Study Notes: Use of Pipettes

1. Open the packet or container of sterilised pipettes so that the cotton wool plugged end is just exposed.
   
   
2. Place pipette bulb if using a Pasteur pipette or a pipette filler if using a graduated pipette onto the plugged end of the pipette.
   
   
3. Carefully withdraw the pipette making sure that the sterile tip does not touch the bench, other equipment or you.
   
   
4. 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.
   
   
5. 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.
   
   
6. 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 container.
   

Safety Precautions

• 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 delivery.
• 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.
  

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