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Beer-Lambert Law:
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The molar absorption coefficient (ε), also known as molar absorptivity or extinction coefficient, is a measure of how strongly a chemical species absorbs light at a given wavelength. It is a fundamental property in spectroscopy and quantitative analysis.
The calculator uses the Beer-Lambert Law:
Where:
Explanation: The Beer-Lambert Law describes the linear relationship between absorbance and concentration of an absorbing species in solution.
Details: The molar absorption coefficient is crucial for quantitative analysis in spectroscopy, determining unknown concentrations, characterizing compounds, and validating analytical methods in chemistry and biochemistry.
Tips: Enter absorbance (unitless), concentration in mol/L, and path length in cm. All values must be valid (absorbance ≥ 0, concentration > 0, path length > 0).
Q1: What are typical values for molar absorption coefficients?
A: Values range from near zero for weak absorbers to over 100,000 L/mol·cm for strong chromophores. Most organic compounds range from 1,000 to 50,000 L/mol·cm.
Q2: Does molar absorption coefficient depend on wavelength?
A: Yes, ε is wavelength-dependent and is typically reported at the wavelength of maximum absorption (λmax).
Q3: What factors affect molar absorption coefficient?
A: Temperature, solvent, pH, and molecular structure all influence ε values. It is generally constant for a given compound under specific conditions.
Q4: How is this different from specific absorption coefficient?
A: Molar absorption coefficient uses molar concentration, while specific absorption coefficient uses mass concentration (g/L or mg/mL).
Q5: What are the limitations of Beer-Lambert Law?
A: The law assumes monochromatic light, dilute solutions, no scattering, and no chemical associations. Deviations occur at high concentrations.