Micropipette Lab
Comparing Precision and
Accuracy!
Cornell Notes & INB’s
Q column:
1. Students write
questions from
notes
2. Everything in
this column
should be a
question
 S - Set up the paper
 T - Take Notes
 A - After class
process the notes
 3 summary statements
 1 questions
 R - Reflect / review
Precision
The precision of a measurement
describes the “units” used to measure
something
The smaller the unit, the more precise!
Example of Precision
Ruler #1 can measure in centimeters
QuickTime™ and a
decompressor
are needed to see this picture.
“The pencil is a little over 9 cm”
Ruler #2 can measure in millimeters
QuickTime™ and a
decompressor
are needed to see this picture.
“The pencil is a little over 95 millimeters
Which ruler is more precise???
Ruler #2
Which tool can measure volume
more precisely?
QuickTime™ and a
decompressor
are needed to see this picture.
10 ml, 50 ml, or 100 ml
graduated cylinder?
How about
compared to
this tool?
Quic kT ime™ and a
dec ompres s or
are needed to s ee this pi cture.
20µL =
.020 ml
Accuracy
The difference between your
measurement and the “accepted” value
The bigger the difference, the less
accurate you were!
Examples of Accuracy
Bob measured this container of milk
And determined that it is 5.5 gallons
Bob wasn’t very accurate!
QuickTime™ and a
decompressor
are needed to see this picture.
Maria measured this container of milk
And determined that it is 1.1 gallon
Maria was very accurate!
Mai measured this container of milk
And determined that it is 3.7854118
Liters
= 3.7854118 liters
Mai was accurate and precise!
= 1 gallon
These are accepted values
Rules when using a micropipette
Gently remove the disposable tip by
depressing the button (not the top)
Never use a micropipette without a tip
Rules for using a micropipettor:
o Gently remove the disposable tips with your fingers.
o Never use the micropipetto r without a tip. This could cause damage
to the instrument.
o Never lay a loaded pipette down or til t it s ideways because this could
allow liquid to run back into the instrument.
o Never let the button snap back into place. Always allow it to rise
slowly back into position.
Never lay a loaded pipette down or tilt it
sideways because this could allow liquid
to run back into the instrument
Never let the button snap back into
place, always allow it to rise slowly back
into position
Let’s practice!
 Gently add a tip by pushing it onto the end of
the pipette
 Slowly turn the top knob to set the desired
measurement
 200 is 200, 20 is 020 (large volume pipette)
 20 is 200, 2 is 020 (small volume pipette)
 Slowly depress top knob down until you reach
the “first stop”
 Slowly put tip of pipette into water and slowly
release knob
 Depress top knob until you reach to “second
stop” to release liquid
Precisio
n
QuickTime™ and a
decompressor
are needed to see this picture.