Chromatography Forum

Dear Gentlemen/Ma'am,
I need an advice concerning 5-year old Agilent GC-MS 7890/5975C which m/z resolution performance has changed drastically just in one night. Day before chromatogram and spectra were quite normal (peak of trimethylsilyl ether of glycerol is shown) : Next mornig it changed to a helpless mess: Another example:
Autotune process aborted with the error: Last successful tune was performed June 17th
It could be noticed that the greater m/z, the poorer the resolution. Also, mass shift occurs and m/z assignment now incorrect.
The ion source and dynode cap were cleaned, but with no success. One thing - electron multiplier exit wire contact was poor, but after fixing gives no result as well.
What could happened to 5975C?
Thanks in advance!

It is either a very dirty quad from sample contamination or a fault in the mass filter electronics, which would be the side board on the analyzer.

You have massive abundance probably because of the very wide peak widths which is causing the distorted spectrum. Check to see if anything has gotten onto the wires inside that feed to the quads. If it started after having the analyzer open it could be the wires are now touching. I had a similar problem when I bumped the wires when closing up the instrument once and caused them to short. Moving them apart fixed it. You can also take the covers off the side board and examine it for any swelled resistors or capacitors which would indicate a failed board.

Thank you, James for your reply.
Agilent service engineer tried to resolve problem from the remote access to Chemstation by manual tuning and so on, but with no success. Now they suspect the same reason - the side board electronic circuit malfunction. I understand nothing in electronic circuits, so I'll wait for service does his work. I'll provide details here later.

Now they suspect the same reason - the side board electronic circuit malfunction.

The main reason of circuit malfunction can be dust. Try to blow out the side board and RF coils with compressed dry air.

sav, thank you for your reply. I'll try to do so.

Continuation of a story...
The cause of malfunction is finally found and it was a side plate G3170-60021. (The plate has no visible injuries). Replacement with a new one will costs to us approximately US $10,000. (From Agilent certified dealer). It seems, it is highly (at least 3 times) overpriced (ca. 10 per cent of a new 7980/5975c original cost). Maybe, anybody knows where it can be repaired or buy used in Europe? Any information is greatly appreciated.

Continuation of a story...
The cause of malfunction is finally found and it was a side plate G3170-60021. (The plate has no visible injuries). Replacement with a new one will costs to us approximately US $10,000. (From Agilent certified dealer). It seems, it is highly (at least 3 times) overpriced (ca. 10 per cent of a new 7980/5975c original cost). Maybe, anybody knows where it can be repaired or buy used in Europe? Any information is greatly appreciated.

http://www.agilent.com/store/en_US/Prod ... 3170-60021

Not sure where the markup comes from but here in the US the price is 1/4 of that purchased directly from Agilent's website. Shows price of $2281.45 when I search it here in the US. $10k sounds more like the price of the whole analyzer assembly(side plate, quads, source and side board).