04 April 2015

Improve your pipetting technique

Pipetting: Find proper pipetting technique and eliminate the sources of error in pipetting

Establishing a proper pipetting technique and eliminating potential sources of error in pipetting can be quite a challenge in an everyday lab. When learning how to pipette, a few aspects are worth taking a closer look at.    

First of all, the types of pipetting errors. What are the sources of error in pipetting in terms of accuracy? Accuracy relies in principle on the condition in which your pipette is. How often are you having your pipette serviced? How often should it be serviced? Have you established a protocol specifying that? These are the first questions to address in order to eliminate your pipetting errors in terms of accuracy. 
  
Secondly, how to identify the sources of error in pipetting in terms of precision? It is a common experience that low quality tip can destroy the performance of even the best quality pipette. The tips impact will be reflected in your precision results.
In order to illustrate tips' impact on precision, Capp has made a small test, where we pipetted a colored liquid into a standard tip and ExpellPlus low retention tip. The amount of liquid still remaining in the tip after expelling can be seen on the picture below.

We came to the conclusion that ExpellPlus low retention tips deliver within 0.1% of the sample, vs. 0.7% for standard tips. This is possible thanks to the unique technology of extra polished tip interior, minimizing the liquid retention and improving your results up to 7 times more than with standard tips.   

Thirdly, the user themselves can do much in order to improve their pipetting technique. Inspired by ISO 8655, we have summed up a few tips on how to pipette, eliminating sources of error in pipetting:   
   
1. Use a proper pipette tip (low retention) and make sure it fits the pipette.   
2. Work at room temperature, allowing liquid and equipment to equilibrate.   
3. Examine the tip before sample dispensing and wipe it only if there is liquid on the outside of the tip, being careful to avoid touching tip's orifice.   
4. Pre-wet the pipette tip: Aspirate and expel the sample liquid at least 3 times before aspirating a sample for delivery.   
5. Be consistent in your pipetting technique in terms of plunger pressure and speed.   
6. Immerse the tip between 2 to 5 mm deep during sample aspiration.   
7. Pause for a moment with the tip still in the liquid after aspirating.   
8. Pull the pipette straight out, being careful not to touch the sides of the container.   
9. Do not incline the pipette more than 15 degrees when dispensing.   
10. After dispensing, wipe off the tip onto the container to deliver any of the remaining sample.   
11. Minimize handling of the pipette and tip to avoid transferring of body heat.   
   
We hope above tips will help you to establish proper pipetting technique and eliminate the sources of error in pipetting - both in terms of accuracy and precision. For more information on proper pipetting, write at info@capp.dk. Ask for a free sample of ExpellPlus low retetion tips.

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