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Appendix 4. Two-fold serial dilutions


A two-fold dilution reduces the concentration of a solution by a factor of two that is reduces the original concentration by one half. A series of two-fold dilutions is described as two-fold serial dilutions. In this manual, two-fold serial dilutions are carried out in small volumes in microwell plates. They are used in both the haemagglutination and haemagglutination inhibition tests to establish titres of the test samples.

A two-fold dilution

Step 1.

Use the micropipette to dispense 25 mL of PBS diluent to the first well.

Step 2.

Use the micropipette to transfer 25 mL of the test solution to the first well.

Step 3.

Use the micropipette to mix by drawing up the liquid and expelling it again. Carry out this action twice.

Step 4.

The well now contains 25 mL of the original test solution diluted by one half in a total volume of 50 mL.

Figure 24: A two-fold dilution

Two-fold serial dilutions

Step 1.

Use the micropipette to dispense 25 mL of the PBS diluent to all the wells across a row of a microwell plate.

Step 2.

Use the micropipette to transfer 25 mL of the test solution to the first well and mix. This is the first two-fold dilution.

Step 3.

Use the micropipette with the same tip to carry out a second two-fold dilution.

Step 4.

Continue the series of two-fold dilutions until the second last well of the microwell plate. The last well is used as a control well in the haemagglutination and haemagglutination inhibition tests.

Figure 25: Two-fold serial dilutions


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