Abstract: The invention relates to a method and a device (1) for determining a concentration (c) of a fluorescent substance in a medium, wherein an excitation radiation having an excitation wavelength (?ex) is radiated through the medium having the fluorescent substance so that the fluorescent substance is excited in such a way that the fluorescent substance emits a fluorescence radiation having a fluorescence wavelength (?em), wherein the intensity of the fluorescence (Ifluor) is measured, from which the concentration (c) of the fluorescent substance in the medium is determined, wherein additionally the intensity (Itrans,ex) of a transmitted portion of the excitation radiation is measured, wherein the concentration (c) of the fluorescent substance is determined from the intensity of the transmitted portion of the excitation radiation (Itrans,ex) and the intensity of the fluorescence (Ifluor).

Abstract: The invention relates to a device (1) for photometrically or spectrometrically examining a liquid sample (2), comprising a cuvette (3, 3?), which can be arranged in the beam path between a radiation source (4) and a radiation detector (5) and which accommodates the liquid sample (2) to be examined, a radiolucent inlet section (6) for coupling in radiation (20) produced by means of the radiation source (4), which radiation interacts with a sample volume (8), and a radiolucent outlet section (7) for coupling out radiation (20?) intended to be detected in the radiation detector (5), wherein the inlet section (6) has an inlet surface (11) convexly curved in such a way and/or the outlet section (7) has an outlet surface (12, 12?) spherically convexly curved in such a way that the incident radiation (20, 20?) is focused in the manner of a converging lens.

Abstract: The invention relates to a device (1) for photometrically or spectrometrically examining a liquid sample (2), comprising a cuvette (3, 3?), which can be arranged in the beam path between a radiation source (4) and a radiation detector (5) and which accommodates the liquid sample (2) to be examined, a radiolucent inlet section (6) for coupling in radiation (20) produced by means of the radiation source (4), which radiation interacts with a sample volume (8), and a radiolucent outlet section (7) for coupling out radiation (20?) intended to be detected in the radiation detector (5), wherein the inlet section (6) has an inlet surface (11) convexly curved in such a way and/or the outlet section (7) has an outlet surface (12, 12?) spherically convexly curved in such a way that the incident radiation (20, 20?) is focused in the manner of a converging lens.