Define the Beer's Law - Nutritional Biochemistry?
Beer's law states that the concentration of a substance is directly proportional to the amount of light absorbed or inversely proportional to the logarithm of the transmitted light.
Mathematically, Beer's law is expressed as
A = abc
Where,
A = Absorbance
a = Proportionality constant defined as absorptivity
b = Light path in centimeters
c = Concentration of the absorbing compound, usually expressed in grams per liter
This equation forms the basis of quantitative analysis by absorption photometry.
Absorbance values have no units; hence, the units for a are the reciprocal of those for b and c. When b is 1 cm and c is expressed in moles per liter, the symbol ∈ (epsilon) is substituted for the constant a. The value for ∈ is a constant for a given compound at a given wavelength under prescribed conditions of solvent, temperature, pH, etc., and is called the molar absorptivity. Values for ∈ are useful to characterize compounds, establish their purity, and compare sensitivities of measurements obtained on derivatives.