How to Reduce Pipetting Errors

Pipetting is one of the most frequent procedures in most life sciences labs. However, not everyone learns good techniques when they start working in labs.

Fortunately, it's never too late to improve or brush up your skills. Here's how to reduce pipetting errors so you can ensure accuracy in the lab.

Perform Proper Pipettor Maintenance and Technique

Regular pipettor maintenance and proper pipetting technique are important for achieving the high pipette accuracy (agreement between intended and true volume) and precision (consistency between one volume dispensed and the next) you need for valid and successful experiments.

Possible consequences of poor maintenance and pipetting technique can include excessive wear and tear on pipettors, sample contamination, and dispensing wrong or inconsistent volumes across an experiment. In turn, these problems could lead to further issues like wells drying out, incorrect dosing of compounds, or inconsistent cell growth, impacting your experiment results.

Long-Term Pipettor Maintenance

Following regular maintenance procedures is important because a lack of maintenance can lead to "silent" failure you may not be able to detect. Perform proper maintenance and calibration on all your lab's pipettors at least once a year, or as recommended by the manufacturer. Replace any worn parts at that point.

Pipettors used for very small liquid volumes should be calibrated more often, usually every three months. Many labs contract with professionals for scheduled calibration, while others learn to properly calibrate their pipettors in-house.

Liquid Handling Ebook: A Guide to Pipetting Success

Good Pipetting Practices

Daily Pipettor Maintenance

Clean pipettors daily by giving them a quick wipe-down with 70 percent ethanol. Give your pipettor a deeper clean about every three months or before performing procedures sensitive to contamination. Refer to the manual to learn how to dismantle, clean, and reassemble your pipettor.

If you need to sterilize or decontaminate your pipettor, look up the proper way to do this depending on the circumstances. Some pipettors can be autoclaved.

Pipetting Technique During Experiments

These tips can help you reduce pipetting errors during experiments:

  • Push down to attach the tip securely, but don't push so hard that you bend or warp the tip.
  • Pre-wet the pipet tip by taking up some liquid and releasing it.
  • Don't rush. Always push down and let up the plunger slowly. If you aspirate too fast, you may draw in an air bubble, or you may aspirate liquid into the pipettor body. Dispensing too fast can create aerosols or splashes. It can also damage the cells you're handling.
  • According to an article in Bioinformation, an improper immersion depth or angle can decrease pipetting accuracy. Keep the pipettor in a vertical position while aspirating liquid, but hold it at a 30- to 45-degree angle while dispensing liquid. Never tilt the pipettor so far that liquid could run into its body. Look up the correct immersion depth for the volume you're pipetting, and use this depth consistently.
  • After lifting the plunger, pause briefly with the tip under the surface to allow liquid to finish filling the tip. Since evaporation will also occur from the liquid surface inside the tip, try to keep this pause as consistent as possible from sample to sample.

It's also important to prevent fluctuating environmental conditions in the lab. Variations in laboratory environmental conditions like temperature, relative humidity, and barometric pressure can cause changes in pipetting accuracy from day to day.

Forward and Reverse Pipetting

Forward pipetting is the most common pipetting technique, and it should be used for most aqueous solutions. To forward pipet, push the plunger down to the first stop, no further. At the correct immersion depth, slowly draw in liquid. Then dispense the liquid, pushing the plunger down to the second stop to get all of the liquid out of the tip.

Reverse pipetting is an alternative technique that provides a volume cushion, and it can help when you're pipetting viscous, volatile, or foaming liquids or handling very small volumes. To reverse pipet, push the plunger down to the second stop. Then immerse the tip and slowly release the plunger to draw in liquid. To dispense, push the plunger to the first stop only. Discard the excess liquid left in the tip, or return it to its container.

Choose the Right Pipettor and Store It Correctly

In addition to recognizing improper pipettor maintenance and technique, understanding other common mistakes can help you learn how to reduce pipetting errors. These mistakes include choosing the wrong pipettor size and tip for the volume you're handling and storing pipettors incorrectly.

Pipettor Size

Pipettors come in different sizes, typically ranging from 0.1 μl to 1000 μl or more. Use the smallest pipettor that can handle the volume you want to dispense — accuracy and precision decrease near the bottom of each pipettor's volume range. For instance, instead of using a 10-100 μl pipettor to dispense 10 μl of liquid, choose a 0.5-10 μl pipettor.

Dispensing tiny volumes with accuracy and precision is difficult. Consider diluting your sample so you can pipette a larger volume of liquid but arrive at the same concentration in the final mixture.

Pipettor Tip

Choose a tip whose material and shape are suited to the substance you're handling and its viscosity. If you're using corrosive samples that evaporate, use a filtered tip to protect the pipettor. Filtered tips can also be useful for preventing cross-contamination between samples.

Pipettor Storage

When not in use, store pipettors properly on a stand that keeps them upright.

Finding Pipettors, Pipet Tips, and Resources

Corning offers a wide array of pipettors and tips, plus guides and resources to help you improve your liquid handling techniques and choose the right products. Explore the Corning catalog to find the pipettors you need today.