25ppm H2S/50-300ppm CO/2.5%CH4/10-20%O2/N2

[labcal]

Hi, Everyone,

I am newer on GC, I am looking for a method to test above mixture on GC, I have CP-3800 with FID, TCD coming with 2 packed columns. I can just test CH4 and O2. there is not enough sensitivity for H2S and CO.
Can anyone help me? Thanks.

WJ

[chromatographer1]

To increase the sensitivity of your TCD's limit for H2S and CO you will be required to replace it with a Helium Ionization Detector. Otherwise you have to increase your sample size to 1mL to measure the 25 ppm level of H2S accurately. A manual syringe is unacceptable due to the lack of inertness required. A sampling valve with deactivated loop and a well deactivated column and support will be necessary to perform your analysis. If you choose to use a FPD you will have to make changes to your sample size to measure CO accurately as well as using a glass or fused silica lined column using your TCD.

You are welcome to email technical service at Supelco or call your local office if you require additional assistance.

best wishes,

Rodney George
Senior Research and Development Scientist
Gas Separations Research
Supelco
595 North Harrison Road
Bellefonte, PA 16823

814-359-5737 voice
814-359-5459 fax
rodney.george@sial.com

[AICMM]

labcal,

An HID will do all of the components you are interested in. If the TCD will do the CO and the others, the H2S is doable by argon mode PID or AID. I have a customer who has done sub-ppm levels of H2S using this mode of detection.

Best regards.

[labcal]

Hi, Rodney,

Thank you so much for your help.
I want make sure what you mean using a glass or fused silica lined column will help TCD to test CO. is right?
Thanks again.

WJ

[labcal]

Hi, AICMM,

Thank you. Do you think that the TCD can test this level CO?

best wish

WJ

[chromatographer1]

At 50 ppm CO using bare steel you may suffer non-reproducible losses of CO each time you inject. They may not be significant, but they might.

It is better to use glass lined SS or fused silica lined SS or just glass columns for trace O2 and CO analysis.

For example I have seen a 10 ft SS column adsorb 100 ppm of O2, and significant amounts of other organic molecules.

I hope this is helpful,

best wishes,

Rod

[labcal]

HI, Rod

yes, that's very helpful. Thanks. How about sample loop? need special one?


WJ

[chromatographer1]

Assuming you have a 0.030" ID ports on your sampling valve, I would suggest fused silica lined SS loop 1mm ID 1/16"OD tubing.

Don't forget the sample system tubing. It also must be very inert. Losing the H2S on the way to the valve is not helpful.

May you have success in your endeavor.

best wishes,

Rod

[labcal]

Hi, Rod,

Thanks a lot.

WJ