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Beer-Lambert Law:
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The molecular 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.
The calculator uses the Beer-Lambert law:
Where:
Explanation: The Beer-Lambert law describes the linear relationship between absorbance and the concentration of an absorbing species, with the extinction coefficient as the proportionality constant.
Details: The extinction coefficient is crucial for determining concentrations of unknown samples, characterizing new compounds, and in various analytical applications including biochemistry, chemistry, and environmental science.
Tips: Enter absorbance (typically measured at specific wavelength), concentration in mol/L, and path length in cm. All values must be positive and measured under the same experimental conditions.
Q1: What is the typical range for extinction coefficients?
A: Extinction coefficients typically range from 0 to over 100,000 L/mol-cm, depending on the compound and wavelength.
Q2: How does wavelength affect extinction coefficient?
A: Extinction coefficient is wavelength-dependent and is usually reported at the absorption maximum (λmax) of the compound.
Q3: What are the limitations of Beer-Lambert law?
A: The law assumes monochromatic light, non-interacting molecules, and no scattering or fluorescence. It may deviate at high concentrations.
Q4: How is extinction coefficient determined experimentally?
A: By measuring absorbance of solutions with known concentrations at a fixed path length and plotting absorbance vs. concentration.
Q5: What is the difference between molar and specific extinction coefficient?
A: Molar extinction coefficient uses concentration in mol/L, while specific extinction coefficient uses concentration in g/L or mg/mL.