1. (4 points) You use a P20 micropipette to transfer 20 1 of water to a microcen
ID: 714838 • Letter: 1
Question
1. (4 points) You use a P20 micropipette to transfer 20 1 of water to a microcentrifuge tube Next you use a P200 to add 20011 of dye to the same tube. Finally, you use a P1000 set to 220 ul to remove the mixture from the tube. You see there is a 2 cm air space at the end of your P1000 pipette tip after all the liquid has been withdrawn from the tube. Propose two specific reasons this could occur and explain how you could test each of these reasons. How will you distinguish between user error (something you did wrong with the micropipette)? wrong) versus instrument error (somethingExplanation / Answer
Answer: 1. While filling the desired micropipette with the fluid, if the pace of aspiration is high, then the air bubble is unable to escape through the liquid. This leads to the production of the air column in the micropipette tip.
2. While aspirating the liquid, if by chance the micropipette tip loses contact with the liquid, some air is drawn in. This may also lead to the creation of an air column.
The difference between user error and instrumental error is that User error is mostly random and can be eliminated by taking a large number of readings. On the other hand, the instrumental error is constant and is eliminated by understanding the mechanism leading to the error.
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