Question

How do you calculate concentration from absorbance?

Answer 1

As we know that Beer’s law state that when a monochromatic light is allowed to passed through a transparent medium, then there is decrease in the intensity of the light having the thickness of the absorbing medium is directly proportional to the concentration of the solution and the intensity of the light.

Complete answer:
- It is found that by combining Lambert's law and Beer's law, we get a law called Lambert-Beer's law. This law states that for a given material the concentration and the path length are directly proportional to the absorbance of the light. This law is found to have many wide applications in the field of medicine, and to test with quantification.
- We can write the expression for Lambert-Beer’s law as:
$A=\in Cl$
- Where, A is the absorbance, C is the concentration, l is the path length that is the length of the absorbing medium and $\in$ is the molar absorption coefficient. Here, from the formula we can see that if we know the value of the concentration and path length then we can calculate the absorbance.
- Hence, we can conclude that we can calculate concentration from absorbance from the Lambert-Beer’s law equation that is $A=\in Cl$

Note:
- It is found that the relation given by Beer’s law can be used to determine the concentration of the species present in the solution by using a spectrophotometer or colorimeter.
- It is found that more is the absorptivity, more is the electronic transition state.