Micropipette Challenge Explanation
Micropipettes:
Micropipettes are precision instruments designed to measure and transfer small
volumes of liquids. They are expensive and must be used with care because their
accuracy is dependent upon their proper use. Pipettes vary in their volume range they
will measure, the type of tips they fit, and the way the volume is set. Be sure that
everyone understands how to operate the micropipettes. Don’t be afraid to ask if
you are unsure of any part of using a pipette.
The Golden Rules of Pipetting:
1. Don’t rotate the volume adjuster beyond the upper or lower range for the
volume of the pipette, this can damage the pipette.
2. Don’t use a pipette without an appropriate size tip on it. If this happens,
the liquid being transferred gets into the opening of the pipette and will
damage the mechanisms inside.
3. Don’t lay a pipette down that has a tip attached filled with liquid. If this
happens, the liquid being transferred gets into the opening of the pipette
and will damage the mechanisms inside.
4. Use new pipette tips between different samples in order to prevent
contamination.
Setting the volume:
All micropipettes have a volume control dial. Determine the volume of liquid that
you need to transfer and set the appropriate volume on the pipette using the dial control.
Make sure that you are reading the scale appropriately for the volume of the pipette that
you are using.
Parts of a micropipette:
a. Plunger button
b. Tip ejector button
c. Volume adjustment dial
d. Volume indicator
e. Shaft
f. Attachment point for a disposable tip
a
c/d
b
e
f
Drawing up and Expelling liquid:
The diagram below shows the correct operation of a micropipette.
1st stop: Depress plunger to the first stop.
2nd stop: Please note the location of the second stop on the pipette – We will not be using
this stop when transferring liquids using the pipettes. *If you go past the first stop, you
will draw too much liquid into the tip giving you an inaccurate volume.
Step 1: Immerse the tip into your tube just below the level of the liquid.
Step 2: Slowly release the plunger to draw the liquid into the tip. Do not release the
plunger too quickly, if you do you may introduce bubbles into your sample and you may
splash liquid onto the shaft of the pipette.
Step 3: Remove the tip from the sample liquid and place the tip against the wall of the
tube you are transferring your liquid into.
Step 4: Smoothly push the plunger to the first stop. Do not push the plunger down to the
second stop because you will “blow out” your sample which can cause contamination
between samples.
Step 5: Slowly raise the pipette out of the tube while slowly releasing the plunger,
making sure that you are not sucking up any of the liquid you just transferred.
Step 6: Press down the tip ejector knob to remove the disposable tip. Make sure you do
this over an appropriate trash receptacle so you do not contaminate your work area.
Step 7: Add a new tip and continue on to your next sample.
http://faculty.buffalostate.edu/wadswogj/courses/BIO211%20Page/Resources/micropipett
ing%20lab.pdf
Micropipette Challenge and Practice gel loading exercise
Micropipette challenge
Laboratory science often involves working with very small volumes of liquid; frequently
millionths of liters are used. 1 liter = 1,000 ml = 1,000, 000 µl. An example of how small
a µl is would be human tears. A human tear drop contains about 20 µl of fluid. It is very
difficult to measure these small volumes without a precise instrument, which is why a
micropipette is used.
To help you become familiar with how a micropipette functions you will be given some
food coloring to transfer to empty tubes. Notice how very small the volumes in fact are.
Discuss with your class what is considered good micropipette technique and how to use
the micropipettes properly.
Example:
Amount to add to tube
Color
15 µl
Red
Record the setting as it
appears in the window
15.0
Add the following amounts to an empty tube – all of the amounts should be transferred to
an empty tube.
Amount to add to tube
Color
Record the setting as it
appears in the window
12 µl
5 µl
10 µl
Practice gel loading exercise
“Loading gels”, or adding samples to the wells of a gel, can be a very challenging task
especially if you have never done it before. This exercise provides you an opportunity to
practice before you are asked to load the actual samples involved in the laboratory
activity. Take your time and figure out the method that works best for you (everyone
pipettes differently according to their comfort level).
Remember that the wells appear to be holes but they really aren’t. They are more like
indentations in the gel that do not go through completely to the bottom of the gel. That is
why it is very important not to poke the micropipette tip through the bottom of the gel or
else your sample will seep out of the gel and into the surrounding container.
You may also find it helpful to load the gel at an “angle” as shown in the picture below in
order to better see your sample being loaded into the gel.
Remember to review the techniques for using the micropipette from the micropipette
challenge explanation. You may want to have those handy to refer back to while
practicing sample loading.