Oil is usually a composite blend of many different types of hydrocarbon molecules.
Fluorescence as a detection method makes use of the fact that some of those molecules, when excited, will emit light at a specific wavelength.
A light source is directed into the water stream (containing the oil). Hydrocarbons are excited by the absorption of light and subsequently relax to a lower energy state before returning to ground state by emitting fluorescent light.
The intensity of the fluorescent light emitted is proportional to the total oil concentration.
Oil in Water Analysis with Laser Induced Fluorescence
In a Laser Induced Fluorescence (LIF) approach a laser is employed as the excitation source. The laser provides a more spectrally intense and selective excitation with a more defined and narrower spectral background level. The laser spectroscopy capability can be tailored with the application to provide enhanced accuracy and repeatability in the detection of oil in water.