CI Autotune/Sensitivity - Issue 5975 XL


our 5975XL is not performing according to the specifications when using Chemical Ionization. Our tune files look like the ones described in the following question: Sadly no resolution was found there.



We tried the following:

1. Swaping the gasline from A to B

2. Changing the gas supplier from Air Liquide to Linde (both methane 5.5)

3. Cleaning of the source

4. Using another source body from an older CI-Source

5. Baking out of source an quadrupole

6. Checking for leaks in EI mode. Nitrogen is about 4 %. Evaluation tune ist successful. EI ist working fine.

7. Changed the CI gasfilter.

An Agilent representative suggested filling up PFDTD. But if PFDTD might be emtpy we would not see any signal at all? For NCI sensitivity ist bad. That is especially the case for m/z above 500 (PBDE und PBB Analysis). PCI checkout as well as NCI checkout do not result in the right S/N. Both are way to low; at least 3 - 5 lower than what we should expect. Unfortunately last year our GC was upgraded with a new sampler an inlet (PTV), so we suspected that some problems may arise from this but all our measurements in EI-mode perform perfectly.

We hope that somebody has an idea on how to resolve this issue, because we need the MSD for brominated an fluorinated substances.

Thanks for any input concering this issue.

  • We found this same issue with our 5973N CI instrument - after taking it offline to clean the source the relative abundances of 267 and 599 in PCI fell from 76 and 55% to about 33 and 13%, respectively.

    We also noticed the entrance lens being "optimized" to a voltage of zero, inconsistent with the last acceptable tune. In manual tune (and eventually autotune) great peak shape and resolution could be achieved, but the previous relative abundances were not  achievable. One interesting initial error was "mass gain too high at this mass range" which was a new one for us, but this was remedied through manual tuning prior to the autotune.

    No leaks were found, and we tried similar troubleshooting as described including changing the filament and replacing the tune file a clean, default tune file from a fresh instrument configuration. We checked electronic connections including the source itself and the pass-through leads with no issues found. We also examined all of the wires and connections associated with the quadrupole and found no visible issues. The EM was early to mid-life with a tune value of ~1400 V.

    The only thing that returned the relative abundances of 267 and 599 was the replacement of the entire side panel (all electronics + quadrupole) from an alternate 5973 that was available to us. This is obviously not an ideal solution, but hopefully this helps others with this issue.

    As we could confirm that at least the source and source connections were ostensibly fine, I would tentatively suggest this could be related to the quadrupole and associated electronics, but obviously we are just users and can't really say anything more definitive than replacing the sideboard (and retaining the original source / tip seal) resolved the issue for now.

  • Thank you for your answer. After the installation of our new GC-MS/MS we have a spare 5975. So we could try to change the side panel in the future.

    While installing our new GC-MS/MS we asked the Agilent technicians to have a quick look at the defective CI system. All of them said that they have no experience in CI. They even had problems validating the CI capabilities of the new system. One of them ruled out the possibility that a too high gas flow might have damaged the gas controller. So maybe your hint concerning the side board ist correct. 

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