We report Ambient pressure X-ray Photoelectron Spectroscopy Endstation with an integrated chemical analytical system that consists of a residual gas analyzer in the 2nd differential pumping stage and a new low-reactive sample holder heating assembly. This system has a linear response to the reaction chamber gas pressure. The sample heating assembly also has a low dark reaction rate up to 400 degrees C for H-2 and CO oxidation. We expect this chemical analytical system will expand our capabilities in conducting inoperando catalysis research. (C) 2012 Elsevier B.V. All rights reserved.