ECD offset held at -0.97mV

[azharrashid]

Dear All

I am having an issue with ECD. We have Perkin Elmer Clarus 500 GC with ECD and FID detectors. About three months ago I finished using ECD in very good shape. For three months I used FID with FFAP column for FAMEs and during this time ECD was fitted with Elite-5 colum. The other end of column was free. While using FID, ECD was remained off.

Now I wished to reuse ECD. But the signal on display is held on -0.97mV. i have tried to bake the column and have also changed the charcoal traps but there is no effect on the ECD offset. I shall be thankfull for suggestions and help.

Azhar

[Peter Apps]

Dear All

during this time ECD was fitted with Elite-5 colum. The other end of column was free. While using FID, ECD was remained off.

Azhar

So you had a column connected to the ECD, but the other end of the column was not connected to anything ? Was the free end of the column blocked off in any way ?. Did you have make-up gas running to the ECD while it was not working, was the ECD kept hot while it was not working ?

Peter

[azharrashid]

So you had a column connected to the ECD, but the other end of the column was not connected to anything ? Was the free end of the column blocked off in any way ?. Did you have make-up gas running to the ECD while it was not working, was the ECD kept hot while it was not working ?

Peter

Other of column was neither connected to anything nor that was blocked. Yes the make-up gas was running in ECD but the detector was not hot while I was working on FID.

Azhar

[Peter Apps]

Having the make-up gas running was good, but having the detector cold might have led to some condensation of crud on the inside.

Is the column that you are using the same one that you had in the oven and connected to the ECD while you were using the FID ? If it is you are probably getting lots of column bleed because the stationary phase was exposed to air at high temperature. The more you bake this column while it is connected to the ECD the worse the problem will get, because the degraded phases will bleed into the detector. You almost certainly need a new column.

What happens to the signal if you remove the column from the ECD and plug up the column connection with a nut and blank ferrule, and run it just with makeup gas ?

Peter

[azharrashid]

What happens to the signal if you remove the column from the ECD and plug up the column connection with a nut and blank ferrule, and run it just with makeup gas ?

I used different column while working on FID. I removed the column and pluged up the column connection with dead nut and the makeup gas was running normally. The signal sill remained on -0.97mV. I even did the baking at 400°C with column connection blocked and makup gas running. There was no change observed.

Azhar

[Peter Apps]

Having elimnated the obvious possible causes of the problem it is now time for some more sophisticated troubleshooting. I have never used the instrument that you have and so I cannot help you with that. Maybe it would be worth getting a service call.

Peter

[azharrashid]

Is it possible that ECD is too clean and the gas is also very much pure and we need to get it contaminated a bit like we do to remove active site on liners etc.???

[Peter Apps]

I do not think that this is likely. And if it was the case it would not be a problem. Have you autozeroed the ECD ?

Peter

[azharrashid]

Yes the ECD was autozeroed. I have baked the ECD again for abou 6 hours today at 450C with dead nut. But no change. For tomorrow I am thinking to inject some high chlorinated compound like lindane. Lets see if the ECD moves or not. Wish me good luck and thanks for your inputs Peter.

Azhar