How To Use Micropipettors Jan. 15, 2015

A Micropipettor is a laboratory equipment. It is used to measure and transfer small volumes (1microliter and less) of liquids. To obtain precise results of an experiment you have to know the parts of a micropipettor:

1. Three sizes of micropipettes. The sizes are noted on the top of the plunger button. Neither upper nor lower limits sould be ever exceeded. The size of an instrument you can find the top of the plunger button.

 Size Micropipette

Range of limits measured

 P20:

0.5 to 20 microliters

 P200:

20 to 200 microliters

 P1000:

100 to 1000 microliters

2. Set the needed  volume by turning the centrally located rings clockwise to increase volume or counterclockwise to decrease volume.

P20: Maximum volume 20 microliters. Accurate between 5 and 20 microliters. Numbers on the micropipetter (typically black/black/red) are read as XX.X microliters. The change in color indicates the position of the decimal point.
P200: Maximum volume 200 microliters. Accurate between 20 and 200 microliters. Numbers on the micropipetter (one color) are read as XXX microliters.
P1000: Maximum volume 1000 microliters (= 1 milliliter). Accurate between 200 and 1000 microliters. Numbers on the micropipetter (typically red-black-black) are read X.XX !milliliter!. Note that this micropipetter reads milliliters while the other two read microliters.

The example below show how to read the micropipettor:

 P1000

 P200,100

P20

1

1000’s

2,1

100’s

2

10’s

0

100’s

0

10’s

0

1’s

0

10’s

0

1’s

0

1 decimal


3. Place a tip on the discharge end of the pipettor. If sterile conditions are necessary you should not let the pipet tip touch any object around or even your hands.

4. While depressing the plunger it will stop at two different positions. The first stopping position is the point of initial resistance and is the level of depression. It will result in the needed volume of liquid being transferred. This first stopping position is dependent on the volume that is being transferred. That’s why the distance along which you have to push the plunger to reach the point of initial resistance will change depending on the volume being pipetted. The next stopping position you can find when the plunger is depressed beyond the initial resistance until it is in contact with the body of the pipettor. At this position the plunger cannot be further depressed (this second stopping position is used for the complete discharging of liquids from the plastic tip); when drawing liquid into the pipettor you should not reach this second stop, only when expelling the last drop. Try to practice depressing the plunger to each of these stopping positions until you easily distinguish between these points, before continuing.

5. The tip of a pippetter, before drawing a liquid in, should be put into the liquid just slightly below the surface as shown below.


NOTES:

  • Never point a pipettor up. This may cause liquid to run down into the pipettor destroying it.
  • When withdrawing liquids with the pipettor, always release the plunger slowly. This prevents liquid from rushing into the end of the pipette and clogging it up. This is especially important with large volume pipettors (200-1000 microliters).
  • Be sure you use the proper size tip for each pipettor.
  • Always use a new tip for each different liquid.
  • Use the correct pipettor for the volume that is to be dispensed. Never use the 200-1000 microliters pipette to dispense volumes below 200 microliters. Going below or above the range of the micropipettor may damage the instrument.

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