High quality silicone septa. Total control over every step of the manufacturing process is carefully maintained, including extraction tests of each batch of material, to ensure extremely low extraction levels that could otherwise affect analytical results. The purpose of a septum in a GC system is to isolate the sample flow path from the outside world. The septum provides a barrier that is easily penetrated by the injector needle while maintaining internal pressure without causing any contamination to the system. An ideal septum has low bleed and long life.