# Pipette Accuracy Activity

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.

 Materials – Distilled water – Food coloring -Heavy absorbent paper such as watercolor paper, filter paper, or paper towel Equipment/Labware – Micropipettes – Pipet tips – Scientific scale – Wax paper or weigh boats

Pure water weighs 1 gram per milliliter, which makes it very easy to test your pipetting skills. If you pipet 1000 Î¼l onto the scale, it should weigh 1 gram or 1000 Î¼g. Micropipettes usually come in four sizes: 2 Î¼l, 20 Î¼l, 200 Î¼l, and 1000 Î¼l. 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

1. 15 Î¼l
2. 100 Î¼l
3. 750 Î¼l
4. 1400 Î¼l

Answers: 1) use the 20 Î¼l, 2) 200 Î¼l, 3) 1000 Î¼l, 4) there are a few different ways, 1000 Î¼l + 200 Î¼l + 200 Î¼l; 1000 Î¼l + 400 Î¼l , or use the 1000 Î¼l to measure out 700 Î¼l, twice. If measuring out a volume over 1000 Î¼l, it’s easier to divide the volume in half and measure the same amount out twice instead of re-setting the pipet.

Pipetting Activity

1. 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.
2. Pipet the volumes in the Table using the micropipette indicated and record the weight of the water drop.
3. 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 Ã Volume â†“ 20 Î¼l 200 Î¼l 1000 Î¼l 17 Î¼l 100 Î¼l 192 Î¼l 847 Î¼l Use all three sizes to measure out 1222 Î¼l 1222 Î¼l Use just the 1000 Î¼l to measure out 1222 Î¼l 1222 Î¼l Try a few more variations and write down your results. Be sure to make a note of which pippetors you used.

Pipetting activity 2:

1. Put a few drops of food coloring in different containers of water
2. Using the 20 Î¼l pippetor, pipet drops of colored water onto thick paper
3. Practice keeping droplets of the same volume the same size on paper
4. “Draw’ patterns in different colors and different volumes