Ghost peaks and sudden baseline shifts

5975C MSD and 7890 GC. I am fairly new to GC-MS and am having issues with my baseline. I have recently begun seeing ghost peaks and sudden baseline shifts after replacing a column. I did inlet maintenance and added an in-line gas purifier as well as conditioned the column to help resolve, but the bottom spectra which was run after this maintenance is actually showing the ghost peaks again as well as the sudden baseline shifts I saw before.

Could this be a detector issue? I have a CI detector but know nothing about how to clean or troubleshoot it.

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0 karrun over 3 years ago

Not really. I've listed the ghost peaks and the 18 and 40 abundance below. Please scroll over to the right to see all the numbers.

I did run an air/water check this morning and my N2 values are quite high. O2 and water seem okay. Not sure where high N2 would come from.

Forgive my ignorance, but what's the significance of m/z 40? I get that 18 is water.

Thanks for the help.

R.T. 18.440		R.T. 20.431		R.T. 23.574		R.T. 25.681		R.T. 33.717		R.T. 36.266
m/z	Abun	m/z	Abun	m/z	Abun	m/z	Abun	m/z	Abun	m/z	Abun
18.1	246272	18.1	3379	18.1	2132	18.1	2631	18.1	3719	18.1	4275
40	67416	40	93472	40	75032	40	76104	40	81128	40	84760

R.T. 38.685		R.T. 42.954		4R.T. 43.729
m/z	Abun	m/z	Abun	m/z	Abun
18.1	4546	18.1	5385	18.1	5602
40	86064	40	82256	40	80672

0 garyb007 over 3 years ago in reply to karrun

I am wondering if your gas is contaminated with Nitrogen (28) and argon (40). You have no 44 peak of CO2 which would indicate a leak. Is this an old column?
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0 garyb007 over 3 years ago in reply to karrun

I am wondering if your gas is contaminated with Nitrogen (28) and argon (40). You have no 44 peak of CO2 which would indicate a leak. Is this an old column?
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0 ravinduudugampola 13 days ago in reply to garyb007

How would I check the ratio of N2 to O2 to Argon? I think I have a similar issue and trying to determine the ratios to see if it is the gas tanks or contaminated cylinder.
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0 paulsalverda 9 days ago in reply to ravinduudugampola

In Manual Tune, PFTBA closed, set the scan range to 10-100, then click on the spectrum scan button. The spectrum will show repeatedly in the middle window to the left at the long red arrow..
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