Rubber/PTFE vs. Silicone/PTFE vial septa

Discussions about sample preparation: extraction, cleanup, derivatization, etc.

4 posts Page 1 of 1
Hi all.

Can anyone please explain the difference between PTFE/rubber and PTFE/silicone vial septa? Rubber is substantially cheaper than silicone but I'm not familiar with the differences between the two.

Any help is appreciated.
It depends on your analysis. If you are using a 'very' non-polar solvent, components from rubber may leach out and give you 'strange' peaks in your chromatogram. Contamination will always a concern.

If you are using a polar solvent like water, this will not be a concern.

PTFE is a form of Teflon.
Hi

To expand on HPLC chemist's reply

As far as I am aware and to answer your query

The septa are formed from 2 layers
The PTFE is on the lower side that faces your sample in the vial and is relatively inert to solvents

The top side is red coloured rubber or a silicone that helps to make the seal with the cap on crimping.

In general the Rubber/PTFE septum is fine for general use for 1 or 2 injections within a short space of time

Bear in mind HPLC chemist's reply - with a Rubber/PTFE septum - if left for a while after piercing , both polar and non polar solvents can leach out unwanted contaminants from the rubber

Silicone/PTFE septa will suffer less from this

There is unlikely to be any significant cost difference

Does that help?

Regards

Ralph
If you are talking about headspace vial septa you will find that the rubber ones tend to grip the sampling needle, making the septum more difficult to penetrate. This is not a problem with valve and loop samples that have short, strong needles but it can bend needles on syringes.

Peter
Peter Apps
4 posts Page 1 of 1

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