus essential oil composed of limonene (terpene) and linalool (oxyterpene). The choice of the ionic liquids, in addition to other complementary characteristics, was based on a rationale of potential interactions that can be created preferentially with the linalool. The results show a great performance of these acetate-based ionic liquids, as compared to any other ionic or molecular solvent tested to date, for the concentration in oxyterpenes of the citrus essential oil The authors acknowledge the Ministry of Economy and Competitiveness of Spain for financial support through project CQT2012-33359 (including European Regional Development Fund advanced funding), and through the Ramón y Cajal programme (H.R.) SI