Disclosed herein is a method comprising: (a) adding an aqueous solution comprising a quaternary ammonium salt to an organic solvent in a vessel under an inert atmosphere, thereby forming a first mixture comprising the quaternary ammonium salt and the solvent; and (b) mixing the first mixture at a temperature and for a time sufficient to remove water and a portion of the solvent from the first mixture, wherein the mixing is performed in an inert atmosphere and the temperature is less than the decomposition temperature of the quaternary ammonium salt.