This is the unanswered question stored very long in my mind and till now I could not find a right answer. Google search educated me that the red surface is the PTFE material compatible to wider range of chemical compared to the white silicone surface. But which shall be inner surface facing the sample and which shall make the outer surface is the answer that I wanted to know from any of you coming across this.I am confused with this since I have came across different types of septa, with the red facing in, white facing out, the opposite and both sides made of the red PTFE.Can someone assist with this?
virtually all vial seals have two or more layers. The main body of the septum (thick layer) is a substrate to which the chemically resistant thin layer (usually PTFE) is bonded. The thin layer prevents the monomer from the thick layer leaching into your vial (and your sample). Which seal material(s) to use depends on what instrument you are using (LC-MS, GC-MS, ICP-MS...), what solvents/reagents you are using (catalogues often have chemical compatibility charts) and how well you want the septum to reseal when punctured (it's never 100%).
So thin side facing your sample, thick side facing up. For GC septa that transparent PTFE coating (shiny side faces your samples, matt side up).
Nathan has provided a detailed answer already, but my suggestion is to use the HPLC vial seals with Teflon surfaces. Septa are available with two or even three layers of material. PTFE/Silicone septa (T/S) are the most useful for HPLC applications as they have wide chemical compatibility and low extractables (I recommend them for general purpose use) . These area available in 2-layer forms (S/T) as well as three-layer versions (T/S/T). Also available are septa with combinations of natural and synthetic red rubber, PP & PE (single use only) and even Viton septa.
*Note: To make matters confusing, Teflon septa are available in red and white colors. On most of the HPLC septa, the white surface is the Teflon side, so face it towards the liquid sample, but check with the supplier you use as this varies a lot (e.g. Agilent sells both red and white Teflon septa) !
- BTW: To answer your original question; "Which vial septa the right one to be used for HPLC?". The answer is, the HPLC vial septa which are compatible with your specific application needs and meet the needed chemical, temperature and use requirements. Please consult your supplier for more information.
Dear Mr. William and Mr. Nathan,thanks a lot for your valuable input.
- Badges
- Science method