Chemistry dilutions

Question

You’re preparing an Ouchterlony plate to test a blood sample from a crime scene to determine if it is of human origin. When diluting your samples, you plan to have the following dilutions of blood to water: 1:10, 1:100, 1:1,000, 1:2,000, and 1:10,000. You need 100μL of each dilution. Provide the volume of blood and water for each of the dilutions you will have to prepare.

Answer 1

1:10 = 10 ul blood + 90 ul H2O

1:100 = 10 ul of 1:10 + 90 ul H2O

1:1000 = 10 ul of 1:100 + 90 ul H2O

1:2000 = 50 ul of 1:1000 + 50 ul H2O

1:10,000 = 20 ul of 1:2000 + 80 ul H2O

NOTE: All these dilutions result in 100 ul, but you will not have 100 ul after using some to make the next dilution. If you want to have 100 ul left over after making all dilutions, you need to state that in the question. That calculation is significantly more complex, and the easier way would be to use direct dilutions, and not serial dilutions.