Chromatography Forum

Hello Everyone,

Recently, I found some ghost peaks with high intensity around several hundred kcount in my MS profile even though several runs without any injection were performed. The library search results indicate those peaks be cylco-solixanes.

The weird thing is that those ghost peaks disappeared after several isothermal runs at higher temperature than 200. Then they showed again when I run the blank started from low temperature like 50 to high temperature.

However, what I read about column bleed says that it mostly like a continuous baseline drift. Has anyone experienced this problem before? Is the problem I met here another kind of column degradation? What's your good suggestion get rid of the problem or do I have to purchase a new column?

Yes, column bleed is broad, and you seem to be describing distinct cyclosiloxane peaks. These usually come from your septum/inlet, which then travel through the column and deliver sharp peaks.

You're right. We also assumed that the peaks were caused by injection insert and septa. However, they still existed after we changed a new septum and washed the glass insert with solvent.

Also, the major ions shown in the mass spectra of ghost peaks are 282, 355,356, 430. Their retention times were quite reproducible during the temperatue programmed blank run from 50 to 260 degree while the instensity can drop down to certain level after several runs.

Any suggestion of this problem will be useful. Thanks.

Best wishes, Kai

Check that you really have flow out through the septum purge, and that there are no fragments of septa in the bottom of the inlet body below the glass liner.

Peter

Are you doing an injection for the blanks? One often overlooked souce of siloxonanes is from vial septa, and from rinse vials. The contamination from rinse vials can be very significant, especially if vials are topped off instead of being rinsed with solvent before refilling.

we have as well when injecting a blank recently, we ordered a detector and inlet cleaner, when i took the inlet apart i found a chunk of septa in the liner that has caused some similar problems in the past. i cleaned it and scored the guard where the septa was stuck and put it back together. we had some of the same issues, so i attributed it to the FID having some build-up on it.

wash glass insert with solvent, you will fix the problem. same we had once on schimadzu 5010