Question

you have a series of 10 tubes. The first tube contains 0.1 mL saline. Tubes 2-10 contain 0.1 mL saline. O.01 mL serum is added to the first tube, and 0.05 mL is taken from the first tube and placed in the second tube where there is 0.1 mL of saline. A dilution using 0.05 mL is carried out in the remaining tubes.

What is the tube dilution and final dilution in tube 1?

What is the tube dilution in tube 2?

What is the final dilution in tube 2?

Answer 1

FIRST TUBE

Diluent in the first tube = 0.1ml saline

Sample added to the first tube = 0.01ml serum

Sample taken from the first tube = 0.05ml

Tube Dilution = Sample / Diluent + Sample (Sample = amount added, Diluent = amount already in the tube)

= 0.01 /0.1 + 0.01 = 0.01/0.11

= 0.09ml

Final Dilution = Sample added + Diluent - Sample removed

= 0.01 + 0.1 - 0.05

= 0.11 - 0.05 = 0.06ml

SECOND TUBE

Diluent = 0.1ml

Sample added = 0.05ml

Tube dilution = Sample / diluent + sample

= 0.05 / 0.1 + 0.05

= 0.05 / 0.15

= 0.33 ml

Final dilution = Sample + diluent

= 0.5 + 0.1

= 0.15ml