1. What is Serial Dilution?

Serial dilution is a stepwise dilution of a substance in solution. It is commonly used in microbiology to reduce the concentration of cells to a countable range for accurate enumeration and analysis.

2. How Does the Calculator Work?

The calculator uses the serial dilution formula:

Where:

• \( C_n \) — Final concentration after n dilution steps (cells/mL)
• \( C_0 \) — Initial concentration (cells/mL)
• \( n \) — Number of 10-fold dilution steps

Explanation: Each dilution step reduces the concentration by a factor of 10, making it easier to count cells and determine original concentrations.

3. Importance of Serial Dilution

Details: Serial dilution is essential for obtaining countable cell numbers on agar plates, preparing standard curves, and performing accurate quantitative microbiological analyses.

4. Using the Calculator

Tips: Enter the initial cell concentration in cells/mL and the number of 10-fold dilution steps. Both values must be valid (concentration > 0, steps ≥ 0).

5. Frequently Asked Questions (FAQ)

Q1: Why use 10-fold serial dilutions?
A: 10-fold dilutions provide a practical and systematic approach to reduce cell concentrations to countable ranges while maintaining accuracy and reproducibility.

Q2: What is a typical initial concentration range?
A: Initial concentrations typically range from 10⁶ to 10⁹ cells/mL, requiring 4-7 dilution steps to reach countable ranges of 30-300 colonies per plate.

Q3: How do I ensure accurate dilution?
A: Use precise pipetting techniques, mix thoroughly after each dilution, use fresh pipette tips for each transfer, and maintain sterile conditions.

Q4: Can I use different dilution factors?
A: Yes, while 10-fold is standard, other factors (2-fold, 5-fold) can be used depending on the specific application and required precision.

Q5: What are common applications?
A: Bacterial enumeration, viral titer determination, antibiotic susceptibility testing, and preparation of standard solutions for various assays.