Spectra of excess molar absorptivity of aqueous solutions of ionic liquids: Universal chromophores for aqueous electrolytes?

We devised a new data analysis methodology for Near Infrared spectroscopic data of aqueous solutions. We first isolate the non-ideal (i.e. real) part of the results as the excess molar absorptivity, epsilon(E), then define and calculate the excess partial molar absorptivity of solute, epsilon(E)(S), the effect of solute (S) on the excess molar absorptivity, epsilon(E). By using these, we learned that there are three universal chromophores in the nu(2) + nu(3) combination band of H2O in the epsilon(E) spectra of aqueous solutions of the total nine electrolytes. Furthermore, we learned from the excess partial molar absorptivity, epsilon(E)(S), we identified a specific chromophore out of three that distinguish the specific characteristics of a given solute on H2O. Here we add an evidence for the universality of three bands in epsilon(E) to include two examples of ionic liquids. In addition, using the literature data, we show that the vi overtone of H2O in NaCI - H2O and CaCl2 - H2O also have a limited number of universal chromophores at the same wave numbers in their epsilon(E) spectra. (C) 2017 Elsevier B.V. All rights reserved.