TCD Operation

[cmoral]

Hi all,

I am trying to get a TCD working with a 5890 series II GC but I haven't used a TCD in a long time and am not sure how to go about setting it up. I want to
be able to monitor NO, N2, and O2. Could someone out there just give me some tips on where to start...i.e. what gas (used helium before I think), what oven temperatures...etc.

Also, the TCD has not been operating since 1999 but I have turned on the GC and hear it ticking. I have tried injecting just air samples to see if I get any peaks but nothing but a big blob. I have to check the column but I think it is the right one for this application.

The other option is to use the ECD - can that detect N2O, NO2, and NO?

Any help would be appreciated.

[chromatographer1]

No column info.

No flow or type of carrier info.

No info on amount of air injected.

Do you really want help?

Please, really, give some details about what you are doing and how.

The more you don't tell us, the more we can't tell you.

Yes, the Agilent TCD ticks when working.

Temperature limit is 150°C to ???, but 150°C is fine for gas work.

Good luck,

Rod

[cmoral]

Sorry, Rod, about the lack of detail.

I will get all the info I can and then ask again for some help. I just wasn't really sure where to start with respect to flow and gases.

[chromatographer1]

Please come back when you have some info.

The place to start: is to get as much information as possible and THEN share it and ask for assistance.

Good luck,

Rod

[AICMM]

cmoral,

The ticking is normal on the HP/Agilent TCD. The blob suggests column issues rather than detector but without more info really hard to say. Make sure you do not turn the detector on unless you have had flow through the TCD for a while (another use for a flow meter!) and make sure you do not turn the flow off until after you have turned the filament off.

Best regards,

AICMM

[cmoral]

Hi,

I have some info on the TCD operations, column head pressure at 20, column flow was about 5, make-up about 5, ref 20, all helium, split/splitless flow at 192, septum purge at 5,

I have a Restek Q-Plot column in the GC. Was able to get a nice nitrogen peak to come out. Baseline signal was around 10 but was starting to drop a bit. So I think the TCD is working but probably not optimized yet and we still have to try to get signals for NO and NO2.

If you have suggestions for optimizing the TCD flows, that would be great. One thing, though, our output pressure on our He tank is 25 PSI. To get a higher flow rate on the column, make-up, and ref, should I increase the output pressure because the knobs for make-up and ref are wide open and not a lot is coming out of the column end (i.e. should be at least 15 ml/min, I think).

Suggestions would be much appreciated.

[chromatographer1]

Increase your tank output pressure to 40 psi, perhaps more.

Your capillary is .32mm or .53mm ID ?

5 is fine for .32mm ID.

Adjust the column temperature, the split ratio (now about 40:1), and maybe the column flow to optimize your separations.

Let us know how it all works out.

best wishes,

Rod

I would still prefer a micropacked column............ especially for low levels

[cmoral]

Hi Rod,

I think the ID is 0.53 but not positive. Will have to check. I will increase the tank output pressure to 40 or so. When you say change the column temp, split ratio, and column flow, do you have any suggestions? The oven temperature program is running at 35 oC for 4 minutes. Nitrogen is coming out at about 3.5 min.

I'll look into a micropacked column but we have limited resources so might be stuck with what we have.

Thanks.

[chromatographer1]

Start at 27°C and run isothermal until CO2 elutes. You may have to put a bowl of ice in the oven to reach that temp.

Then try 30°C 33°C 36°C 38°C 42°C 45°C 48°C.................. well you get the idea.

Repeat for each column flow rate you choose.

Start at 5, then 7.5 then 10, then 12.5 cc/min........... you get the idea.

air has about 400 ppm CO2

Good luck,

Rod

[cmoral]

Thanks Rod. I'll give everything you suggest a try.

Will let you know how things turn out.

I really appreciate your help.

[cmoral]

Hi Rod,

I noted that you had replied to a previous sender the following reply re: analysis of NO, N2O, and NO2.

"Why would you want to use anything but Porapak P or Q to do this?

Both separate NO and NO2 from N20 and both put the two peaks ahead of N2O.

I would use a P followed by a Q."

Since this seems to be exactly what I need, I think the better column to use would be the Porapak P or Q instead of the RT-QPlot. Why have you said that you would use P then Q. Should I be using two columns for the separation?

Also, can the analysis be done at 25oC or higher, with a TCD or ECD?

Looks like I am narrowing in on the right technique.

CMoral