A novel automated method for the determination of membrane permeability in gas-liquid transfer applications

Abstract

A novel automated test method for determining the gas transmission rates of sheet membranes is described. The experimental conditions are relevant to applications involving a hydrophobic membrane barrier separating a liquid phase and a gas phase, such as an oxygenator for use in heart-lung bypass. Steady state transfer is accomplished by passing the test gas tnder isobaric condition tthrough the membrane into a recirculating reaction solution. The gas transfer rate is given by the timed volumetric displacement of the test gas which is logged by a microcomputer. The microcomputer also implements a controller which maintains constant (atmospheric) gas pressure. Oxygen and carbon dioxide permeabilities of microporous flat sheet polypropylene (Celgard ® 2400 and 2500 series, Hoechst Celanese Corp.) and polydimethylsiloxane (Scimed Life Systems Inc.) membranes were evaluated using this method. As expected, the transfer rate of the homogeneous membrane was found to be lower than that of the microporous membranes, while the results for microporous membranes point towards the importance of liquid “plugs” in the pores in influencing permeability. The method was found to give rapid and reproducible results, and automation facilitated the transfer of data for analysis.