Question

find the dilution factor of the following protocol

Prepare the milk sample:

Dilute 0.5 mL of the pure milk sample to volume with phosphate buffer in a 10-mL volumetric flask. Mix the sample and transfer to a large test tube. Label this tube “milk dilution 1.”

Transfer 0.5 mL of milk dilution 1 to a 10-mL volumetric flask and dilute with phosphate buffer. Transfer to a test tube labeled “milk dilution 2.” You have just performed a serial dilution to dilute the milk sample.

Transfer 4.5 mL of CBBG dye to a clean, dry test tube.

Add 0.5 mL of milk dilution 2, mix carefully, and incubate for 10 minutes. Transfer to a cuvette.

Answer 1

Ans. #1. Milk Dilution 1:

Milk dilution 1 = Vol. of sample taken / Final volume of solution made upto

                                    = 0.5 mL / 10.0 mL

                                    = 0.5 : 10.0

                                    = 1 : 20

#2. Milk dilution 2:

Current Milk dilution = Vol. of sample taken / Final volume of solution made upto

                                    = 0.5 mL / 10.0 mL

                                    = 0.5 : 10.0

                                    = 1 : 20

Total dilution to make milk dilution 2 = Current dilution x Previous dilution

= Current dilution x Milk dilution 1

                                                            = (1 : 20) x (1 : 20)

                                                            = 1 : 400

# Final dilution:

Volume of milk dilution taken = 0.5 mL

Final volume made upto = 0.5 mL (milk dilution 2) + 4.5 mL (CBBG) = 5.0 mL

Current Milk dilution = Vol. of sample taken / Final volume of solution made upto

                                    = 0.5 mL / 5.0 mL

                                    = 0.5 : 5.0

                                    = 1 : 10

Total dilution to make final dilution: = Current dilution x Milk dilution 2

                                    = (1 : 10) x (1 : 400)

                                    = 1 : 4000