1. What Is The Extinction Coefficient?

The extinction coefficient (ε) is a measure of how strongly a chemical species absorbs light at a particular wavelength. It is a fundamental parameter in spectrophotometry and is used to quantify the concentration of substances in solution using the Beer-Lambert Law.

2. How Does The Calculator Work?

The calculator uses the Beer-Lambert Law equation:

Where:

• \( \varepsilon \) — Extinction coefficient (M⁻¹ cm⁻¹)
• \( A \) — Absorbance (unitless)
• \( c \) — Concentration (mol/L)
• \( l \) — Path length (cm)

Explanation: The extinction coefficient represents the absorbance of a 1 M solution in a 1 cm path length cuvette at a specific wavelength.

3. Importance Of Extinction Coefficient

Details: The extinction coefficient is crucial for determining concentrations of unknown samples, characterizing chemical compounds, and is widely used in biochemistry, analytical chemistry, and pharmaceutical sciences.

4. Using The Calculator

Tips: Enter absorbance (typically between 0.1-1.0 for accurate measurements), concentration in mol/L, and path length in cm (standard cuvettes are 1.0 cm). All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for extinction coefficients?
A: Extinction coefficients vary widely by compound, ranging from ~1,000 M⁻¹ cm⁻¹ for small molecules to over 100,000 M⁻¹ cm⁻¹ for proteins with chromophores.

Q2: Does extinction coefficient depend on wavelength?
A: Yes, extinction coefficients are wavelength-specific and are typically reported at the wavelength of maximum absorption (λmax).

Q3: How is this different from molar absorptivity?
A: Extinction coefficient and molar absorptivity are often used interchangeably, though extinction coefficient is more general and can refer to different concentration units.

Q4: What affects the accuracy of extinction coefficient measurements?
A: Factors include solvent composition, temperature, pH, instrument calibration, and ensuring absorbance readings are within the linear range of the instrument.

Q5: Can this calculator be used for proteins?
A: Yes, but note that protein extinction coefficients are often calculated theoretically from amino acid composition or measured experimentally for accuracy.