Synthesis of citric acid monohydrate-choline chloride based deep eutectic solvents (DES) and characterization of their physicochemical properties

Abstract The objective of the study was to synthesize deep eutectic solvents (DES) using choline chloride and citric acid monohydrate at different molar ratios (i.e. DES 3:1, 2:1, 1:1, 1:2 and 1:3) followed by physicochemical characterization. The DES produced were clear and homogenized liquids under a microscopic observation, and DES 1:1 was found to meet the eutectic point with the lowest melting temperature. Fourier-transform infrared spectroscopy (FTIR) analysis showed the hydrogen bond interaction between the components in DES where the wavenumbers of functional groups were shifted. Results also showed that when the molar ratio of citric acid monohydrate increased in DES, higher values of viscosity, surface tension and density were observed. It was also found that the DES produced were classified as hydrophilic DES because of their solubility in water, highly polar and most semi polar solvents. In summary, the DES synthesized was suggested to be used as a medium for the extraction of hydrophilic components from plant or animal materials.