Filtered and Low-Binding Pipette Tips: How to Choose

Pipette tips look interchangeable and mostly are, right up to the moment a filter is needed, a low-copy sample is lost to the wall of a tube, or a tip fails to seal on the shaft. The four variants BUNSEN supplies — standard, filtered, low-binding, and filtered low-binding — exist because those three failures have different causes. This page sets out what each one does, so the choice comes down to the sample rather than the price list.

What the four tip types actually do

Type	What it adds	Typical use
Standard	Nothing beyond the moulded tip and rack	General reagent transfer, diluent make-up, non-critical work
Filtered	A hydrophobic barrier between sample and pipette shaft	PCR and qPCR set-up, cell culture, infectious or hazardous samples
Low-binding	A hydrophobic inner surface that resists protein and nucleic acid adhesion	Enzymes, antibodies, DNA/RNA, low-copy templates, expensive reagents
Filtered low-binding	Both of the above	Low-copy nucleic acid work where contamination and loss both matter

Filter tips: what the barrier is and is not

A filter tip carries a sintered plug of hydrophobic ultra-high molecular weight polyethylene (UHMWPE) seated above the liquid column. Aerosols and droplets travelling up the shaft hit the plug and stop; air still passes, so aspiration and dispensing feel unchanged. The plug has a uniform pore structure, which is what separates a working barrier from a decorative one — an uneven matrix leaks at the thin points.

What the barrier does not do is make a non-sterile tip sterile. Filtering is about carrying contamination one way, from the sample into the pipette. Sterility is a separate claim, and both are separate again from DNase/RNase-free and pyrogen-free certification.

When a filter tip is not optional

• Any PCR or qPCR set-up. Amplification products from the previous reaction are the classic source of false positives, and they travel on aerosols.
• Cell culture and sterile media handling, where a contaminated shaft ruins a flask rather than a tube.
• Volatile, infectious or radioactive samples, where the concern is the operator and the pipette, not only the sample.
• Shared instruments and multi-user benches, where the shaft itself is the weak link.

Low-binding tips: where the sample actually goes

In an untreated polypropylene tip, a fraction of a protein or nucleic acid solution stays on the inner wall after dispensing. The loss is invisible and, at 10 µL, it is a meaningful share of the volume — which is why low-copy work and enzyme master mixes are the two places people notice it.

BUNSEN low-binding tips are surface treated so that residue is held to within about 0.5 per cent of the dispensed volume, a reduction of more than 90 per cent against conventional tips, with little measurable adhesion of DNA, RNA or protein to the wall. The treatment is on the inside only; the outside stays grippy enough for rack handling.

Application	Why low-binding helps
Restriction digests, ligations, polymerase mixes	Enzyme sticks to untreated walls; the next tube receives less than intended
Low-copy template and standard curves	Wall loss shifts the low end of the curve, which is exactly where it matters
Antibody and protein standards	Protein adsorbs strongly to plain PP; concentrations drift downward over a series
Costly reagents	Recovering the last microlitres from a high-value vial is a direct saving

Fit and sealing: the part buyers underestimate

A tip that does not seal leaks air, and a tip that seals too hard is worse: it fails to eject cleanly, then the user compensates by forcing it and the shaft takes the load. Two fit families cover most of the market — a universal taper that suits a wide range of shafts, and a light-touch style with a longer, narrower seal for low-force ejection.

Two things decide whether a batch works on your instrument: the depth at which the tip seats, and the force needed to eject it. Both are measurable in less than a minute.

A 30-second seal check before you commit to a batch

1. Fit a tip, aspirate 200 µL of water, hold it vertically for 30 seconds. No meniscus drop means the seal holds.
2. Dispense and watch for a residual film or a hanging droplet. A droplet means the surface is rejecting the liquid — acceptable for low-binding tips, a warning sign for standard ones.
3. Eject. The tip should release with a single clean motion and no shaft flex.

Sterility, certification and packaging

Check what the certificate actually covers, because the four claims are separate: sterile, DNase/RNase-free, pyrogen-free (endotoxin), and cytotoxicity. For cell work, ask for all four. For PCR, DNase/RNase-free plus sterile is the practical minimum.

• Sterilisation method: gamma irradiation leaves no ethylene oxide residue and needs no secondary handling; autoclaved tips in a rack are only as sterile as the rack.
• Rack and refill format: refills cut plastic waste but only stay clean if the rack is washed and dried between fills; a wet rack contaminates the next stack.
• Packaging: individually wrapped or rack-sealed is worth the premium only where the work is genuinely contamination-sensitive.

Selection checklist

Question	If yes
Is the downstream step amplification?	Filtered, plus DNase/RNase-free certified
Is the sample enzyme, antibody or nucleic acid at low concentration?	Low-binding
Is the sample infectious, volatile or hazardous?	Filtered, and consider a barrier tip with a tighter plug
Is the tip used on more than one pipette model?	Universal taper; test seal and ejection force on each model
Does the protocol specify a volume below 20 µL?	Check the tip’s stated minimum volume, not its maximum

Common mistakes

• Buying filter tips for sterility. Filtration stops aerosols; it does not sterilise. Buy both attributes if both are needed.
• Using low-binding tips for everything. They cost more and, in some viscous reagents, hold a larger hanging drop than a standard tip.
• Judging fit by brand name. Fit is about geometry. Test the batch on the instrument that will use it.
• Reusing racks without drying. Residual moisture in a rack is a contamination route that no tip design can fix.

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Note: The information on the scientific research products above is for reference only!