The syringe filter unit’s bi-directional support of the filter membrane enables users to filter aqueous solutions in either direction (only ONE direction per use):
- forward (from the syringe into the container)
- backward (from the container into the syringe)
The filter unit removes micro organisms, particles, precipitates, and undissolved powders larger than 0.22 micron or 0.45 micron, depending on filter used.
This test consists of measuring the minimum air pressure
required to remove the water retained by surface tension in the largest pores of a fully wetted membrane.
This pressure (the bubble point) is dependent upon the pore diameter and the surface tension of the wetting fluid.
The filter unit is first wet with water, and then the air pressure is slowly increased until a steady stream of bubbles is observed downstream of the filter. This pressure is recorded as the bubble point. The syringe filter must have a bubble point value greater than or equal to 3.7 bar.