A special flow-through vaporizor-pyrolyzer coupled with subambient GC column operation was developed for the characterization of the organic material present in an inorganic matrix. The sample is heated in stepwise fashion while compounds liberated from the matrix at that particular temperature are trapped on the GC column. When the source of heat is removed from the sample, the GC column is temperature programmed and the compounds eluted. Thus, it is possible to distinguish between compounds that are in their native form in the matrix and those that are produced by the thermal fragmentation of a larger organic molecule.