Molar Absorptivity Calculator | Beer-Lambert Law

Molar Absorptivity Calculator

Calculate the molar absorptivity constant (ε) using the Beer-Lambert Law equation: ε = A / (c × l)

unitless
cm

About Molar Absorptivity

Molar absorptivity (ε), also known as the molar extinction coefficient, is a measure of how strongly a chemical species absorbs light at a given wavelength. It is a fundamental parameter in spectrophotometric analysis and is used in the Beer-Lambert Law.

Beer-Lambert Law Formula

A = ε × c × l

Where:

  • A = Absorbance (unitless)
  • ε = Molar absorptivity constant (L·mol-1·cm-1)
  • c = Concentration of the solution (mol/L)
  • l = Path length through which light passes (cm)

What is Molar Absorptivity?

Molar absorptivity, also known as the molar extinction coefficient (ε), is a fundamental parameter in spectroscopy that measures how strongly a chemical substance absorbs light at a specific wavelength. It is expressed in units of L/(mol·cm) and serves as a characteristic property of a substance at a given wavelength.

This constant plays a crucial role in the Beer-Lambert Law, which establishes the relationship between absorbance, concentration, and path length. The law is expressed as A = ε × l × c, where A represents absorbance (unitless), ε is the molar absorptivity, l is the path length (cm), and c is the concentration (mol/L).

The value of molar absorptivity varies widely depending on the substance. Weakly absorbing compounds may have values close to zero, while strongly absorbing compounds can exceed 100,000 L/(mol·cm). This property is particularly important in analytical chemistry, biochemistry, and pharmaceutical research for quantitative analysis of compounds in solution.

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