the library search score for a compound is different with different instrument

Question

.the library search score for a compound is different with different instruments

nowadays,in my work we have different types of gc-ms, we bought new gcms 7890B- 5977B HES , when comparing the result of the same sample (of course with different dilution ) between gcms 7890B- 5977B HES and the gcms 7890B- 5977B inert source we found different ion ratio and this leads to different lib search score. the gcms 7890B- 5977B HES gives lower score with the same setting for method of acquiring and processing .we still depend largely on the match score.

so i wounder if this is normal, and if not , how i overcome this issue

thanks alot

garyb007 · Answer

I would say this is normal, it would be impossible to exactly match spectra between 2 different instruments.

pwd · Answer

Hi,

as garyb007 said, with two different instruments (different hardware) it is impossible to get the exact match.

It is most likely related to the background created by using different hardware.

i.e. different columns or more or less used ion sources or multipliers create different height of background

smathers · Answer

As each system tunes slightly different, you will see varying scores. That being said, the larger difference you are observing most likely stems from the difference in tuning between an INERT source and the newer style HED source. If you compare the tune files between both sources, you will see how much they differ.

added to this, most library spectra was was not captured using the HED source, so your scores will definitley not line up as well, by default.

If this becomes an issue, you could create a custom library to be used for the HED source, which is a great alternative if you are not looking for unknowns.

the library search score for a compound is different with different instrument

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