Beer-Lambert Law

As we saw on the previous page, absorbance can be calculated from knowing the amount of radiation going into and coming out of the sample.

Absorbance can also be calculated through the Beer-Lambert Law:

A = ecl

A = the absorbance of radiation by the sample

e = the molar absorption coefficient (L mol^-1 cm^-1). This can also be thought of as a measure of the amount of radiation absorbed per unit concentration of the sample as the equation can be rearranged to: e = A / cl. This value is a constant for a particular substance.

c = the concentration of the sample (mol L^-1)

l = the path length of the cell which the sample is held in. This is the length that the radiation has to travel through (cm).