Chromatography Forum

Hello,
The output on one of our GCs is around 589,000. It was running fine over the weekend. The only thing we did was our weekly gas flow checks on Monday and I noticed the high output. I took out the collector to inspect the spring and the signal was still high without anything touching the spring. Does anyone know if there is anything else I should check or do I most likely need my electrometer replaced ?

What model GC is this?

That sounds eerily similar to the number you see on HP 5890s if the electrometer is grounded, although on those instruments I think the number is in the million range.

Hello Ben,
Thanks for your response! It is the Agilent 7890 model.

Hello,
The output on one of our GCs is around 589,000. It was running fine over the weekend. The only thing we did was our weekly gas flow checks on Monday and I noticed the high output. I took out the collector to inspect the spring and the signal was still high without anything touching the spring. Does anyone know if there is anything else I should check or do I most likely need my electrometer replaced ?

Hello

What is the flow of each Gas?

Hydrogen: 40 ml/min
Air: 400 ml/min
Nitrogen: 25 ml/min
Helium: 1 ml/min

Even without the gases, the output is high

Hydrogen: 40 ml/min
Air: 400 ml/min
Nitrogen: 25 ml/min
Helium: 1 ml/min

Even without the gases, the output is high

Ok, the problem you may have is that the electrometer is touching something metal or is failing, if you want to send me an email to henry_lp04@hotmail.com and if you can disarm the detector I can tell you by whatsapp what tests you must do to discard that it is the circuit of the electrometer that is damaged.

Usually this is caused by damage to the spring, by removing / replacing the collector. Check to see if the spring is coiled nicely (tight), or if has been stretched like an old slinky.

Thank you everyone!

I'm having the same problem with a FID on a 7890. It all started by me trying to physically measure the flows through my detector (wouldn't light). I put my Agilent sampling gizmo into the chimney of the detector like I have a thousand times before to sample the gas flow through my electronic flow meter and the detector shorted out like this. I'm not what you'd call a rookie with this stuff. I rebooted the GC from scratch, didn't help. I took it apart and cleaned all of the parts (jet too). Put it back together and same result. I've taken it apart and assembled it 4 times in all. Same result.

The spring looks good. I can't see or feel where it's hitting anything. This instrument is only 4 years old. Any other ideas?

The spring looks good. I can't see or feel where it's hitting anything.

I used to use a jeweler's screwdriver or small pocketknife blade to make sure that the spring was positioned into the groove on the collector when I reinstalled those on 5830 and 5840 and 5890 and 6890 units. This was important.

That's what I do too. Once the collector is in place, it shouldn't be easily pulled out. That's how mine is behaving. It all goes back together smoothly. Still saturating the output.

Did you try pulling the column out of the FID and plugging that? I think we used a paperclip in a ferrule for that.

Do you get the crazy default number as the output ? I can't remember what that number is, but we got that a couple of times when someone assembled the collector wrong.