How pure are Ionic Liquids?
What exactly is purity? Most people would define purity by the actual content of the desired compound expressed in weight percent. This already is not an easy thing to do with Ionic Liquids. As salts they intrinsically consist of two compounds, an cation and an anion. For example a sample of EMIM CI might contain 5 w% of EMIM HSO4 as impurity. This means the Ionic Liquid is 100 w% pure in terms of the cation EMIM and 95 w% pure in terms of the anion chloride. Weight % is only one of many possible definitions of purity. A catalysis chemist would define purity as being free of any coordination species, like halides which deactivate the metal by formation of stable complex compounds. An electrochemist would define purity by having no oxidisable impurities which narrow down the electrochemical window. An engineer might prefer not to have impurities that affect the viscosity and finally the end user will define purity as being free of residual potentially toxic alkylating agents. These exam
