Detection device for quantitative detection of predetermined molecules, in particular medium size protein molecules, in a sample liquid with a light source for emitting measurement radiation, a section for irradiating the sample liquid and a light detector for measuring the detection radiation exiting the section for irradiating the sample liquid, as well as an analysis stage located downstream of the light detector for analyzing the detector signal, wherein the light source is designed such that the measurement radiation has a spectral range exciting the intrinsic fluorescence of a molecule to be determined, and the light detector is designed such that at least one spectral range of the detection radiation is measured, in which the molecule emits intrinsic fluorescence radiation.
