Selectivity in petroleum chemistry generally means multi-compound product compositions, distributed over a wide range from, e. g. hydrocarbon gases up to vapors of high boiling substances - thus providing analytical problems. Temporal resolution is required for investigating unsteady regimes of reaction, as pertinent during self-organization of catalytic processes or phenomena of catalyst deactivation. It is also of interest in temperature programmed operation as for catalyst regeneration, pyrolysis of organic materials as oil shale and biomass or TPD of pollutants recovered on adsorbents. For temporal resolution instant ampoule sampling has been developed. Ampoule samples are taken from the (hot) gaseous product flow in pre-evacuated glass ampoules in less than 1 s and stored without compositional changes for later GC-analysis. High resolution gas chromatography has been developed, starting at -80 degrees C for the separation of light gases and ending at, e. g. 250 degrees C for separating high boiling compounds (e. g. vapors of hydrocarbons C20). In the article, initial selectivity changes in Fischer-Tropsch synthesis (referring to chain growth, chain branching and olefin reactions, as caused by self-organization of the FT-regime) and also thermal regeneration of a HZSM5 catalyst used for methanol conversion at low temperature (referring to reactivation by de-alkylation of bulky benzene derivates) are being presented. (C) 2011 Elsevier B. V. All rights reserved.