The aim of this work was the detection of surface adsorbates on technically employed solid-phase-catalysts of heterogeneously catalysed partial oxidations of alpha, beta-unsaturated aldehydes to the corresponding acids. Therefore, diffuse-reflectance-infrared-fourier-transformation-spectroscopy (drift-spectroscopy) was used. As a consequence of generally present problems (superposition of gas-phase- and adsorbate-absorption), measurements could not be carried out in commercially available measuring-cells. Within the scope of this work it was possible to develop a new measuring-cell that allows to detect adsorbates exclusively. As a new feature, the catalyst specimen as well as the reference-substance are placed in the same sample compartment and with that are exposed to the identical gas-atmosphere. Both, the catalyst as well as the reference-substance are placed in two sample cups inside of the reaction chamber on a revolvable gear wheel. With that, it is possible to switch between these two sample cups which can be introduced alternately into the IR-beam of the spectrometer. The scope of applications of this measurement cell covers investigations of structures of adsorbates and also changes of catalysts and solids respectively. Moreover, it can be used in the determination of the specific quantities of adsorbates and degrees of reduction of the catalyst. And finally it can be introduced as a “window into the reactor”. With the help of the new measuring cell partial oxidations of unsaturated aldehydes to the corresponding acids were examined as model reactions at two different catalyst-systems. Substantially, the adsorbates described in the literature, investigated in transmission modes and the deduced mechanisms for selective oxidation of C3-aldehydes to their corresponding acids could be confirmed. In addition it could be shown that the conversion of a C4-aldehyde follows the same mechanism.