Biology Forum › Microbiology › Why is it allowable to use the same pipette tip??
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- May 6, 2008 at 7:35 pm #9598
angelyn1985ParticipantI wonder why it is allowable to use the same pipette tip for bacterial count on plates if we start with the lowest dilution and then the next lowest dilution??
- May 6, 2008 at 7:38 pm #83942CatParticipant
If you start with the lowest concentration and go to the highest, carryover amount is negligible.
- May 6, 2008 at 7:39 pm #83943angelyn1985Participant
I see! Thanks!!
- May 6, 2008 at 7:41 pm #83944canalonParticipant
Simply because the amount of bacteria from the diluted sample is negligible compared to the amount in the next tube. With 10 fold dilution, even if you were to plate the totality of the lower dilution there would be less than 10% error. Since it is likely that you will in fact empty closer to 99%of the volume in your tip, that makes an error closer to 0.1%. This is lower than the accuracy of most pipettes. Ergo, save yourself some work, and some tips.
- May 6, 2008 at 7:53 pm #83945MrMisteryParticipant
Lol… This thread reminds me… I once worked with 24 flasks using the same pipette. Talk about saving….
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