Fifteen new protic ionic liquids based on diethanolammonium (DEA) salts of carboxylic acids have been synthesized and identified using a complex of physicochemical methods (NMR, FT-IR spectroscopy, elemental, thermal analysis). The crystal structure of diethanolammonium salts of benzoic and 1-hydroxy-2-naphthoic acids was determined for the first time by XRD. A comparative analysis of the conformations of DEA cations was carried out. The effectiveness of synthesized DEA ionic liquids as buffer agents was demonstrated on ⁶⁸Ga-radiolabeling reactions with different chelators and clinically approved peptides.