1.3: Micropipetting - Biology LibreTexts

Part I: Choosing and Setting the Micropipette

There are several sizes of micropipettes used in the biotechnology lab. Today, you will be using the P-1000, P-200, and P-20. The P-1000 measures volumes between 100-1000 µl, the P-200 measures volumes between 20-200 µl, and the P-20 measures volumes in the 2-20 µl range. It is important to always pick the correct micropipette for the volume to be measured.

Looking at Figure 3.1, you can see that each micropipette has a similar but different display window. For the P1000, the red number indicates the thousands place, followed by the hundreds, tens, and the ones displayed as small vertical lines. Each line represents 2 µl. The P-200 is reads differently. The display from the top down reads, hundreds, tens, ones, and the vertical lines are considered 0.2 µl. Finally, the P-20 can be read from the top down tens, ones, and the red tenths.

A. Choosing your Micropipette

For each amount listed below, indicate the correct micropipette needed to measure the volume accurately then set the pipette to the indicated amount and show your partner.

Table 1. Pipette Size Choice

Amount	Pipette Needed		Partner Observation
567 µl:
2. 160 µl:
3. 700 µl:
4. 25 µl:
5. 15 µl:

B. Setting your Micropipette

Materials

• P-20 micropipette
• P-20 tips
• Waste container
• Tube of red dye in tube rack
• Laminated sheet for pipetting

Procedure

1. Each student will load 5, 10, 15, and 20 µl of red dye onto the laminated sheet.
2. Locate the p-20 and set the dial to 5 µl.
3. Hold the micropipette in your dominant hand, and gently but securely place the end of the micropipette into the proper size tip. Once the tip is on, be careful not to touch the tip on anything! If your tip touches the bench, lab coat etc. eject the tip into the waste container and get a new clean pipet tip.
4. With your other hand, open the cap of the tube of red dye and bring the tube of red dye to eye level,
5. Push the micropipette plunger down to the first stop and hold your thumb in this position.
6. Place the pipet tip into the red dye solution.
7. Gently release your thumb from the plunger to draw fluid into the tip.
8. Confirm that the tip has liquid and that no bubbles are present within the tip.
9. Close the tube of red dye and place back in tube rack.
10. Gently touch the tip to the center of the circle labeled 5 µL and slowly push all the way down (to second stop) on the plunger to dispense the liquid.
11. Repeat this process for the remaining volumes.
12. Be sure to watch your groupmates to provide feedback and help with their technique.

Results

Take a picture or draw a picture of your spots and include this in your lab notebook as Figure 1. Make sure the figure has a title.

Conclusion

1. Observe if your spots were similar in size to your groupmates.
2. Which volume had the most variability?
3. What could have contributed to your spot being too large or small?