Choosing the right septum depends on both your system and your application. Almost all septa are coated with an inert material on the side facing the sample. The sample is thus protected by a possible contamination with the carrier material. The carrier materials themselves have different properties in terms of purity, hardness, thickness and reclosure properties.
The most common septa consist of:
Likewise, cross-slit septa can prevent the formation of a vacuum in the bottle. Suitable for thin, sensitive injection needles, but with poorer reclosure properties. Therefore, more suitable for one-time injections. Temperature resistant from -60 ° C to 200 ° C.
For dull, thick or particularly sensitive needles, the septa are also available pre-slit. For particularly sensitive analyzes, PTFE-coated silicone septa can also be used on both sides. Other septums are also available for headspace analysis: Butyl / PTFE pharmaceutical fix, where only the butyl areas that come into contact with the sample are coated with PTFE to ensure a particularly good seal and silicone / aluminum septa.