Filtration for sample and media prep. Globe Scientific syringe filters come in PES, nylon, PTFE (standard and hydrophobic), hydrophobic PVDF, MCE, cellulose acetate and CA with a glass-fibre prefilter, at 0.10, 0.22 and 0.45 µm in 13 mm and 30 mm diameters. There are also sterile PES bottle-top filters and complete vacuum filter systems for 150 to 1000 mL. The pumps that drive them are an oil-free scroll pump, the Aether 8 Eco rotary vane pump and the Welch 2052 chemical-resistant diaphragm pump.
How to choose
0.22 µm or 0.45 µm?
0.22 µm is the sterilizing grade, used to remove bacteria when filter-sterilizing media, buffers and additives that cannot be autoclaved. 0.45 µm clarifies: it takes out particulates before HPLC or analysis, and it flows faster, but the filtrate is not sterile. 0.10 µm is used where mycoplasma is the concern.
Which membrane should I choose?
PES has low protein binding and fast flow, and is the standard for cell-culture media. Cellulose acetate binds even less protein. Nylon handles most organic solvents and aqueous samples for HPLC prep, but it binds protein. Hydrophobic PTFE is for aggressive solvents and for venting gases. A glass-fibre prefilter over CA keeps heavily loaded samples from clogging the membrane.
Bottle-top filter or a complete system?
A bottle-top filter screws onto your own storage bottle and filters straight into it, so the filtrate never changes containers. A complete vacuum filter system comes with its own receiver bottle, which is simpler when you do not have a sterile bottle ready to use.
Oil-sealed or oil-free pump?
Filtration needs only a modest vacuum, so an oil-free diaphragm or scroll pump does the job without oil changes. The Welch 2052's chemical-resistant heads also stand up to solvent vapour. An oil-sealed rotary vane pump like the Aether 8 reaches far deeper vacuum (0.003 mbar). That depth is for freeze drying, degassing and vacuum ovens, and it needs a cold trap and regular oil changes.
