An apparatus has been devised, utilizing the principle of cyclic enrichment, by means of which many gases and vapors diluted with an inert gas can be subjected to various reactions, concentrated, and transferred to the gas-liquid chromatograph with negligible loss or contamination. With this device a reasonable approximation to plug flow into the chromatograph is obtained. The entire sample or any portion represented by a set of chromatographic peaks can be recollected at the chromatograph exit, treated chemically, reconcentrated, and then reanalyzed by GLC numerous times using different liquid phase columns, carrier gas flow rates, detectors, column oven temperatures, etc. Utilizing this apparatus, i t is shown that powdered metals and other additives do affect the pyrolysis of powdered polyvinylidene fluoride at 450' C.