Sterile filters

Sterile filters can be used in a forward (syringe>filter>tube) and backward (tube>filter>syringe) direction to remove microorganisms and particles depending on the chosen pore size. Commonly used filters include Millipore's single use Millex filters.

Pore size

 * 0.10 µm - 100 nm
 * 0.22 µm - 220 nm
 * 0.45 µm - 450 nm

Size comparison

 * 0.01-0.3 µm - 10-300 nm viruses
 * 0.4-0.6 µm - 400-600 nm Lactobacillus brevi/Listeria innocua width
 * 0.7-1.2 µm - 700-1200 nm E. coli width
 * 4 - 6 µm - 4000-6000 nm S. cerevisiae diameter )

Comments
In my hands, I lose about 0.4ml in a 33mm Millex 0.22µm filter. If I squeeze through 5ml of water, the initial volume recovered is about 4.5ml. With three air washed, I can recover 4.6ml in total 0.4ml remains stuck in the filter (dead volume). --JS 06:35, 25 February 2009 (EST)

Links

 * Millex® 33 mm Filter Units with Durapore® PVDF Membrane - description and test
 * Effect of pore size on microbrial recovery - Millipore