Abstract: An apparatus for the analysis of a sample by means of an infrared (IR) spectroscopy, comprising a vessel (1) rotating during operation for holding the sample, a measuring head (2, 2?) connected with the vessel, a spectrometer (8) which is supplied with IR radiation reflected by the sample, and at least one first optical fiber element (4a) for transmitting the IR radiation reflected by the sample, is characterized in that the spectrometer (8) is stationary and a first rotary feed through (7, 7?, 7a, 7a?) is provided for coupling the reflected IR radiation from the first optical fiber element (4a) into a second optical fiber element (4b), in which the first optical fiber element (4a) is connected with the rotating part of the first rotary feed through (7, 7?, 7a, 7a?) and the spectrometer (8) is connected with the stationary part of the first rotary feed through (7, 7?, 7a, 7a?) via the second optical fiber element (4b).