SOP For Using a Micropipette
To take small volumes with great accuracy
It is applicable to the microbiology laboratory
- Make sure that the pipette is in good condition.
- Check the micropipette by pre-wet the tips 2-3 times.
- After checking the pipette, adjust the desired volume which you want to take by rotating the volume setting ring of pipette.
- Set the representative tip for the Pipette.
- Press and hold the plunger of the pipette at the first stop.
- Place the pipette tip into the liquid which you want to take. Make sure that the pipette is insert in the liquid in the erect position.
- Slowly release the plunger of the pipette.
- Pause for a second so that no bubbles form in the tip.
- Move the tip from the liquid to the delivery vessel. Place the tip against the wall of the delivery vessel.
- Press the plunger to the second stop. Make sure that the pipette tip is inserted in erect position.
- Pause for 2 seconds and then release the plunger.
- Eject the tip into waste container by ejector
There are some precautions that need to remain in mind while using the micropipette.
- Always store the pipette in its maximum volume.
- Don’t use a pipette past its volume limits
- Don’t jam the pipette tip into the pipette.
- Calibrate the micropipette after every 3 months.
Calibration of micropipette
The calibration of the micropipette is done by using water samples at room temperature.
- Weigh the glass beaker at room temperature and tare it.
- Set the desired volume and take the water sample with the micropipette at the desired volume.
- Aspirate the volume and dispense it in an empty weighed glass beaker.
- Weigh the beaker and repeat this 10 times
- Then, take the mean of the weighs. And convert it into μL by using the formula
Volume = weight of water samples/density of water samples at 25°C
- After getting the weight in μL, calculate the percentage variation of micropipette by using the formula
% Variation =(100 x Actual weight – Observed weight)/D
- Calculate the Accuracy and Precision (% CV) as per the below formula-
Accuracy (%Error) = Mean – Set Volume x 100 / Set Volume
Precision (% CV) =Standard Deviation × 100 / Mean