Chromatography Forum

Hi All,

I have been running a method for a while which has suddenly shown a large reduction in sensitivity. I am running at an EIEnergy of 69.9, Emission 34.6. I perfrom an autotune after each start up and have noticed a steady increase in EMV until today which is now at ~2900.

The increase in EMV coupled with the decrease in sensitivity suggests to me that the EM Horn/Filament requires changing.

Could someone confirm this for me or possibly suggest any other causes.

For information, the samples are very clean and the source appears in a satisfactory condition.

Thanks in advance.

the Agilent MSD system usually come with 2 filaments that can be switched in the software. see if you can switch to the second one. If the problem still persists, I would looking to pumping down and cleaning the source. If the EMV is still high, look into getting a new filament. I would not replace the horn unless needed because they usually run around $1200.

Thanks for the quick reply,


I have changed to filament 2 with the same result unfortunately. I will clean the source tomorrow and let you know the result.

Thanks for the info on the horn, if cleaning the source fails I will change the filament first!

Hi again,

I cleaned the MSD source with no inprovement seen. I have now replaced both filaments and when I run the autotune the EMV is still more than 2900. I have tried a few injections through the GC and the sensitivity is stiil poor (on scan mode I can barely see the solvent front, the GC does seem to be functioning properly and gas is coming through the column).

Any suggestions?

Thanks in advance.

EDIT:

It is now failing to complete the autotune with the error 'non-constant peak widths'

Hi there,

I had similar problems with the GC 6890 MSD 5973 I'm using following a power cut early this year.

I did the same things as you (source clean, swapping inlets, swapping filaments, half-turn of EM etc.) and nothing improved until I cut 5cm off the front of my column and removed the quickswap and transfer line and just plumbed the column straight through to the MS.
My EM runs quite high too (~2500) but its actually fine.
Just keep trying different things, something will work eventually.

Maybe if you list each thing you've tried and we can suggest some more ideas?

cheers
Liz

If your Electron multiplier horn have 2900....change it.
3000 is the maximum
That's your problem

Hey,

It could be a corrupt tune file. Our tune files looked terrible and we were having to abort the tunes as the EM volts were getting too high in the tune.

Try loading an old tune file.

Hope it works