Abstract

The fluorescence quenching of gelatin with tannic acid was studied, and the reaction mechanism was analyzed by the Stern-Volmer equation. The number of binding sites, the binding constant, the thermodynamic functions of the reaction between gelatin and tannic acid at different temperatures were calculated. The results show that the fluorescence quenching of the gelatin with tannic acid is static quenching and that the reaction occurs when both the gelatin and the tannic acid are at ground state. The non-fluorescing complex compound is formed by hydrophobic interactions. The standard molar enthalpy (ΔHmθ) in the reaction is 58.7 KJ•mol-1 and considered as a constant for small temperature changes. The standard molar entropy values (ΔSmθ) are 277.4 J•mol-1•K-1, 277.4 J•mol-1•K-1 and 276.5 J•mol-1•K-1 at 29°C, 34°C and 38°C respectively. The thermodynamic functions in the reaction (ΔHmθand ΔSmθ ) indicate that the reaction between the gelatin and tannic acid is endothermal and that entropy increases in the process. The study should help to understand the tanning mechanism.