The use of specific additives in order to change some physical-chemical properties of different organic compounds is a relevant research topic. The possibility of modifying the polarities of organic solvents can be an important tool to solve certain separation processes. In this context, we have studied the influence in acetonitrile polarity by the addition of small quantities of ionic liquids based on imidazolium cations. The use of ionic liquids as additives can be an efficient mechanism for the modification of organic solvent polarities as well as to open new perspectives in chemical sciences.