The dialysis of caffeine through selected semi-permeable membranes

Until the past few years, cellulose derivatives, (e.g., cellophane, collodion, and parchment) and animal membranes (e.g., goldbeater’s skin) have been the only dialysis membranes employed commercially. Cellophane has been used as the dialysis membrane in the artificial kidney since the machine’s inception in 1914. It continues to serve in this capacity, even though, in the last few years, attempts have been made to develop better films. An appreciation of both the “solution theory” and the “pore theory” is in order for this discussion. By incorporating the dynamics of these theories in the techniques of membram formulation, improved membrane performance can be exhibited. In the following discussion which considers membrane formulation, improved membrane performance can be displayed by higher particle transfer rates and greater particle selectivity