(679h) Binary Diffusion Coefficients of Phenolic Compounds in Subcritical Water Using Chromatographic Peak Broadening Technique

Flavonoids are polyphenolic compounds present in plants and are applied in food and pharmaceutical industries due to their human health benefits. Extraction of the phenolic compounds from plant matrices are both solubility and diffusion rate limited. The solubility of the phenolic compounds in subcritical water was measured by our research group using a dynamic flow apparatus [1]. The binary diffusion coefficients of these phenolic compounds in water at infinite dilution as a function of temperature can be measured using the Taylor ? dispersion method. It was found that the infinite dilution binary diffusion coefficients of these phenolic compounds in water increased exponentially with an increase in temperature. The average diffusion coefficients of the phenolic compounds increased from 2.18*10^(-9) m2/sec at 298.15 K to 6.26*10^(-9) m2/sec at 413.15 K. Due to the thermal degradability of the phenolic compounds, this method could not be used to measure the effective diffusion coefficients of certain phenolic compounds at temperatures > 100 C. The infinite dilution binary diffusion coefficients of the phenolic compounds in water were correlated as a function of temperature and viscosity. Stokes Law-based equations were used to predict the binary diffusion coefficients of the selected phenolic compounds in water as a function of temperature and compared with the measured values. It was found that there was a difference between the predicted and the experimental values that can be attributed to the validity of the assumptions made by the Stokes-Einstein model in calculating binary diffusion coefficients of such phenolic compounds.

1.Srinivas, K., King, J. W., Howard, L. R. and Monrad, J. K., 2010, Determination of solubility of quercetin and quercetin dihydrate in subcritical water using a dynamic flow technique, J. Food Eng., in press, DOI: 10.1016/j.jfoodeng.2010.04.001.