Prefilters reduce filtering time and replacement of primary filters by trapping large particles before they reach the final membrane. For use in this way, a prefilter of slightly smaller diameter than the final filter is recommended so that the prefilter fits inside the O-ring or filter funnel for a positive seal.
Prefilters can also be used as the main filtration medium where complete retention of contaminants above the nominal pore size is not critical.
Borosilicate glass fibers woven into a porous matrix and bonded by an acrylic resin. PreSep™ prefilters are biologically inert, autoclavable, and resistant to oxidizing agents and weak acids. Not recommended for use above 125°C or with solvents capable of extracting the binder.
Type G15 prefilters have nominal pore size rating of 0.50µm with excellent retention efficiency but limited dirt-handling capability. Use for upstream protection of 0.20 to 0.80µm membranes.
Type G20 prefilters have nominal pore size of 1.0µm, giving greater dirt-holding capacity but with lower retention efficiency than the type G15 filters. Used upstream of G15 in serial filtration stacks.
Type G25 prefilters have approximately the same retention as G20, but because of their greater depth, they have better throughput and dirt-holding capacity. Useful for filtering protein-containing solutions and liquids with heavy contaminant loads. Use upstream of G15 in serial stacks.