The Fluorescence spectrum represents the light emitted from a sample, after the excitation at a different wavelength (usually in UV). In general the fluorescence light has low intensity, so the measurement requires a) the direction of the excitation light to be perpendicular to the light that is measured (fluorescence), or/and the use of a filter, for better isolation of the two spectra, and b) a high sensitivity spectrometer.

The sample under investigation can be either solid or liquid. Figure 1 shows a general Fluorescence set-up for liquids implemented with a FR-tool. For detailed description of the absorbance measurement procedure, please refer to the related section on FR-Monitor manual, in Download section.