Diffusion Coefficients in Intrahollow Calcium Alginate Microcapsules

Intrahollow calcium alginate microcapsules were prepared with sodium alginate (SA) of different concentrations. Using a well-mixed and temperature-controlled vessel, the diffusivities of glucose, lactose, tyrosine, glutamic acid, lysine, and phenylalanine from bulk solution into the microcapsules were investigated and the diffusion coefficients were also calculated. The results indicate that all these substrates tested can diffuse easily through the microcapsule. The combined diffusion coefficients (D<INF>m</INF>) are 2%−12% smaller than the diffusion coefficients in pure water while the diffusion coefficients in the microcapsule membrane (D<INF>1</INF>) are 50%−94% smaller than those. In all cases, the diffusion coefficients are hardly affected by SA concentrations ranging from 8 g·L^-1 to12 g·L^-1 used in preparing the microcapsules.