General description of FD

operating principle:

measures the wavelength and intensity of fluorescent light that is emitted by an analyte when it relaxes
from an excited electronic state back to its ground state

the excitation is accomplished by UV-visible light absorption

often used to detect polycyclic aromatic hydrocarbons (PAHs)

advantages:

very low detection limit (has a 'zero' background and is hence up to 1000 times more sensitive than UV-visible absorption, which has a background of 100% transmission)
high selectivity, because not every molecule that absorbs light also fluoresces
analyte is not destroyed

disadvantages:

lower 'limit of linearity' (LOL) than UV-visible absorption detection
due to self-absorption of fluorescent light at high analyte concentrations (i.e., emitted fluorescent light is absorbed by other analyte molecules and hence does not reach the detector).

Terminology