This letter deals with the in-situ determination of important inorganic gas phase species in high temperature gasification product gas. The fuels are waste wood and German hard coal which were co-gasified at 1500 degrees C in lab-scale experiments. The release of the vapour species (H2S+)-H-34, (HCl+)-H-36, (KOH+)-K-56, (NaCl+)-Na-58, (COS+)-C-60, (SO2+)-S-64, and (KCl+)-K-74 was determined online by a Molecular Beam Mass Spectrometer. The experimentally determined data sets were compared to calculated data sets in order to distinguish the underlying release mechanisms. The release behaviour of the inorganics (H2S+)-H-34, (HCl+)-H-36, (COS+)-C-60, (SO2+)-S-64 and (NaCl+)-Na-58 cannot be attributed to simple mixing and dilution effect only. Further, it is shown that the release of these inorganics is significantly influenced by secondary reactions, e.g. competitive reaction with S and Cl. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.