If you prepared a serial dilution of protein standards mixin

If you prepared a serial dilution of protein standards, mixing 20L of protein with 80L of water and had a starting protein concentration of 500mg/mL, what are the final concentrations in each dilution tube (assuming 3 dilutions)?

Solution

Starting stock concentration is 500mg/ml and the final working volume of the solution is 100ul.

We will use the formula:

Stock concentration (C1) x Stock Volume (V1) used = Final concentration (C2) x Final volume (V2) of the solution

For first dilution,

C1 = 500 ml/ml; V1 = 20 ul; C2 = ; V2 = 100 ul

therefore, 500 mg/ml x 20 ul = C2 x 100 ul

C2 = 500 mg/ml x 20 ul / 100 ul

C2 = 100 mg/ml

Now, for serial (second) dilution,

C1 = 100 ml/ml; V1 = 20 ul; C2 = ; V2 = 100 ul

therefore, 100 mg/ml x 20 ul = C2 x 100 ul

C2 = 100 mg/ml x 20 ul / 100 ul

C2 = 20 mg/ml

For third dilution,

C1 = 20 ml/ml; V1 = 20 ul; C2 = ; V2 = 100 ul

therefore, 20 mg/ml x 20 ul = C2 x 100 ul

C2 = 20 mg/ml x 20 ul / 100 ul

C2 = 4 mg/ml