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How to Perform a Micropipettor Accuracy and
Precision Check
You will need:
- Analytical Balance (electronic auto-tare preferred) of suitable sensitivity
(see table below)
- Thermometer
- Weighing Vessel (5 mL capacity) with lid
- Distilled Water
Pipettor Max
Volume (mL) |
Sensitivity
(mg) |
| 1000 |
0.1 |
| 100 |
0.1 |
| 10 |
0.01 |
| 1 |
0.001 |
Procedure:
- Place about 1 mL of water inside the weighing vessel, while keeping your
hands and the outside of the weighing vessel dry.
- Tare the container (i.e. "zero" the balance)
- Record the test water temperature. The ideal temperature is 20±1°C.
- Aspirate the water from the reservoir.
- Check that the balance is at zero.
- Remove the weighing vessel from the balance, remove the lid, deliver the
test water into the vessel, recap and weigh. Record the weight.
- Repeat the procedure for a total of 10 samples.
- Try to maintain a standard timed technique (i.e. an experienced operator
will make one weighing every 15-20 seconds.)
- Check the water temperature again and correct for the variation of density
of pure water. Refer to the table below.
Temperature
(°C) |
Density
(g/mL) |
Temperature
(°C) |
Density
(g/mL) |
| 16 |
0.99894 |
21 |
0.99800 |
| 17 |
0.99877 |
22 |
0.99777 |
| 18 |
0.99860 |
23 |
0.99754 |
| 19 |
0.99841 |
24 |
0.99730 |
| 20 |
0.99820 |
25 |
0.99700 |
- Using a scientific calculator, calculate the mean, standard
deviation and coefficient of variation.
- Refer to the following table to determine whether or not the
micropipettor needs to be recalibrated.
Micropipettor Technical Data
| Catalog Number |
Volume Range
(΅L) |
Accuracy
(΅L) |
% Precision
(%) |
| E8-4301 |
220 |
2 +/ 4.0
10 +/ 1.0
20 +/ 0.8 |
<= 3.0
<= 0.7
<= 0.4 |
| E8-4302 |
20200 |
20 +/ 1.2
100 +/ 1.0
200 +/ 0.6 |
<= 0.6
<= 0.3
<= 0.3 |
| E8-4303 |
1001000 |
100 +/ 0.9
500 +/ 0.7
1000 +/ 0.6 |
<= 0.45
<= 0.25
<= 0.25 |
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