The infrared spectra of some vitamins in water are presented. The spectra of two forms of vitamin B6 are included and that of the Schiff base formed between pyridoxal phosphate and glycine. The spectrum of copper (L-lysine)2 is given as an example of an amino acid chelate compound in water.
Frank S. Parker, "Infrared Spectra of Vitamins, a Schiff Base, and an Amino Acid Chelate in Water," Appl. Spectrosc. 15, 96-99 (1961)