NOVELTY - Ionic conduction includes providing a quat. ammonium compound, and causing the quat. ammonium compound to conduct ionically.    USE - For ionic conduction useful for coating a surface, a fuel cell, coating composition in the form of a paint, forming eutectic liquid, plasticized polymeric material, lubricant composition, and selectively absorbing a substance from a sample (i.e. fuel) of mixed composition, which is performed as part of an analytical separation process i.e. chromatographic technique (claimed), such as gas chromatography or liquid chromatography technique.    ADVANTAGE - The ionic liquid is very stable and possesses low or zero vapor pressure. The use of ionic liquid quaternary ammonium compounds as plasticizers can address the problems of slow evaporation of prior art plasticizers that can lead to polymeric materials becoming brittle and exhibiting cracking as they become older; and is particularly beneficial in polymers that need to have a long working lifetime.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of dissolving a substance including providing a liquid quat. ammonium compound; and contacting the substance with the liquid quat. ammonium compound so that the substance is dissolved in the liquid quat. ammonium compound;    (2) a method of coating a surface including contacting a surface with a composition including a liquid quat. ammonium compound to form a coating;    (3) a structure including a porous substrate and quat. ammonium compound located in the pores of the porous substrate;    (4) a liquid quat. ammonium compound having a substance dissolved in it;    (5) a method of forming eutectic liquid including providing a quat. ammonium compound; and mixing the quat. ammonium compound with a substance to produce eutectic liquid; and    (6) a method of selectively absorbing a substance from a sample of mixed composition including contacting the sample with an ionic liquid quat. ammonium compound to selectively absorb the substance.