No Peak From TCD Detector

[LUXIAOXIAO]

Everything is correct, I can hear the TCD clicking, the gas ratio is correct (reference 18ml/min, makeup plus column 6ml/min), temperature for TCD detector is 250 degree C. The carrier gas is Ar. The TCD detector doesn't broken. There is no any peak, could someone help me out? Thanks!

[kubowicz.tomasz]

Hello

1.Check if your software is collecting correct signal (check all parameters).
2.Check if your column is not broken (check if it is not cut somewhere on the metal cage)
3.Check if your injector is working properly (check syringe or sample loop).

Regards

Tomasz Kubowicz

[GasMan]

More details are needed. What column are you using and what is your actual analysis. What is your inlet. Are you using a valve to inject the sample. The fact that you mention the TCD is ticking suggests that it is an HP/Agilent GC, but which model, 5890,6890 or 7890?

Gasman

[LUXIAOXIAO]

The tried shincarbon column from restek (#19043) with diameter 0.53 mm and length 2m, there is no peak. So I changed to using retention gap (just an empty column), there still no peak. The GC is HP 5890II. I used sample loop to introduce the sample. The sample loop should be fine since I used it for FID detector. The gas sample I used are 2% volumn O2/ Ar. I also introduced air but there is no peak.

[aidnai]

LuXiaoXaio,

Have you checked the switches on the TCD detector PCB? There is a switch that must be set for Ar/N2 vs. He/H2. On my instrument it is the switch on the right side and should be set to the left for Ar. The switches are labeled on the PCB itself.

If that isn't the problem, I think you need to consider some more drastic measures such as swapping the detector PCB, moving it to the other signal/channel, replacing the TCD, etc. I have found good prices on 5890 parts at http://www.aoti.net/5890com/.

Good luck!

[GasMan]

What flow are you expecting through your column? Is the outlet of the TCD detector connected to the FID? With the column that you are using, 2m x 530 or retention gap, you will have a very low head pressure. It is possible that the pressure at the inlet to the TCD due to the reference flow is higher than your headpressure, resulting in no flow in your column. This is a situation that I have seen on some GC's. I suggest the following. Stop the flow in your column and leave the TCD gases running. Measure the flow. Now turn on your column pressure and check that there is an increase in flow at your TCD exit equivalent to your expected column flow. IF you do not get the expected flow, increase the column pressure until you get the correct column flow.

Gasman

[LUXIAOXIAO]

Hi Gasman and aidnai,

The TCD and FID are used for separated column and the gas go through the TCD just vent. The switch is to Ar. There is flow increase after I turn on the gas flow go through the TCD detector. I dont know what should I do next.

Thanks for your help!

[aidnai]

Hi again,
What is the resistance of the filament?
According to this doc http://www.chem.agilent.com/Library/Sup ... a16093.pdf it should be 10ohms cold and 11-13ohms hot. Look at the doc for instructions to measuring the filament resistance.
Aidan

[LUXIAOXIAO]

Hi aidnai,

Thanks for your help, I measured the resistance before, the resistance is about 11.

Could you please let me know what's the influence for the reference gas flow rate and column flow rate on peak? If the flow rate is not correct, there is no peak?

Thanks!

[aidnai]

Hi LuXiaoXiao,
Mostly the flow rates will influence the zero offset. As you were not seeing any offset at all, that does indicate a problem. Unfortunately, I've mentioned everything I can think of. Hope you can eventually solve it!

Aidan

[LUXIAOXIAO]

Hi aidnai,

What does zero offset mean? Thanks!