Laboratory science often involves working with very small volumes of liquid; frequently millionths of liters are used. One millionth of a liter is equal to one microliter, abbreviated
 l.
You need a very accurate and precise instrument to measure such small volumes. The instrument most often used to measure microliters is called a micropipette. You will be using two types of micropipettes: a 0.5-10µl and a 10-100µl micropipette. You can distinguish them by the color of the cap on each pipette. A 0.5-10µl has a grey cap and a 10-100µl pipette has a yellow cap.
This challenge will help you become accustomed to using micropipettes. You have two tubes of colored water: green and yellow. Practice using the micropipettes by adding the amounts listed on the back of this paper to an empty microcentrifuge tube. Record which micropipette you used and the numerical setting as it appears in the window of pipette; darken the appropriate line to represent the decimal point. If the amount was greater than the micropipette can hold and you needed to use it multiple times, record the last setting as well as how many times you filled the micropipette to capacity.
Example:
Add the following amounts to an empty tube.
235
 l
Use this color water. Record which micropipette you used.
Green Yellow cap
Record the setting.
Darken the line representing the decimal point.
0
3
5
0
Copyright

2007 MassBioEd

Add the following amounts to an empty tube.
220
7
 l
74.4

 l l
.0183 ml
Use this color water. Record which
Green
Green
Yellow
Green micropipette you used.
Record the setting.
Darken the line representing the decimal point.
.583 ml Yellow
197
 l Yellow
.0047 ml Green
48.6
 l Yellow
347
 l Green
How many
 l should you have in test tube when you are finished?
How many ml should you have in the test tube when you are finished?
Can you think of a way to use the 10-100µl micropipette to check that the amount of liquid in your test tube is what it should be? Did you pipette the correct amount of liquid? If not, what happened?
Copyright

2007 MassBioEd

Each group of students needs a 0.5-10µl and 10-100µl micropipe as well as the correct tips for each micropipette. If p1000's are not available, you can modify the activity by having students skip the volumes above 200
 l, which are in the 1 st
, 5 th
, and 9 th
rows.
Answer
Correct pipetting will result in a final volume of 1500
 l or 1.5 ml . Students can check their pipetting accuracy in two ways:
1.
Most microcentrifuge tubes have marks at 0.5 ml, 1ml, and 1.5 ml. Their liquid should be at the level of the 1.5 ml mark, and the tube should be almost full.
2.
Students can measure the liquid in their tube with a 1ml pipette. Withdraw 1 ml of liquid from the tube. Expel it into a liquid waste container. Then withdraw the rest of the liquid in the tube into the pipette. It should read 0.5ml.
Copyright

2007 MassBioEd