Molar Extinction Coefficient

A substance's molar extinction coefficient value tells us something about how well that substance stops light from traveling through a solution it is part of. The absorbance of light energy as it travels through a solution is known as attenuation.

Extinction coefficients are wavelength dependent; the same substance can have different extinction coefficient values at different wavelengths.

Usually, a substance will exhibit maximum absorbance ability at a particular part of the spectrum. These peak absorbance values most commonly represent the most useful wavelengths for measuring a substance in solution. When using absorbance data to calculate concentration, we must ensure that the wavelength used to measure the substance matches with the wavelength used to generate the extinction coefficient.