THEORATICAL CALCULATION OF SOME PARAMETERS OF 3 KINDS OF EDIBLE PIGMENTS RELATING TO THEIR ELECTROCHEMICAL BEHAVIORS AND THEIR EXPERIMENTAL VARIFICATION

Enthalpy (Hm) and entropy (Sm) of 3 edible pigments,tartrazine,sunset yellow and ponceau 4R,were calculated theoratically by quantum theory with their reductive potentials appeared at -0.969,0.901 and -0.854 V (vs.Ag/AgCl/Cl) respectively.The mechanism of electrocatalysis of agar toward the pigments was discussed.Electrochemical behaviors of the 3 pigments at the glassy carbon-agar electrode were studied by cyclic voltammetry,and their reduction peaks were observed at -1.064,0.910 and -0.882 V (vs.Ag/AgCl/Cl) which were quite close to their theoratical values.