A NOVEL AUTOMATED-METHOD FOR THE DETERMINATION OF MEMBRANE-PERMEABILITY IN GAS-LIQUID TRANSFER APPLICATIONS

A novel automated test method for determining the gas transmission rat es of sheet membranes is described. The experimental conditions are re levant to applications involving a hydrophobic membrane barrier separa ting a liquid phase and a gas phase, such as an oxygenator for use in heart-lung bypass, Steady state transfer is accomplished by passing th e test gas under isobaric conditions through the membrane into a recir culating reaction solution. The gas transfer rate is given by the time d volumetric displacement of the test gas which is los ed by a microco mputer. The microcomputer also implements a controller which maintains constant (atmospheric) gas pressure. Oxygen and carbon dioxide permea bilities of microporous flat sheet polypropylene (Celgard(R) 2400 and 2500 series, Hoechst Celanese Corp.) and polydimethylsiloxane (Scimed Life Systems Inc.) membranes were evaluated using this method. As expe cted, the transfer rate of the homogeneous membrane was found to be lo wer than that of the microporous membranes, while the results for micr oporous membranes point towards the importance of liquid ''plugs'' in the pores in influencing permeability. The method was found to give ra pid and reproducible results, and automation facilitated the transfer of data for analysis.