Septum for magnetic precision thread screw cap ND18, Ø = 17.5 mm, Silicone blue transparent/PTFE white, 45° shore A, 1.3 mm, pack of 1000, LABSOLUTE®, Art. No. 17 02 1417

The choice of the right septa depends on the application. Many septa are PTFE coated on one side. PTFE is highly resistant against many chemicals and forms an inert border between the sample and the base material of the septa.

The septa"s base material has various physical and chemical properties, like temperature resistance, resealability, cleanliness, hardness and thickness.

Natural rubber/TEF

• Temperature-resistant from -40 °C to 120 °C
• Excellent resealability properties
• Inexpensive for standard applications in the fields of GC and HPLC

RedRubber/PTFE

• Temperature-resistant from -30 °C to 110 °C
• Softer and therefore easier to penetrate than natural rubber
• Not as good resealability properties as natural rubber
• Higher chemical purity than natural rubber
• Inexpensive for standard applications in the fields of GC and HPLC

Butyl/PTFE

• Temperature-resistant from -40 °C to 120 °C
• Higher chemical purity than natural rubber and RedRubber

Silicone/PTFE

• Temperature-resistant from -60 °C to 200 °C
• More suitable for single-injection applications
• Much higher chemical purity than natural rubber and RedRubber
• Very low particle formation during penetration in case of double-sided PTFE coating
• Best for the thin and fragile needles of the autosampler
• Best for critical analysis (UltraClean quality)