Printable version: calibrate_1.04.v1
Objectives The purpose of this lab is to practice pipetting and test your accuracy. You’ll also gain some experience working with the scientific scale.
Pure water weighs 1 gram per milliliter, which makes it very easy to test your pipetting skills. If you pipet 1000 μl onto the scale, it should weigh 1 gram or 1000 μg. Micropipettes usually come in four sizes: 2 μl, 20 μl, 200 μl, and 1000 μl. Micropipettes generally don’t need to be calibrated (although they should occasionally be serviced by a trained technician), but proper pipetting skills and the correct choice in pipet size can help your accuracy.
Rule of Thumb: choose the pipet that has the maximum volume closest to the volume you want.
Quick Quiz (answers below) What pipette would you use to measure out
- 15 μl
- 100 μl
- 750 μl
- 1400 μl
Answers: 1) use the 20 μl, 2) 200 μl, 3) 1000 μl, 4) there are a few different ways, 1000 μl + 200 μl + 200 μl; 1000 μl + 400 μl , or use the 1000 μl to measure out 700 μl, twice. If measuring out a volume over 1000 μl, it’s easier to divide the volume in half and measure the same amount out twice instead of re-setting the pipet.
- Cover the weigh-pan of the scale with something waterproof such as a piece of parafilm, a piece of plastic, or a plastic weigh-boat. Tare the scale so it reads 0 with the parafilm on it.
- Pipet the volumes in the Table using the micropipette indicated and record the weight of the water drop.
- After each measurement, soak up the water with a paper towel and tare the scale.
Measurement table: Use the different pippetor sizes to measure out the volume in the first column. Record the weight of each drop in the table
|Pipettor sizes àVolume ↓||20 μl||200 μl||1000 μl|
|Use all three sizes to measure out 1222 μl|
|Use just the 1000 μl to measure out 1222 μl|
|Try a few more variations and write down your results. Be sure to make a note of which pippetors you used.|
Pipetting activity 2:
- Put a few drops of food coloring in different containers of water
- Using the 20 μl pippetor, pipet drops of colored water onto thick paper
- Practice keeping droplets of the same volume the same size on paper
- “Draw” patterns in different colors and different volumes