BEER’S LAW

Beer’s law can also be called Beer-Lambert law. Beer’s law is a simplified equation that relates diminution of the light to the properties of a specific material.  The beer’s law states that the chemical concentration used is directly proportional to specific solution absorbed. The relationship between the chemical concentration and solution is used to decide the chemical species concentration in a specified solution with the use of a spectrophotometer. Beer’s law is simply written as A=έbc. Where  A represents the absorbance, έ  the molar absorptivity, b the path length of a sample and ca concentration of a compound solution. When calculating absorbance, you have to consider the following assumptions. The first assumption is that  absorbance is quite directly proportional to a length of a path of a  particular sample which can be expressed as A άc(1.1) Aάc and the second assumption is that the absorbance is said to be directly proportional to concentration of a particular sample it is expressed as Aά1(1.3)(1.3)Aά1.  Though the comparison of the blank cuvette with a sample is the most common method used in beer’s law calculation, you can also draw a graph using the normal solutions to decide a concentration of a particular specimen. The proportion of light absorbed depends on how many molecules it interacts with. The absorbance of the solution varies as the concentration or size of the container varies.  The values of the molar absorptivity in beer’s law vary hugely. Beer’s law is limited by both chemical and instrumental factors, which include a scattering of lights, the fluorescence of the sample, the change in the refractive index at the high analyte concentration, stray lights, shift in the chemical equilibria and non-monochromatic radiation. 

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