1. What Is The Molar Extinction Coefficient?

The molar 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 that quantifies the absorbance of a solution per unit concentration and path length.

2. How Does The Calculator Work?

The calculator uses the Beer-Lambert Law:

Where:

• \( \varepsilon \) — Molar extinction coefficient (L/mol·cm)
• \( A \) — Absorbance (unitless)
• \( c \) — Concentration (mol/L)
• \( l \) — Path length (cm)

Explanation: The equation relates the attenuation of light to the properties of the material through which the light is traveling, specifically the concentration of the absorbing species and the path length.

3. Importance Of Extinction Coefficient

Details: The molar extinction coefficient is crucial for determining concentrations of unknown samples, comparing the light-absorbing abilities of different compounds, and is widely used in biochemical assays, pharmaceutical analysis, and environmental testing.

4. Using The Calculator

Tips: Enter absorbance (typically measured at a specific wavelength), concentration in mol/L, and path length in cm. All values must be positive numbers. The path length for standard cuvettes is typically 1.0 cm.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical range for extinction coefficients?
A: Extinction coefficients vary widely depending on the compound. Small molecules typically have values from 10 to 100,000 L/mol·cm, with many biological chromophores in the 5,000-15,000 range.

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

Q3: How is this different from absorption coefficient?
A: The molar extinction coefficient is specific to concentration in mol/L, while absorption coefficient may refer to different concentration units (e.g., mg/mL or % w/v).

Q4: What factors affect the accuracy of this calculation?
A: Measurement accuracy depends on proper instrument calibration, using the correct wavelength, avoiding concentrations that are too high (which can cause deviations from the Beer-Lambert Law), and ensuring the solution is homogeneous.

Q5: Can this calculator be used for proteins?
A: Yes, but proteins are typically measured using specific extinction coefficients calculated from their amino acid composition, particularly tryptophan and tyrosine content.