Question: A diffusion cell is constructed that consists of a thin membrane (thickness 200 micro meters and area 1 cm^2) separating two solutions of identical volume (V= 10 cm^3). The donor solution contains a drug molecule of interest. The drug has a partition coefficient of 15 in the membrane. State all your assumptions and boundary conditions in the calculation.
1) If the donor solution concentration remains unchanged at 10 mg/ml. The receptor solution is maintained at a much lower concentration. The amount of drug that passes through the membrane is 6.5 mg/hr. Calculate the drug diffusion coefficient and permeability in the membrane.
(2) If the initial drug concentrations are 10 mg/ml in the donor solution and 0 mg/ml in the receptor solution. The change in the drug concentration in the receptor solution is measured as a function of time, as shown in the table below. Also shown is the drug concentration change when the membrane is treated with a thin layer of coating. Determine the permeability of the membrane with and without coating to the drug.
Time (min) Without coating (mg/ml) With coating (mg/ml)
0 0 0
60 0.45 0.1
300 1.35 0.5
900 2.5 1.3