Chromatography Forum

My professor has charged me with finding a way to detect/quantitate hydrogen in the head space of some of our photocatalytic systems. One of the groups at our university has a Varian 450 GC that no one in their group knows how to use so i've spent the last week learning the system. Yesterday I finally was able to analyze a standard N2/H2 mixture but found out that there is absolutely no separation of the gases. I also tried shooting air through the system jst to test that and of course no separation.

Digging around in the archives I found a post talking about different columns and looked up a few on Sigma-Aldrich that would work I believe.
Carboxen 1010 PLOT and the Mol Sieve 5A PLOT seemed to be what I was looking for.

So after all that down to my question. Are these compatible with the Varian 450 GC or does someone have any suggestions for different columns that would work better?

Also would it be possible to install them by myself or would I need a service person to come do it?

Thanks in advance for any advice!
Allen

If you can use packed columns then buy a packed column.

If you can use capillary columns then buy capillary columns.

Your GC is set up to use one or the other, or even perhaps both types of columns.

If you are sampling headspace containing water and other possible volatile organics, then I would use a Carboxen column, either capillary or packed.

You need to answer some questions about your machine so I would suggest you make a free call to a vendor and they will advise you.

Customer service information is given at no cost to you.

Take advantage of a good thing.

IF YOU have to ask about how to install a column perhaps you should get someone who knows how. Maybe the professor or a grad student.

best wishes,

ROD

Thanks for the reply. What i have been seeing is that people typically use argon as a carrier gas instead of Helium due to the similar conductivity of hydrogen and helium. Only problem s I can't figure out how to switch up the carrier gas on the GC without switching the lines. Any suggestions? Ive looked through the user manual of the GC and Galaxie but can't foind anything

Do you have argon available?

If it is in tanks, then you need a regulator and suitable supply lines with shutoff valves.

You also need a valve to change the source of carrier gas that will be hooked up to both gas supplies and to the GC.

Your gas supplier can furnish these or you can go to vendor of such articles like Alltech, Restek, or Supelco.

You may wish to add traps for moisture or hydrocarbons.

Call a vendor for technical assistance. Again it is free and educational.

best wishes,

Rod

Well, to change the carrier gas, you have to run a different gas line to that connection on the GC.

You also need to change the carrier gas type in Galaxie, for our 430 this is a PITA and a bit like starting up Apollo 13. If you need to then I can put it up here, I havne't used a 450 but I am guessing it is the same or close enough. That said, some of them will auto-detect the carrier gas when starting up the instrument (I am told), so it may be just a case of letting it flush through with argon for 5-10min and then restarting the GC.

If you could let me know how to change the carrier gas type in galaxy that would be great. I'm gonna give it a shot this afternoon and hopefully start getting some separation of my gases. There is argon, helium, hydrogen, and compressed air running to the gc all at once so I assumed that the carrier gas could be switched between all of them. I realize now that each detector has it's own specific gas; ECD has the argon, TCD has helium, and the flame uses hydrogen and compressed air.

I suspect your 'argon' detector gas may actually be argon/methane 90/10 or 95/05.

Such are commonly used for an ECD using helium as the carrier gas for the column.

best wishes,

Rod

For measuring H2, they often use argon because there is a non-linearity in he/H2 mixtures. That can give you very strange peak shapes for H2.

H2 will elute as the first peak from carbon type columns. Even better would be to use molsieve 5A.
You can get this material also packed into 0.53mm metal (MXT)columns. Such column you can use also with splitted injection systems and are pretty economical.

all depend on matrix you put on there. if water is present, carbon may be preferred as water can be baked of at 200C and retention times are not affected too much.. Molsieve however will adsorb water strong and retention time will change in time. This material needs bake at 300C to remove water.

jaap de zeeuw, restek corporation

To change carrier gas on our Varian 430 using Galaxie...

On the GC panel, press the Setup key (icon of tools) and use the Enter key to advance to IEFC setup, select gas type. Use the up and down arrows to choose the right (new) gas. Press Enter again. Advance again until you see DEFC gas type and also change this to the new one. You can swap gas supplies over now, you might get errors as the new gas flushes through.

Open the Configurator, go to Systems, right-click on the GC and choose Edit. Skip through the wizard and press OK at the end. You'll be asked if you want to configure your system now, press Yes. Fidn teh button to upload or download instrument settings (the tab with the IP address), and upload the settings from the GC to the PC.

You should now be able to close the configurator and load a suitable method in the usual way. It seems that simply putting the new gases into the method and loading that doesn't change the settings in the GC, you have to do that manually as described above, unless it has auto detection (however that works).

Thanks a lot! I switched eveyrthing up (broke 2 ferruls in the process and had to order more) and started seeing separation in my gases until i got an error saying

"Error 45 Middle EFC pressure ready check timeout"

Any one got a quick fix? If I turn the middle column pressure down below 0.5 psi (normally at 10) then it will pas the ready check but my chromatographs slowly decrease in voltage (using an TCD) over the course of the entire experiment and can't detect anything. Any suggestions?

You almost certainly have a large leak - find and fix it and the EPC will be able to maintain inlet pressure.

Peter