Chromatography Forum

I have two Varian CP3800 GCs outfitted with 3 different detectors,TCDs, FID and PDHID. I run analyses of gas samples collected at volcanoes and geothermal systems.
I have problems with stability for SO2 analyses when using the TCD (Helium carrier gas, Poropaq Q column). Instead I've been running those samples on the PDHID (ShinCarbon column) as the stability is better (but not great).

I spend a lot of time with calibration and double checking for the SO2 analyses and I am looking for a better column. SO2 seems to sorb onto the column especially at low concentrations.

I recently asked Restek for advice on a column for SO2, they suggested a Hayesep A, packed column. I just installed that and am running a few tests but it appears to have the same problem with SO2 loss at low concentrations.

I would like to find an alternative column if there is such thing. Any advice is appreciated.

Deb

Hi , SO2 is a very reactive gas and it is possible that it is absorbed by the different sample injection lines, such as the valve and injection loop, indeed the TCD detector is not highly recommended to detect this type of gas, the PDHID is better. reason sulfur is so difficult to measure is that it disappears on contact with hot stainless steel surfaces; of course FPD is the bets.
even limited contact with a hot stainless steel sample loop will destroy any sulfur in the gas sample, try using silco steel or teflon sample lines and loops , good luck

Thank you, the PDHID has worked, but calibration doesn't hold from day to day. It almost sounds like we need a dedicated GC for SO2 analysis.

hi, that would be a good idea

Did you fix the problem? We might have a better solution

Thank you, the PDHID has worked, but calibration doesn't hold from day to day. It almost sounds like we need a dedicated GC for SO2 analysis.

We tried a Restek silco-steel Hayesep column on a TCD and that did not work. We returned to our former method using the PDHID with a ShinCarbon column, but we are searching for a better solution.
Thanks Deb

i don't know how to attach pic or files. if you are interested, contact me at mike_t@gs-tek.com

thanks, will do

i don't know how to attach pic or files. if you are interested, contact me at mike_t@gs-tek.com

I didn't see a way to send a private message, but you should let whoever is in charge of your website know it needs some work. Lots of images with broken links, hyperlinks that just go to 404 screens, etc.

have you considered a U-bond. I have had very good luck with RT-U-Bond from Restek.

Best regards,

I have not heard of the term U-bond before. When I first started working on this issue I contacted Reztek and they recommended the silco steel column, which did not work.
thanks

REstek part number 19750 - as an example. "Normal" bond column, not metal. I would be leary of metal in this application.
Best regards,