Eleven experimental investigation of diffusion in gels containing immobilized cells are reviewed. The experimental data, which quantitatively express the diffusion coefficient as a function of the cell concentration, are compared with a number of well-known equations developed for mass transfer in heterogeneous media. Based on this comparison, a procedure for the theoretical prediction of effective diffusion coefficients in cell-containing gels is recommended.
Recewed 8 November 1991. m final form 4 August 1952 Abstrad. The dlffwmn of temc tons produced by t m d m o n m a dosimeter gel, constamg of a ferrous sulphate mlution and agarose gel, has been studied The diffusmn mefficrent of feme ions m the gel was found Lo be 1 91 x IO-' mz h-' 15% It was shown that the dwe image obtained with an MR ~~a n n e r delenorales due to diffusion. Thw delenoration o n be predicted with the aid of the measured diffusion coeffiaenl. It was concluded that d the m meaiuremenll (]/TI Image) of a typical depihdose dtsmbuilon are omed oui wthin 2 houn of rrradmron the diffusion wlll no1 have a significant effect on the reSUllS 1. In .roduciiou
The accuracy and precision of holographic interferometry as a method to measure diffusion coefficients in gels are investigated both experimentally and theoretically. The standard deviations in the experimentally determined diffusion coefficient for ethanol in 4% (w/v) agarose gel were 3.3% for diffusion into the gel and 6.1% for diffusion out of the gel. These are in good agreement with the standard deviations obtained using Monte Carlo simulations. Systematic errors derived from an assumption of constant diffusion coefficients were also investigated.
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