There’s no question that pipettes are among the most important tools for biological research. They come in a variety of designs and are used in a myriad of research areas. While many liquid-handling guidelines emphasize the importance of pipette maintenance, developing pipette technique is just as crucial. Below, we share some tips, from pipette vendors and power users, for improving your pipetting technique.
1. Choose the right pipette and tip: There are many options to pick from, and this decision can have widespread repercussions. Mismatching the tip and pipette, or using poor quality tips, could compromise the seal between the tip and the pipette. Good quality tips ensure an appropriate seal thus minimizing sample loss due to leakage.
2. Calibrate and pipette based on liquid density: Recalibrate your pipette if the liquid has a considerably different density than water. If you’re pipetting viscous liquids, make sure to do it at a slower speed and work in reverse pipette mode. When pipetting volatile liquids, do it quickly and use the reverse pipette mode.
3. Pre-wet the tip: To reduce variations in volume delivery, pre-wet your tip at least three times. By doing so, you can help create a temperature equilibrium and bring humidity into the dry space inside the tip. Skipping this step could compromise the accuracy of the volume dispensed due to evaporation. If you skip the pre-wetting procedure, the first few dispenses tend to deliver less volume.
4. Aspirate correctly: Immerse the tip just below the liquid’s surface. Make sure to discard the first aspiration. When aspirating, the tip should not be too deep below the meniscus, as immersing it too much could cause you to aspirate excess volume. At the same time, keeping it above the liquid could cause you to aspirate air, creating inconsistencies in the volumes of your samples.
5. Pause after each aspiration: Slow, even, plunge releases help minimize errors. After releasing the plunger with the tip in the sample, it's a good practice to pause. This can be especially important when handling viscous liquids. Try, whenever possible, to make consistent one to two second pauses after each aspiration, which allows the liquid to stabilize inside the tip.
6. Keep the pipette angle consistent: Hold the pipette at a consistent angle not exceeding 20 degrees. When pulling the pipette, make sure to do it vertically and to not touch the tip on the side of the container. This can be especially important when handling small samples. After aspirating, pull straight out.
7. Be slow and consistent: Use consistent and steady speed and pressure when handling the pipette and samples. When you’re paying attention to detail and steady movement, you are ensuring reproducibility and minimizing volume errors. Inconsistency in speed or pressure within the technique allows for error to creep into workflows in ways you might not expect.
8. Look out for temperature: If your experiment allows, make sure the pipette, tips, and liquids are all at room temperature. Changes in temperature can lead to contraction or expansion of the air inside the pipette tip, which could potentially impact the accuracy of the liquid dispensed. Also, when possible, avoid over handling the pipette and tip as your body heat could impact the volume of liquid dispensed. As a good rule of thumb, hold the pipette lightly and place it on the stand between uses.
9. Do your best to preserve pipetting performance: Because pipetting is all about consistent performance and scientists typically aspirate and dispense liquids thousands of times a month, taking care of your pipette is crucial. In this article, we discussed tips that can help extend the life of your pipette. Overall, we recommend that you clean your pipette on a weekly or monthly schedule, keep an eye out for leaks, and make sure to keep it calibrated.
10. Prevent injury by paying attention to the ergonomics of pipetting: Proper technique is essential not only to ensure accurate pipetting but also to avoid injury. Previously, Biocompare sat down with power pipettors to discuss the ergonomics of pipetting. In this article, you will find tips on how to prevent injury from frequent pipetting. In summary, tips included paying attention to your posture, using the right material and pipettes for your work, checking in to make sure you’re following an appropriate pipetting form, and keeping your work area organized.
Regardless of the application, pipetting competency is essential for ensuring overall research quality. Through mindfulness of your technique, you can help build reproducibility within your data as well as extend the life of your pipette.