There's long been a lively online debate about the merits of reusing pipette tips ,versus sending them to landfills. This is despite the fact that for at least two decadesIS0 8655-2 (governing "Piston-operated volumetric apparatus-Piston pipettes") hasstipulated:
"Pipette tips made ofplastic forpiston pipettes with airinterface are designed forsingle use. They shall not be cleaned forreuse.
Pipette tip reuse came to the fore during the pandemic. At that time supply chainissues left many labs without tips, while COVlD PCR tests (a public health linchpin)were requiring several tips per test.
The pipette supply chain seems to be fine now, and home COVlD tests are in amplesupply. But it's not irrational to ask if there is an alternative to single-use pipette tips.In 2021, the University of California, Santa Barbara (UcSB) noted that pipette tips andboxes were among the leading contributors to laboratory waste. According to UCSB,pipette tip boxes alone accounted for 80 percent of the plastic lab waste at MiT. lt wasaround this time that we first dove into the topic, with a brief blog on quickly rackingtips for sterilization and reuse.
Q: ls it OK to Reuse Pipette Tips? A: lt's Complicated!
Most discussions of pipette tip reuse focus on the possibility of cross-contamination-which is a valid concern, But a quick dip into lS0 8655-2 reveals that the real issue ismore fundamental:
Micro-pipetting is all about precision and accuracy, and most plastic tips will notremain reliably accurate with multiple uses. According to the original (2002) 1s0 86552, reuse of pipette tips can lead to up to 4.0 percent error, far exceeding maximumpermissible error for this equipment.
That said, lS0 8655-2 has always differentiated between air-displacement andpositive-displacement pipette tips. This is, in fact, the source of some controversy.
Air-displacement pipettes are the ones most familiar to most lab workers. In thisapparatus, there's an air buffer between the piston and the liquid being pipetted.Assuch, the disposable plastic pipette tip is the only part of the device that comes intocontact with the sample. This minimizes avenues for contamination. But it also makesprecision and accuracy more challenging, especially with viscous or dense fluids, orunder some ambient temperature and atmospheric conditions. Air-displacementpipettes work best with aqueous and non-viscous liquids.
Positive-displacement pipettes are somewhat less common, and designed verydifferently. Here the tip is a multi-part affair, with a sliding "capillary" (plunger) thatgoes all the way down the tip and can directly contact the fluid. This lends itself torepeatable precision, even with "problem liquids" (e.g., those that are dense,viscous, volatile, hot, cold, or foaming). But this design also increases costs and addsavenues of cross-contamination.
According to 1S0 8655-2, positive-displacement pipette tips may be disposable orreusable. But the simpler plastic air-displacement pipette tips are not reusable.
Should Our Lab Be Reusing Pipette Tips?
In most labs, air-displacement pipettes with disposable tips are likely the norm. Thecombination of reduced risk of contamination, convenience, and lower cost is just tooattractive. That being the case, ls0 8655-2 is unambiguous: You should use each tiponce and then dispose ofit.
However, many labs are making their own determination, based on the sensitivity oftheir work to contamination. Labs must also take into account the metrological issuesthat come with reusing disposable plastic air-displacement pipette tips betweensamples, let alone after autoclaving.
Uncomfortable with the mountain of plastic waste, yet unable to consider reusingplastic tips or shifting to positive-displacement pipettes with reusable tips?Zhejiang Biorear Biotechnology bio-based pipette tips might be worth a look.