a process and apparatus for testing material libraries , in particular catalysts , by means of coupled use of at least two analytical methods , preferably ir thermography and mass spectrometry . owing to the selected arrangement , the disadvantages of the two previously known individual methods are compensated for : the subsequent selectivity determination for selected sections by means of mass spectrometry invalidates the argument against ir thermography , of only being able to determine activities ; the rapid integrated determination of potentially “ good ” materials via ir thermography prevents an excessive loss of time by needing to test all materials of a library successively with the mass spectrometer . the reactor design permits , firstly , the integral recording of the entire reactor through a window which is transparent for the corresponding method and , secondly , permits the simultaneous , automated application of a second analytical method to selected materials of a material library , which have been rated as active by the optical method . in the case described , the optical method provides information on the material activity for a set problem , and the second analytical method determines the selectivity of the materials .