Pipetting Best Practices
Pipetting accuracy is typically NOT decided by the brand of pipette you purchase. In fact, many of today’s pipettes are designed with the quality to perform to similar tolerances. Measurement accuracy is actually based more on the skills and techniques of the pipette user, their choice of pipette and pipette tip for their application. Training your team on recognized pipetting best practices is often a better investment than new equipment.
The reality is that the vast majority of pipette accuracy is determined by the user’s skill level. Failing to follow pipette best practices is the most often overlooked source of pipette error. This is why a skilled scientific hand and a thorough understanding of technique will always produce more accurate pipette measurements. Alternatively, unskilled pipette users are inconsistent and produce weak results.
Here are some of our best practices for maximizing pipette accuracy.
Best Practices for Pipetting Accuracy
Follow these steps to ensure increased pipette accuracy in any laboratory setting:
- Proper Pipetting Angles – Angles play a critical role in both maximizing pipette performance and minimizing user errors. Aspirating at a vertical 90° angle but dispensing at a 45° angle with the tip touching the side of the receptacle helps deliver the most accuracy at each measurement.
- Pre-wetting — After installing a tip onto your pipette, aspirate the select volume of liquid and dispense it back into the source container. This is pre-wetting and it helps achieve pipetting accuracy by allowing the second aspiration – the liquid you actually transfer to the receptacle – to be completely dispensed from the tip.
- Aspiration Depth — During each aspiration step, it is critical to submerge your pipette tip no more than 1-2mm below the surface of the liquid to avoid adhesion of the liquid to the outside of the tip.
- Consistent Smooth Speed and Pressure — While aspirating and dispensing liquid, use a smooth controlled speed through to the first stop and through to the blowout. Never let a plunger ‘snap’ up or ‘squirt’ the liquid from above the receptacle.
- Touching off — When dispensing liquid from the pipette tip, it is critical to “touch off,” or dispense the liquid against the side of the receptacle. This helps pull the entire measured volume out of the tip.
- Blowing out — As you dispense a liquid against the side of the receptacle, always depress the plunger past the first stop, all the way to the blowout.
- Change Tips — Pipettes and pipette tips are designed to work in harmony as part of a pipetting system for delivering liquids with accuracy and precision. Tips are designed for single use. Re-using a tip for multiple transfers may cause accuracy to vary from one measurement to the next.
- Manage Temperature Transfer — Pipettes are very susceptible to thermal transfer from your hands. This warmth significantly affects the accuracy and precision of the instrument over time. For pipettes, the best practice is to hold the instrument only when you are using it. Place the pipette in its holder in between uses, after you eject the tip.
- Equilibrate Pipette Temperatures — Pipettes are part of a pipetting system. The system includes the user, the pipette, the tip, the liquid and the receptacle. Ideally, pipetting is most accurate when all components of the system are at the same temperature. This is not always possible with liquids (reagents/buffers), but for test labs, it is critical.
- Protect Against Contamination — Pipettes are very susceptible to contamination, especially the nozzle and internal piston chamber. The ‘best practice’ for preventing pipette contamination involves both caution and barriers. Barrier tips (filter tips) are the most common preventative products available, but some pipette models are designed for use with nozzle filters.
- Clean Pipette Exteriors — Minimize pipette contamination and cross-contamination by wiping down the pipette each day, especially the tip end.
- Store Pipettes Vertically — Storing pipettes vertically minimizes pipette contamination, sample cross-contamination and damage. Using a pipette stand, carousel or shelf mount also makes it easy to put down a pipette for fatigue breaks.
Knowing your Pipette Will Make You More Accurate
Another important component to improving pipetting accuracy is to know your equipment. This includes:
- Following Manufacturer Directions – Pipettes are sensitive instruments that take a lot of abuse so the manufacturer’s calibration and preventative maintenance schedules should be scrupulously followed. Regular maintenance and calibration are essential to ensuring pipette accuracy. There are many places within a laboratory to save money, but skimping on regular calibration and maintenance should not be one of them (“an ounce of prevention is worth a pound of cure”).
- Knowing how to use your specific device – Although many pipettes look or function similarly, there is a range of unique designs, different functionalities, and special features. Reviewing the user’s manual, or seeing a demo of your pipettes in action will provide you with opportunities to discover how particular products perform, feel, and work with your preferred pipette tips, and familiarize yourself with pipetting best practices for your particular instrument.
- Viewing Pipette Accuracy Tutorials and Training – Regular pipette training for all users is an easy and effective way to establish, maintain and improve measurement performance in the lab. That’s a big reason why Transcat provides comprehensive pipette accuracy training programs with a variety of easy-to-access training options. We have also produced a series of comprehensive and short, instructional training videos.
Transcat offers online and in-person training in the best practices for pipetting accuracy. Contact our office today for more information.
