Sterile Syringe Filters 0.22 µm

Why 0.22 µm is the sterilising rating

Why membrane choice matters for peptides

Adsorption is the practical risk in filtering a dilute peptide solution. Membranes differ substantially in how much solute they bind, and a high-binding membrane can remove a meaningful fraction of a low-concentration sample before it ever reaches the receiving vessel. Polyethersulfone is favoured in protein and peptide work for its low binding and good flow characteristics. Nylon and some cellulose membranes bind more protein and are better suited to different applications.

Where filtration fits a peptide workflow

• Sterilising a reconstituted solution before transfer into a sterile empty vial for storage
• Filtering buffers and diluents prepared in-house before they contact study material
• Preparing cell culture media additions that cannot be autoclaved

Limits worth stating

Filtration sterilises; it does not purify. The filter removes particulate and microorganisms above its rating and nothing else — degraded peptide, dissolved impurities and endotoxin all pass straight through. Filtering also cannot rescue a solution that has already been microbially contaminated, because the metabolic products and endotoxin left behind remain. It is a step for maintaining the quality of an already-sound preparation, not a corrective measure.

Open the wrapper only at the point of use and keep the connections untouched. Draw the solution into a syringe, attach the filter to the luer-lock inlet, expel headspace air, then push slowly and steadily — high pressure risks deforming the membrane or dislodging the housing seal. Discard the first few drops if hold-up volume matters to your quantitation, and remember that a 25 mm device retains a small dead volume, which is significant when the total sample is only a millilitre or two. If flow becomes hard, stop and use a second filter rather than forcing it: resistance means the membrane is loading. Use each filter once, then dispose of it; never autoclave, rinse or reuse.