# dilution question help - basic quick questions (Aug/15/2007 )

Is the logic correct:

You are told to make a 1:50 dilution of a 20ul volume of Sample A. Would I take 1ul out of this 20ul and raise it up with 49ul water? Is that what that means? Is this also called a 50 fold dilution?

If Sample B has 100ul in it and you are told to make a 20 fold SERIAL dilution from it, would you take 1ul of Sample B and raise it up with 19ul of water? Then, from this last tube, take 1 ul and raise that up again with 19ul water?

Thanks for any help.

-nk111-

QUOTE (nk111 @ Aug 15 2007, 10:43 AM)
You are told to make a 1:50 dilution of a 20ul volume of Sample A. Would I take 1ul out of this 20ul and raise it up with 49ul water? Is that what that means? Is this also called a 50 fold dilution?
Yes to both questions
QUOTE
If Sample B has 100ul in it and you are told to make a 20 fold SERIAL dilution from it, would you take 1ul of Sample B and raise it up with 19ul of water? Then, from this last tube, take 1 ul and raise that up again with 19ul water?

This is also correct. However, making dilutions with these low volumes is not very accurate and in a serial dilution, the errors accumulate so that the concentration of the lowest dilution may be very far from what you think it is. It is best to use as large a volume as possible - e.g. take 50ul (or even more if possible) of sample B into a final volume of 1mL for a 20-fold dilution.

-bitesizebio guy-