MICROPIPETTER CALIBRATION

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Background:

Before you start any type of lab work, it is a good idea to check the accuracy and precision of the micropipetters that you plan to use. A very simple way to do this is by weighing the volume of water actually transferred by a micropipetter at a given setting.   Water has a density of 0.9986 g/mL at room temperature, so you can use the mass of the water transferred to determine the accuracy of your pipetter (as long as your balance is reliable of course....), and by repeating the test several times, you can determine the precision of the micropetter as well..
Procedure:
1. Using a balance capable of reading in milligrams or lower, tare a plastic weighing boat on the pan of the balance.
2. Set the micropipetter to its maximum capacity and carefully transfer that volume of distilled water to the weighing boat.
3. Repeat the operation at least four times, each time recording  the weight of distilled water transferred.
4. Set the micropipetter to transfer 20 - 50% of its maximum volume and repeat step 3.
5. Calculate the average (x -bar) and the standard deviation (sigma) for each set of measurements, using the equation below (or the appropriate button on your calculator).


sigma = standard deviation; n = total number of measurements; xi= value of the ith measurement of x; x-bar = average value of x over n measurements.
 
6.  Fill out a copy of the table shown below for each of your micropipetters.
7. Assess the accuracy and precision of your micropipetters.
Your name ___________________________________________________
 Micropipetter # __________    Micropipetter Max. Vol.: __________ mL 

Vol.  setting:________ mL (max ) 
Vol. setting:________ mL ( ~¼ max ) 
Mass of dH2O (mg) Mass of dH2O (mg)

_______ 
_______ 

________ 
________ 

________ 
________ 

________ 
________ 

________ 
________ 

  Micropipetter # __________    Micropipetter Max. Vol.: __________ mL 

Vol.  setting:________ mL (max ) 
Vol. setting:________ mL ( ~¼ max ) 
Mass of dH2O (mg) Mass of dH2O (mg)

_______ 
_______ 

________ 
________ 

________ 
________ 

________ 
________ 

________ 
________ 

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