Chromatography Forum

Hi,

I need help for the HP5890 II TCD signal.

When I turn on both detectors, only FID detector signal has an increase and then stabilize. TCD detector signal doesn't change the position, just change from straight line to baseline noise. Also, when I changed the TCD detector temperature, there is no any change for the signal. Could you please help me on that?

Is it normal the baseline position doesn't change when the TCD detector turn on (The baseline just turn from straight line to noise)?

Thanks!

What is the plot scale? Is any of the data being truncated (if it goes negative for example)?

What is your carrier gas, column type, make-up flow, reference flow, column flow, and (critically) detector temperature? depending on all those factors, a normal baseline could be anywhere from 5 to 50mV.

It is not normal for the baseline to not move at all, but it could move a very small amount that isn't visible because of the plot scale.

Regards,
Aidan

Hi Aidan,

Thanks so much for your response.
The baseline doesn't change at all, the scale is small enough. When I turn the TCD on, is it usually the signal will increase and then decrease and then stabilize? The FID signal is like that.

Thanks!

Is this a new problem? Did it used to work okay? Can you hear the TCD clicking to itself?

This is an old GC, I bought from other company. It's my first time to start using the GC, the baseline just like that. I can here the clicking, does that mean the TCD detector works? If there is baseline noise, can I assume the TCD detector is not broken?

Thanks so much!

Hi again,
If you answer the questions I asked before it may help.

Yes, the TCD baseline normally increases decreases and stabilizes after being turned on, and definitely should be non-zero.

One other thing to check: What is the signal zero set at currently? On the GC press "SIG 1" (or 2 depending on which one is the TCD). If the display shows a letter (e.g. A or B) then press "SIG 1" (or 2) again. It should display a raw value for the signal, verify it is or is not zero. Next press "ZERO". If there is a number other than 0, type 0 and press "ENTER". Now check the raw signal value again.

Good luck!

When I turn off the TCD detector, the signal position is "0" on y axis, when I turn on the TCD detector, the position doesn't change but the noise appear. I can also hear the TCD clicking. I pressed SIG 1 twice and the value is 0 and then I pressed ENTER.

The TCD detector temperature is 250 C and the carrier gas is Ar. The column add make up gas flow is 10 ml/min and the column add make up add reference gas is 60 ml/min. The plot scale is small enough but there still no any position change for the signal. The column I used is ShinCarbon micropacked column from Restek company, the item number is 19043.

Thanks so much for helping me!