GC-TCD Packed Column Dilemma

[Mariquit]

I am working a GC-TCD in which I have two packed columns. One is poropak Q and one contains molecular sieve 5A. The gases that I want to identify are xylene/benzene/toluene, CO2, CO, O2. My carrier gas is Helium. I have a six way valve that takes care of sampling and injection.
I first saturate my helium gas with o-xylene by bubbling it through liquid xylene placed in a water bath. Then i inject the sample to verify the amount of xylene in my GC. The problem now is that I cannot seem to detect any peaks at all... I am suspecting that there might be better packing material (rather than poropak q) that can help me identify my xylene peak.. Is my hypothesis valid?

Please advise.

Another thing... is there a rule about the size, length, material of packed columns that we have to use?

[chromatographer1]

Did you burn out the filament in your hot wire TCD?

Perhaps your valve is not injecting?

To separate such a wide range of analytes you really need two different types of columns or subambient oven conditions with programming to temperatures above 100°C.

Many columns will separate BZ/Tol/Xy with separation of the fixed gases as a separate earlier eluting peak.

To separate O2 and CO2 you need a Mole Sieve (5A or 13X) or a Carbon Sieve (G or Carboxen 1000).

These don't separate the aromatics in a timely manner.

No peaks means no flow, no sample injected, or your detector is broken.

Good luck in finding the fault.

best wishes,

Rod, the short timer (two more days)

[Mariquit]

Thanks for the reply, Short timer Rod.

I am sorry to confuse you. My TCD can detect peaks except for the xylene. It can detect O2 and N2, which by the way is also my concern, i am suspecting there is a leak somewhere because I can still detect air even after hours of purging with He.

maybe I'll try to clean my column poropak q...

If for example I am to replace the packed column, how much packing materials and how long would the packed column be?

Help!

[Ron]

I noticed that you are saturating the carrier gas with xylene, then you don't see a response for xylene. If the carrier is truly saturated with xylene, the xylene signal should be constant, and you would not see a xylene signal when you injected more xylene.