Question

1. A 25ul aliquot of cells was diluted with 75ul of PBS. An aliquotof the diluted cells was diluted 1:2 using 25ul of trypan. What is the total cell dilution factor?

2. A 25ul aliquot of cells was diluted with 75ul of PBS. An aliquot of the diluted cells was diluted 1:2 using 25ul of trypan.What was the volume(ul) of diluted cells used?

Answer 1

Ans. #1. 1^st dilution: Total volume made upto = 25 uL + 75 uL = 100 uL

Immediate dilution factor (IDF 1) for 1^st dilution = Vol. of aliquot / Total vol. made upto

                                                                        = 25 uL / 100 uL

                                                                        = ¼ = 0.25

Let’s label the final solution after 1^st dilution as solution 1.

# 2^nd dilution: Solution 1 is diluted 1: 2

So, Immediate dilution factor (IDF 1) for 2^nd dilution = 1 : 2 = 0.5

# Now, total dilution factor (TDF) = (IDF 1) x (IDF 2) = (1/4) x (1/2) = 1/8 = 0.125

                                    Or, TDF = 0.25 x 0.50 = 0.125 = 1/8                                            

#2: Let the volume of diluted cells used be X uL

So,

            Total volume made upto = X uL + 25 uL = (X + 25) uL

Now,

            Immediate dilution factor (IDF) = Vol. of aliquot / Total vol. made upto

            Or, ½ = X uL / (X + 25 uL) = X / (X + 25)

            Or, X + 25 = 2X

            Or, 2X- X = 25

            Hence, X = 25

Therefore, required volume of diluted cells = X uL = 25 uL