SPECTROPHOTOMETRIC STUDIES ON PROTOLYTIC EQUILIBRIA OF 3 FORMS OF VITAMIN-B6 IN AQUEOUS AND AQUEOUS-ORGANIC SOLUTIONS

UV electron absorption spectra of three various forms of vitamin B6 we re recorded within the whole range of pH and used to evaluate the acid ic dissociation constants of pyridoxol (PN), pyridoxal (PL) and pyrido xamine (PM). The effect of three organic solvents (methanol, ethanol a nd dioxane) on the equilibrium beetwen various ionic forms of PN, PL a nd PM was examined. It was found that in neutral aqueous solutions, th e zwitter ion form is most probable, while in organic solvents the neu tral molecule predominates, and its content depends on the vitamin B-6 form and on the solvent used. In the mixture containing 92 % of dioxa ne, PM exists in the form of a neutral molecule, while in the mixture containing 92 % of methanol the percentage of this form is 60.24 %.