“…The surfactants were analyzed with respect to water content, melting point, chain length, purity, and counterion purity by HPLC, NMR, and TGA/DSC (15,16). All surfactants (except octadecylpyridinium chloride) were highly purified at the Max Planck Institute of Colloids and Surfaces, Berlin, Germany, by employing the Lunkenheimer method (17,18). Due to its high surface activity, octadecylpyridinium chloride cannot be purified by this method and was used in the recrystallized form.…”