Abstract: A photometric absorption detector, in particular for the use in liquid chromatography is provided, in which a test cell is penetrated by the rays emitted by a light source and in which the absorption of certain wave length ranges of the light by the sample is recorded by means of a photodetector arrangement. Means for the spectroscopical dispersion of the light emerging from the test cell are provided, and the photodetector arrangement can be displaced within the spectrum. There may be two independently displaceable photodetectors, one of which may be set to a measuring wave length, while the other one may be set to a reference wave length.