In performing an immunological procedure, you add 2 mL of serum to 8 mL of saline. Two 1:2 serial dilutions are then made. What is the dilution of serum contained in the final tube?
To determine the dilution of serum contained in the final tube, we need to follow the dilution steps provided in the question.
1. Initially, you add 2 mL of serum to 8 mL of saline, resulting in a total volume of 10 mL (2 mL + 8 mL). The serum is now diluted in a 1:5 ratio (2 mL serum / 10 mL total volume).
2. Next, you make two serial dilutions, each with a 1:2 ratio. This means that each dilution step will reduce the concentration by half.
The first serial dilution:
- Take 1 mL of the 1:5 diluted serum from step 1 and add it to 1 mL of saline.
- The resulting total volume is 2 mL.
- This dilution reduces the concentration by half, so the new dilution is 1:10 (1/2).
The second serial dilution:
- Take 1 mL of the 1:10 diluted serum from the first serial dilution and add it to 1 mL of saline.
- The resulting total volume is 2 mL.
- This dilution also reduces the concentration by half, so the new dilution is 1:20 (1/2).
Therefore, the dilution of serum contained in the final tube is 1:20.