Selection of the correct sample septum

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 re-closure properties.

The most common septa consist of:

• Natural rubber/TEF: Ideal for multiple injections due to the good re-closure properties. Temperature resistant from -40 ° C to 120 ° C
• Butyl/PTFE: Synthetic rubber with very good chemical properties. Temperature resistant from -40 ° C to 120 ° C
• Red Rubber/PTFE: Easier penetration than natural rubber/TFE and Butyl/PTFE, less particle formation. Temperature resistant from -40 ° C to 110 ° C.
• Silicone/PTFE: More pure than natural rubber, red rubber or butyl. Cross-slit septa are available as penetration aids and for lower particle formation.

Likewise, cross-slit septa can prevent the formation of a vacuum in the bottle. Suitable for thin, sensitive injection needles, but with poorer re-closure 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 analyses, PTFE-coated silicone septa can also be used on both sides. Other septa 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/aluminium septa.