1. What is Molar Extinction Coefficient?

Definition: The Molar Extinction Coefficient (ε) measures how strongly a chemical species absorbs light at a particular wavelength.

Purpose: It's used in spectroscopy to determine concentrations of substances in solution using Beer-Lambert Law.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( ε \) — Molar extinction coefficient (m²/mol)
• \( m \) — Slope of the absorbance vs. concentration plot
• \( l \) — Path length/thickness of the cell (meters)

Explanation: The slope from a Beer's Law plot (absorbance vs. concentration) divided by the path length gives the molar extinction coefficient.

3. Importance of Molar Extinction Coefficient

Details: This value is crucial for quantitative analysis in spectroscopy, as it's a characteristic property of each substance at specific wavelengths.

4. Using the Calculator

Tips: Enter the slope from your absorbance vs. concentration plot and the cell path length (default 5.05×10⁻⁸ m for standard 1 cm cells). Path length must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for molar extinction coefficients?
A: They vary widely - from 10 to over 100,000 m²/mol depending on the substance and wavelength.

Q2: Why is the path length important?
A: Absorbance is directly proportional to path length, so accurate measurement is essential for correct ε calculation.

Q3: What units should the slope have?
A: The slope should be in absorbance units per molar concentration (AU/M or AU·L/mol).

Q4: Can I use this for any wavelength?
A: ε is wavelength-specific, so calculations must be done for each wavelength of interest.

Q5: How do I get the slope value?
A: Plot absorbance vs. concentration for several standard solutions and determine the slope of the best-fit line.