Abstract: A system and a method of the interaction and preservation of two or more reagents used in a chemical reaction is described, in which the reagents are put in contact one with another only when a buffer (A) carrying a sample to be treated with said reagents breaks a partition barrier (4, 14) placed between two containers belonging to a device comprising a first upper container (2, 12) and a second lower container (3, 13) of a test tube (1), the bottom wall of the first container (2, 12) forming said partition barrier (4, 14) able to be perforated by the buffer (A) carrying the sample to be treated.