Properties and applications of septa made of TEF, PTFE, butyl, silicone etc.

Naturkautschuk /TEF |
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Application: |
HPLC/GC |
• Standard quality for HPLC • Good reclosure properties for multiple injections • Relatively inexpensive • Temperature resistant from -40 ° C to 120 ° C • Not very clean as a natural product • Punching discs (punched from sheet / roll material
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RedRubber / PTFE (synthetic rubber) |
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Application: |
HPLC/GC |
• NEW standard quality for HPLC and GC • Synthetic rubber, cleaner and softer than natural rubber • Relatively inexpensive • Temperature resistant from -40 ° C to 110 ° C • Punching discs (punched from sheet / roll material)
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Butyl (septa / stopper) |
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Application: |
Headspace |
• In the absence of a PTFE coating, only for uncritical analyzes • Butyl as a synthetic rubber cleaner than natural rubber • Very cheap as there is no PTFE coating • Application examples: breweries, blood alcohol analyzes • Original Butyl stopper for PerkinElmer • Forming discs (vulcanized and formed in a mold)
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Pharma-Fix Septum Butyl / PTFE |
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Application: |
GC/HPLC/Headspace |
• Specialty: Pharma-Fix washer only centric PTFE-coated butyl disc; The elastic butyl lying on the glass edge achieves a significantly better seal than the slippery surface of a completely laminated sealing disc • Butyl as a synthetic rubber cleaner than natural rubber • Relatively inexpensive compared to silicone • Temperature resistant from -40 ° C to 120 ° C • Synthetic rubber has poorer reclosure properties than natural rubber • Forming discs (vulcanized and formed in a mold)
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(PTFE /) silicone / PTFE |
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Application: |
GC/HPLC/Headspace |
• Silicone is the purest synthetic elastomer and is therefore used for critical analyzes • Temperature resistant from -60 ° C to 200 ° C • Improved reclosure properties than NK / TEF as a synthetic elastomer • (segmented) septa in HPLC as penetration aids for thick / blunt needles and for producing a valve effect in the case of multiple injections • Specialty: PTFE-coated silicone washers on both sides for low particle formation • punching discs (punched from sheet / roll material)
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Silicon / aluminum foil |
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Application: |
Headspace |
• All chemical and physical properties, such as silicone / PTFE • However, slightly higher temperature resistance from -60 ° C to 220 ° C • Frequently on PerkinElmer devices • More expensive than PTFE-coated septa
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Pure PTFE septa |
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Application: |
HPLC |
• Very inert, therefore also as a coating on most other sealing discs • No elastomer -> No sealing -> No reclosing properties • Do not press-fit into caps; Are therefore often only sold unassembled • Very cheap • Only for very uncritical applications • Are often used on VWR (Merck) / Hitachi and Waters instruments
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Durometer (hardness of the septum)
Durometer is the hardness of a septum, expressed in ° shore. The higher the "shore" number, the harder the septum, the lower the "shore" number, the softer the septum. The softest sealing disc is 45 ° shore A and the hardest 70 ° shore A is hard. In addition to the thickness of the disc, the hardness is an important indicator, which septum is suitable for the penetration of a certain needles (sensitive needles, thin or thick needles, pointed or blunt needles, etc.).