Materials

  • Lab coat
  • Eye protection
  • Benchkote if necessary
  • Disinfectant and paper towels
  • Discard jar with disinfectant
  • Bunsen burner and mat
  • Labels
  • 7 sterile 1 cm3 syringes or pipette tips
  • 7 sterile test tubes or bottles each containing 9 cm3 diluent
  • Broth culture of yeast or bacteria to be diluted

Instructions

  1. Wear a lab coat and use eye protection.
  2. Label the test tubes or bottles with the appropriate dilution, 10 -1 – 10 -7.
  3. Make sure that the lid of the culture tube is firmly attached then shake the culture vigorously to separate clumps of cells and to distribute the organisms evenly throughout the liquid.
  4. Remove a sterile syringe or pipette tip from its pack/container. Do not touch the parts which will come in contact with organism. If using a pipette tip, carefully attach to the dispenser.
  5. Using aseptic technique (i.e. flaming the neck of the tube or bottle after removal and before replacement of its lid), remove exactly 1 cm3 of the fluid and transfer to the dilution tube next in the series.
  6. Place syringe or pipette tip into discard jar.
  7. Mix the dilution well.
  8. Repeat steps 4 – 7 until the last dilution tube is reached.

This process dilutes the organisms in the original sample to a countable number.