Bubble point test

Determining if a sterilizing grade filter is integral can be done via non-destructive integrity testing.

The basis for the integrity testing of filters depends upon the interpretation of airflows through membranes wetted by water or other fluids. The bubble point measurement identifies the largest (diameter) pores present in a membrane by the differential pressure required to empty them of their water. The largest (diameter) pores are vacated first. The pores thus sized are correlated with their ability to restrain the passage of organisms. It is this correlation that enables a filter to be characterized and selected for an application requiring a given pore retention value.

The differential pressure supplies the work function necessary to disrupt the bonding between the water molecules and the molecules of the hydrophilic pore surface that constitutes wetting, and to forcibly separate the water from the pore walls. The bonding strength of the wetting interaction to be overcome is peculiar to each filter/fluid combination.

The utility of the bubble point derives from its identifying a filter’s largest pores as measured by the differential pressure required to expel the water from a wetted filter

For more information visit www.hallpyke.ie/products/integrity-testing-services/