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Filtration

Filtration removes particles, cells or microorganisms from a liquid. The membrane material and pore size decide what gets through and what sticks to the filter along the way.

Pore size by purpose

Larger pores clarify a solution by removing debris. Smaller pores are used when the aim is to remove bacteria as well, which is why sterilising filtration relies on the finest membranes in common use.


Membrane chemistry matters

Different membrane materials bind different amounts of protein and tolerate different solvents. A membrane that works for aqueous buffers may dissolve or bind the sample in other conditions — check compatibility before filtering anything valuable.


Formats

Syringe filters handle small volumes, vacuum units handle larger ones, and spin columns use a centrifuge to push liquid through a membrane or resin — the format behind many extraction kits.

More pages

  1. PCR and RT-PCR: how amplification works and fails
  2. Gel electrophoresis: separating DNA and proteins by size
  3. Why this site exists