Chromatography Forum

Happy New Year's all...

Question regarding ECD signal. I installed a refoiled ECD into my 5890 Series II and I get a signal reading of 14574 on the display. It fluctuates but goes back to 14574 if you touch the wire that connects it with the detector board insert. While trying to make sure the detector was seated, a little pressure on the top part of it (that little arm) made the signal go down to <50 (and then taking the pressure off, the signal went back to 14574).

What gives? Do I have a bad ECD? Bad connection?

I found this on another forum:
http://www.labwrench.com/?Home.readPost ... ackground/

The connectors on the 5890 ECDs are very touchy - you may have a loose or bad connection. If you wiggle it you should see a change in the signal level (actually, just touching it will change it). If you see no change then you probably have a defective electrometer - it is very easy to fry them inadvertently.

What do you guys think?

John

My money is on a bad connection - as an additional check that the electrometer is not picking up stray signal from your fingers prod the connecter with an insulator - something like a plastic ruler.

Peter

Peter-

as an additional check that the electrometer is not picking up stray signal from your fingers prod the connecter with an insulator - something like a plastic ruler.
Peter

A plastic ruler did not change the signal...

My money is on a bad connection -

Where do you think I should check?

Thanks!
John

Hi John

If poking the connection with an insulator does not change the signal then you do not have a loose connection. What seems to be happening is that the electrometer is picking up the electric field from your fingers. What happens if you hold your hand close to the suspect area but not actually touching it ? This points to a problem with the shielding, I am not familiar enough with the hardware that you have to suggest where the problem might be exactly.

Peter

Hi John

If poking the connection with an insulator does not change the signal then you do not have a loose connection. What seems to be happening is that the electrometer is picking up the electric field from your fingers. What happens if you hold your hand close to the suspect area but not actually touching it ? This points to a problem with the shielding, I am not familiar enough with the hardware that you have to suggest where the problem might be exactly.

Peter

Peter-

Placing my hand close to the top of the detector has no effect on the signal...

I've actually installed 2 different ECDs and had this same result both times. As far as the shielding, I've completely installed both detectors (with the metal cover around the bottom base and the metal cover on the top) and turned on the instrument to operating temperature, with no change in signal.

What do you think?

Thanks for replying!
John

Chemwipe,

Sounds like your ECD is grounding somewhere. The signal bar or the signal lead off the detector is touching something on the chassis. Try removing all of the covers and see what your signal does. Are you using capillary or metal columns?

Best regards,

AICMM

Chemwipe,

Sounds like your ECD is grounding somewhere. The signal bar or the signal lead off the detector is touching something on the chassis. Try removing all of the covers and see what your signal does. Are you using capillary or metal columns?

Best regards,

AICMM

AICMM-

With all of the covers off, the signal is still high. I took the ECD out of the (it was still connected with the lead) and held it above instrument, and the signal was still high.

Did you mean the chassis of the detector? The heavy block that holds it? Should I unscrew that?

Thanks,
John

Chemwipe,

If your detector is installed and the signal lead is not touching anything else but the signal bar, the other possibilities for high zero are a leak and the wrong make-up gas. You need to be feeding the ECD nitrogen or P5/P10 to get it to work properly. I would next re-install ECD and re-install the make-up adapter and then leak check the system. I would also confirm that you are feeding it nitrogen.

Best regards,

AICMM

Chemwipe,

If your detector is installed and the signal lead is not touching anything else but the signal bar, the other possibilities for high zero are a leak and the wrong make-up gas. You need to be feeding the ECD nitrogen or P5/P10 to get it to work properly. I would next re-install ECD and re-install the make-up adapter and then leak check the system. I would also confirm that you are feeding it nitrogen.

AICMM-

Do most people's GCs look like this?


Maybe it's just me, but this looks like a mess. Does the make up gas (N2) go into the top (where it says ECD A) and carrier gas (N2 also, right?) into the bottom valve?

The diagrams and black and white pictures in the operator's manual don't look anything like this.

John

Chemwipe,

You plumbing is not all that unusual for a 5890. It is really important, though, to have a good leak check around all those fittings and nitrogen is not the best gas to do that with. Better to switch everything to helium for a bit and leak check all the fittings with a good leak detective.

So what comes into the carrier A pressure controller and why does it go to the B detector flow controller?
Then, where does the ECD B out tube from the pressure controller go, to one of the filters or what?

Best regards,

AICMM

AICMM-

So what comes into the carrier A pressure controller and why does it go to the B detector flow controller?

It was air (labeled as such) going into the A pressure controller. Why was it going into the B flow controller? I don't know, this is an instrument I got used from another company. Maybe it was running a dual detector method prior?

OK - the way it was hooked up was air as the make up gas and nitrogen as the carrier - but the labeled air line was actually helium! So that explained the high signal on the ECD. I switched the lines and the signal came down from 14780 to 130.

As soon as the signal came back yesterday, I was back to getting a lumpogram (as seen in one of my previous posts)...

then this morning...get this...I start getting a "Tray malfunction" error before each injection now.

It's always something.

John

I'm not sure from this whether or not you have putting air into the column, if you have it is ruined.

Peter

I'm not sure from this whether or not you have putting air into the column, if you have it is ruined.

Peter

Peter-

It was actually helium (the helium line was labeled as "Air") that was going through the column.

John

Chemwipe,

Did you get the e-mail I sent with the name of the autosampler repair fellow?

Best regards,

AICMM

Yes sir, I did.

Thanks!

John