1. 1 ml serum added to 5 ml saline. 1:2 dilution is made. What is the dilution of serum in tube 6?

Question

So the serum + saline would make a 1:6 dilution. Multiply that by serial dilution of 1:2 which would give: (1/6) x (1/2) x (1/2) x (1/2) x (1/2) x (1/2) = (1/192). Is that correct?

2. How would you set up a series of tubes with a 1:4 dilution such that you end up with 3 ml in each tube?

Mm...this one I'm kind of stuck =/

Answer 1

I thought someone would have answered this already.

(1/2^n)*original concentration=concentration in tube 6
n=the number of times that you performed the 1:2 dilution.

For number 2, I am not sure about how to handle this, but I believe that you would remove 1 mL from the stock solution and add 3 mL of saline, repeating until the sixth tube.

I hope this helps.