Study Notes: Use of Pipettes
- Open the packet or container of sterilised pipettes so that
the cotton wool plugged end is just exposed.
- Place pipette bulb if using a Pasteur pipette or a pipette
filler if using a graduated pipette onto the plugged end of the
- Carefully withdraw the pipette making sure that the sterile
tip does not touch the bench, other equipment or you.
- Fill the pipette with the liquid you are sampling. Do this
by squeezing the bulb before you insert the tip into the liquid
or if using a pipette filler, place the tip into the liquid and
raise the fluid level using the filler.
- Transfer the tip of the pipette to the medium to be inoculated,
eg an agar plate, and deliver the liquid by either squeezing the
bulb or lowering the level of fluid with the pipette filler.
- If using a bulb keep the bulb depressed and discard the Pasteur
pipette into a biohazardous sharp waste. If using a pipette filler,
remove the filler and place the graduated pipette into a disinfectant
- Never use a pipette that has a wet cotton wool plug. The plug
only prevents contamination if it is dry.
- Prevent aerosol production which can spread microorganisms.
Reduce or eliminate bubbles as bursting bubbles cause aerosols.
- Make sure you use a good fitting clean bulb or clean pipette
filler in good working order. This will ensure control of liquid
- Do not over fill the pipette and draw liquid into the bulb or
pipette filler, as this will cause contamination of the liquid.
If this happens dispose of the liquid, pipette and the bulb or
pipette filler will need to be disinfected and cleaned.