Novel deep eutectic solvents (DESs) were prepared from tetrabutylammonium chloride as a hydrogen bond acceptor in combination with ninhydrin as a hydrogen bond donor. The physical properties of the prepared DESs were investigated at different temperatures, and the results of density, sound velocity, surface tension, and refractive index along with FTIR and 1H NMR analyses data to confirm their chemical structures and occurrence of hydrogen bonding interactions between the hydrogen bond acceptor and the hydrogen bond donor, which formed the DESs. The novel DESs were used as a solvent and a reagent for the qualitative and quantitative determination of alanine, glycine, leucine, and serine.
