Techonology of syringe filter

•Filter Integrity

       The results from integrity tests are used to determine the ability of  syringe filters to perform as they are intended. Filter integrity was tested by forcing an aerosol of sodium chloride solution (0.9%) through the filter and counting the particles downstream of the membrane. This test method has  been correlated to the HIMA bacterial challenge test.

 •Flow Rate

        The purpose of this test is to determine if the assembled filter device meets the minimum specified water flow rate. Water is passed through the device at a specified pressure and collected in a graduate  cylinder for 60 seconds.

•Hold-up Volume 

        The purpose of this test is to evaluate the amount of water remaining in the unit after performing an air flush at a pressure below the bubble point (dead volume) and after the bubble point test (hold-up volume). Acceptance criterion is less than or equal to 0.08 ml or 80 μl hold-up volume.

•Housing Burst Test 

        The purpose of this test is to determine the integrity of the housing and the maximal level of  resistance to pressure. The syringe filter units are mounted to a manifold and the downstream fittings are plugged. The units are pressurized with air until they burst. An acceptable device meets or exceeds the minimum burst pressure specification.

•Water Bubble Point

         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.

•Housing Integrity Test

          The purpose of this test is to confirm proper overmolding, the process of molding the colored ring  on the device perimeter, which simultaneously seals the housing top and base together, and seals the membrane within the device. The outlet fittings of the test samples are plugged, and units are submerged in a tank of water and pressurized with air at the inlet fitting, to the pressure. The acceptance criterion is no leak or visible bubbles during one minute at  the pressure.