Chromatography Forum

Hi There,

I really need someone help me on the detection of ammonia and Trimethylamina from the headspace of a chemical solution.

I have Agilent FID 6890N. The gases needs to be detected is a mixture of amonia and trimethylammonia released from the headspace of a chemical solution. The concentration could be as low as several ppm. but it caused customer's complaints.

Would someone be able to tell me what is the best way to the GC analysis on this misture? I am planing to use water to absorb the gas first and then do the GC analysis. But my questions are:
1. what test condition I should set for the NH3, N(Ch3)3 mixture? what kind of column I should use? what is the inlet temp, detector inlet temp? column temp? floe rate and split ratio, etc. currently, I am using helium as carrier gas and H2 as the flame gas.
2. Would NH3 be separated from N(NH3)3 ?
3. How to prepare the stardards?

Thanks a lot in advance,

Julia

Why not do headspace SPME and use the spme fiber for injection?

Julia,

I could hardly believe your post. You are asking a GREAT deal for free. WOW is my first response.

Now, I can tell you what you should NOT do.

Try not to trap the ammonia and Trimethyl ammonia (your formula does not match the name) in water but keep it in vapor if possible.

Don't use any fused silica or silicone phase column (possible exception is a CAM capillary).

A Chromosorb 103 or a Hayesep C column may be necessary. (Don't use glass or ordinary metal tubing for the column, however.) Apiezon L with 2% KOH might be a useful phase, or perhaps a base deactivated Carbopack B.

You should be using base deactivated metal parts in your headspace analyzer. You hopefully know how to prepare such parts. They are usually not available for order, but must be custom made.

You may wish to use a Photoionization detector, but a Helium ionization detector should work ok.

Good luck in your research and please share your findings.

best wishes,

Rod

Julia,

You really should be using wet chemistry to do your analysis. Using a water trap would then be a good idea. OR you could perform ion chromatography using your water trap.

Good luck,

Rod

Hi Julia

With an FID you are trying to do the impossible - it has no response useful response to ammonia.

Peter

Why not do headspace SPME and use the spme fiber for injection?

I don't know what is SPME. Is it a type of sryringe. You mean dicrect withdraw headspace gas and inject it into GC?

Thanks,

Julia

Julia,

I could hardly believe your post. You are asking a GREAT deal for free. WOW is my first response.

Now, I can tell you what you should NOT do.

Try not to trap the ammonia and Trimethyl ammonia (your formula does not match the name) in water but keep it in vapor if possible.

Don't use any fused silica or silicone phase column (possible exception is a CAM capillary).

A Chromosorb 103 or a Hayesep C column may be necessary. (Don't use glass or ordinary metal tubing for the column, however.) Apiezon L with 2% KOH might be a useful phase, or perhaps a base deactivated Carbopack B.

You should be using base deactivated metal parts in your headspace analyzer. You hopefully know how to prepare such parts. They are usually not available for order, but must be custom made.

You may wish to use a Photoionization detector, but a Helium ionization detector should work ok.

Good luck in your research and please share your findings.

best wishes,

Rod

Thank you Rod,

The column you suggested ate compatible with GC-FID 6890N? Do you have any suggestion of how to make them or where can them?

Thanks for the help..
Julia

Hi Julia

With an FID you are trying to do the impossible - it has no response useful response to ammonia.

Peter

Peter, Your answer agrees on the opinion from Agilent. Thanks.

Julia

Metal columns can be made to work with your GC.

BUT
I don't know where you can base deactivated metal tubing. I used to make it myself, but it is a proprietary technique and I cannot share it with you.

I can only suggest a bonded OV-225 or OV-17 might be a suitable capillary column, or a base deactivated Carbowax capillary.

A PID or HID should be avilable from Agilent or AIC or Valco.

Good luck.

Rod

Metal columns can be made to work with your GC.

BUT
I don't know where you can base deactivated metal tubing. I used to make it myself, but it is a proprietary technique and I cannot share it with you.

I can only suggest a bonded OV-225 or OV-17 might be a suitable capillary column, or a base deactivated Carbowax capillary.

A PID or HID should be avilable from Agilent or AIC or Valco.

Good luck.

Rod

Thanks alot for shearing your experices with me.

Happy Christmas!

Julia