1. What is Serial Dilution?

Serial dilution is the stepwise dilution of a substance in solution. Each step uses the previous dilution as the starting point, resulting in an exponential decrease in concentration. This technique is widely used in microbiology, biochemistry, and analytical chemistry.

2. How Serial Dilution Works

The serial dilution process follows this formula at each step:

Where:

• \( C_1 \) — Initial concentration
• \( C_2 \) — Final concentration after dilution
• \( D \) — Dilution factor (e.g., 10 for 1:10 dilution)

Example: Starting with 100 mg/mL and doing 1:10 serial dilutions:

• Step 1: 100/10 = 10 mg/mL
• Step 2: 10/10 = 1 mg/mL
• Step 3: 1/10 = 0.1 mg/mL

3. Applications of Serial Dilution

Common Uses:

• Creating standard curves for assays
• Determining microbial counts
• Preparing samples for analysis
• Drug dose-response studies
• Antibiotic susceptibility testing

4. Using the Calculator

Instructions:

1. Enter the initial concentration (e.g., 100 mg/mL)
2. Set the dilution factor (e.g., 10 for 1:10 dilutions)
3. Specify how many dilution steps you need
4. Click Calculate to see the concentration at each step

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between serial and simple dilution?
A: Serial dilution uses each dilution as the starting point for the next, while simple dilution always starts from the original stock.

Q2: Why use serial dilution instead of making each dilution separately?
A: Serial dilution is more efficient when creating multiple dilutions and requires less of the original stock solution.

Q3: How accurate are serial dilutions?
A: Accuracy depends on precise pipetting technique. Errors compound with each step, so careful technique is essential.

Q4: What's the maximum practical number of dilution steps?
A: Typically 6-8 steps for 1:10 dilutions, as concentrations become extremely small beyond this.

Q5: Can I do non-integer dilution factors?
A: Yes, though integer factors (2, 5, 10) are most common. The calculator works with any factor >1.