Chromatography Forum

Hi all,

Figured I would try out my luck here. I have been having a recurring issue with my Agilent GC-MS (GC 7890A and MS 5975C) where my samples will look good for a while, and then randomly the baseline will start to have troughs and negative peaks. Myself and service engineers have gone back and forth ruling out several flow and electronics issues.

Anyone ever have something similar occur? Tunes are looking ok with no leaks, however the m/z 219 abundance is above the m/z 69 by around 10%. The steps we have take so far include:

-New column
-New fittings and consumables (unions, nuts, liner, septum, gold seal, etc)
-With a guard column and without
-Cleaned the source
-New EM power supply
-New HED

Any help or suggestions would be appreciated!

Hi all,

Figured I would try out my luck here. I have been having a recurring issue with my Agilent GC-MS (GC 7890A and MS 5975C) where my samples will look good for a while, and then randomly the baseline will start to have troughs and negative peaks. Myself and service engineers have gone back and forth ruling out several flow and electronics issues.

Anyone ever have something similar occur? Tunes are looking ok with no leaks, however the m/z 219 abundance is above the m/z 69 by around 10%. The steps we have take so far include:

-New column
-New fittings and consumables (unions, nuts, liner, septum, gold seal, etc)
-With a guard column and without
-Cleaned the source
-New EM power supply
-New HED

Any help or suggestions would be appreciated!

Have you checked the wire connecting on the outside of the analyzer that powers the HED? We had one once doing similar things and the pin in that wire was broken and stuck in the interface ( or the other way around). We replaced the wire and the pass through connector, which is really easy it just has an o-ring and screw on nut to seal the connector in the analyzer door. It it the large diameter white wire with red ends if I remember correctly.

Have you checked the wire connecting on the outside of the analyzer that powers the HED? We had one once doing similar things and the pin in that wire was broken and stuck in the interface ( or the other way around). We replaced the wire and the pass through connector, which is really easy it just has an o-ring and screw on nut to seal the connector in the analyzer door. It it the large diameter white wire with red ends if I remember correctly.

Hi James,

Thanks for the suggestion! I vented down this morning and checked all the electronic fittings and all seemed to be in good shape with no broken prongs. I did have a small piece of dust fly out when cleaning one fitting so maybe that was impeding a connection? We'll see. Crossing my fingers