1. What is CFU/ml Calculation?

CFU/ml (Colony Forming Units per milliliter) calculation is a standard method used in microbiology to estimate the number of viable bacteria or fungal cells in a gas sample. It provides a quantitative measure of microbial concentration.

2. How Does the Calculator Work?

The calculator uses the CFU/ml formula:

Where:

• \( C \) — Colonies counted (unitless)
• \( DF \) — Dilution factor (unitless)
• \( V \) — Volume plated (ml)

Explanation: The formula calculates the concentration of viable microorganisms by accounting for the dilution factor and the volume of sample plated.

3. Importance of CFU/ml Calculation

Details: Accurate CFU/ml calculation is essential for microbial quantification in environmental monitoring, food safety testing, pharmaceutical quality control, and research applications involving gas samples.

4. Using the Calculator

Tips: Enter the number of colonies counted, the dilution factor used, and the volume plated. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is an appropriate dilution factor range?
A: Dilution factors typically range from 1:10 to 1:1,000,000 depending on the expected microbial concentration in the gas sample.

Q2: How many colonies should be counted for accuracy?
A: Ideally, count between 30-300 colonies per plate for statistical reliability. Counts outside this range may be less accurate.

Q3: What volume is typically plated?
A: Standard volumes range from 0.1 ml to 1.0 ml, depending on the protocol and expected microbial concentration.

Q4: Are there limitations to this calculation?
A: This method assumes each colony arises from a single cell, which may not account for cell clumping. It also only counts viable, culturable cells.

Q5: How should results be reported?
A: Report as CFU/ml with appropriate significant figures, typically rounded to 1-2 decimal places for scientific reporting.