Technique: tips for pipetting

Precise pipetting is essential to all experiments, and it ensures that the data is precise.

For example, for loading SDS PAGE gel to examine how well you conducted your protein isolation, it is important there equal amounts of protein are loaded in order to examine the bands correctly. If one well has more sample than the others, then it will provide inconsistent, incorrect data.

Image was obtained from Kind Saud University, http://faculty.ksu.edu.sa/moncef/Pages/OperatingtheMicropipette.aspx (accessed date 4/14/2011).

When pipetting:

1. Choose a pipette that has the maximum volume closet to the desired volume that you want to pipette out. 

The 100 ul pipette should be used to pipette out 50 ul of Rubisco, because the maximum capacity of the pipette is closer to the desired amount of 50 ul. There is more precision with the 100 ul than there is with the 1000 ul pipette.

2. Set the correct volume on the pipette.
3. Hold the pipette vertical, the whole time when pipetting, so that no solution will enter the barrel and ruin the pipette.  
FYI = (A pipette costs ~ $400)  
http://www.eppendorfna.com/int/index.php?l=131&action=products&catalognode=9477&productpage=4
4. Slowly draw up the solution into the pipette.
5. When pipetting out a solution, press down until you feel the first stop, then when you want to release the solution, press all of the way down to the second stop. If you don't do this, then your volume isn't accurate, you may be pipetting too little or too much of the solution.


More tips:
- Pre-wet the pipette tip with the desired solution, before actually pipetting it out. By doing this, there won't be any solution stuck in the pipette tip, and it will ensure that an accurate volume was dispensed.
Oswald, N. 17 Ways to Stop Pipetting Errors Ruining Your Experiments. http://bitesizebio.com/articles/17-ways-to-stop-pipetting-errors-ruining-your-experiments/ (accessed date 4/14/2011).
- Store pipettes vertically to prevent any solutions from entering the barrel.
- After using the pipette return the pipette to its maximum volume to prevent messing with the calibration. For example, you are using a 100 ul pipette, and you want to pipette 50 ul, after pipetting that amount change the pipette volume back to 100 ul.

- If you are uncertain about how well you pipette, measure that volume on a balance (1 milliliter = 1 gram, then 1,000 ul = 1 gram).

To see how accurate your pipetting is measure the solution on a balance. Since 1,000 ul = 1 mL, then it equal 1.00 gram on the balance, because 1 mL = 1 gram.