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General considerations and theoretical background Laws of fluorescence spectrophotometry

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  413

2026-11-10

35

General considerations and theoretical background

Laws of fluorescence spectrophotometry

The power of fluorescent radiation If is proportional to the radiant power of the excitation beam absorbed by the system:

The constant K depends upon the quantum efficiency of the fluorescence. To relate I_f to the molar concentration c of the fluorescing molecule, Beer’s law can be used:

By substituting Equation (15.20) into (15.19) we obtain:

After expansion of the exponential term, and provided ɛlc<0.05, we can write:

or at constant I₀:

Thus, a plot of the fluorescence power of a solution versus the concentration of the emitting species should be linear at low concentrations. Limiting factors for linearity are not only the concentration of the solute, but also factors such as the blank fluorescence, quenching and absorption of exciting radiation by the solvent.