Chromatography Forum

Hello everybody,

I am using the disposable circular chips (4mm dia) of PDMS for the sorption studies. Presently, I extract these chips ultrasonically with hexane. In doing so, i have to compromise on recovery, time and some siloxane oligomers. We dont have any thermal desorber. I am just wondering how can i directly desorb these chips in the glass liner. We have a split/splitless inlet. Previously, I tried to use the chip in inlet but I saw siloxane peaks.

Does anyone of you have any advice/experience on this? I will appreciate your help in this connection.

Essentially what you are proposing is equivalent to SPME or stir bar SPE with a siloxane fiber, but with a much larger volume of silicone rubber. I would guess also that the silicone that you are using is not designed for high temperatures.

Whenever and however you use silicones you will get siloxane peaks, and they are likely to be worse at high temperatures, so if your aim with the thermal desorption is to reduce siloxane interference, then I do not think that it will help, and it will probably make it worse.

Peter

Unless is some highly crosslinked PDMS you will always see siloxanes peaks at T > 150C (without air).
Manual thermal desorption of a large PDMS chip is going to be difficult without a cryotrap.

Maybe you can try another solvent for your extraction? Acetonitrile/methanol mixture generally works for me. THF might be an option too if these pdms chips are single use.

Good luck.
bhuvfe