There are situations where Beer-Lambert Law might not hold true. These deviations are either:
a) Chemical Deviations:
I. Association or dissociation:
At high concentrations, molecules may associate or dissociate, altering the species in solution and hence the absorption.
II. Reactions between solute and solvent:
A chemical reaction between the solute and solvent can change the nature of the absorbing species.
b) Instrumental Deviations:
II. Stray light:
Light outside the selected bandwidth entering the detector can cause a higher-than-expected absorbance reading.
II. Polychromatic radiation:
If the incident light isn't monochromatic, there can be errors, especially if the sample has a sharp absorbance peak.
c) Physical Deviations:
I. High concentrations:
At very high concentrations, the refractive index of the solution can change, affecting absorption.
II. Temperature and solvent effects:
Changing the solvent or temperature can affect the peak shape and position.
III. Scattering of light:
Particles or droplets in the sample can scatter light, affecting absorbance readings.
