Patent ID: 8334522

Claim:
A method for the quantitative determination of a concentration of fluorophores of at least one substance in a sample, comprising: coupling in a constant portion of a reference light of a reference light wave length (λ r ) emitted by a reference light source by an optical element in a direction of a first receiving element, detecting a first measured value (E s2 ) corresponding to the portion of the reference light coupled in and incident on the first receiving element, irradiating the sample with the excitation light of an excitation wave length (λ ex ) emitted by an excitation light source, detecting a second measured value (E mes2 ) corresponding to a portion of a fluorescent light of an emission wave length (λ em ) emitted by the sample and incident on the first receiving element, determining a ratio (E mes2 /E s2 ) of the second measured value (E mes2 ) to the first measured value (E s2 ), and determining a number of the fluorophores in the substance of the sample within a detection zone taking the ratio (E mes2 /E s2 ) into account, wherein an optical path of the constant portion of the reference light between the optical element and the first receiving element is the same as an optical path of the fluorescent light between the sample and the first receiving element.