Question

what is a molar extinction coefficient? what are the typical units for this quantity? what factors will affect the molar extinction coefficient value?

Answer 1

The Beer-Lambert law (or Beer's law) is the linear relationship between absorbance and concentration of an absorbing species.

According to this law:

The equation is: A = ebc.

Here e = molar absorbtivity, in L/mol *cm

b = cell path length in cm,

and c = concentration in moles/liter or M

and

A = log (1/T)

Molar extinction coefficient is a measure of how strongly a substance absorbs light at a particular wavelength, and is usually represented by the unit M-1 cm-1 or L mol-1 cm-1.

Molecular extinction coefficient or molar absorptivity at a particular wave length , is a measure of the intensity of absorption at a particular wavelength and given concentration of the compound. It is depend on the following factors:

1. Concentration of solution
2. Wavelength
3. Length of the cell