Chromatography Forum

We evaluate a DFTTP tune on a GC/MS prior to analysis of samples under the 8270/625 method.

I run an MSD 5973.

Lately my PCP randomly dissappears from the tune chromatogram. I have done all sorts of maintenance including cleaning the source, installing new columns, new liners, new gold seals e.t.c.. The samples I have been running so far do not have any acid in them. I even ran the tune under the 8270 method instead of the usual DFTPP method and the PCP peak showed up for a 2 days and has now dissappeared again.

Any ideas as to what more I should do?

Thanks!

Hey,
If you're still experiencing problems....
What kind of column are you using? What levels is your instrument calibrated for and how do your acids look in the calibration (any acids missing for the lower levels?) Are you cleaning the injection port with MeCl2 as well as changing liners and seals? Using 50ng of PCP for tune?

Thanks for your reply Darb,

We found the problem to the our glass wool (fused silica wool), because whenever we took out the wool the peak would show up. However, even with new glass wool I still have the same problem (lost the PCP peak) when I never did in the months before that I used glass wool in my liners. This dirties my source pretty quick so I am still trying to get to the "source" of the problem.

Any ideas?

Are you being careful when put the glass wool in the liner or is it getting smashed? If your PCP peak is re-appearing after you take the glass wool out, it sounds like you're creating active sites when you put it in.

Darb that may be, because I noticed the problem after my glass wool puller/inserter broke and I had to use my fingers to stuff the wool into the liner.

Yea. Definitely get yourself another wool inserter. That wool has to be a little loose and in good condition or it'll create those active sites. Good Luck.

I would suggest only using a wisp of wool. The good news is that it does not break down PCP as badly and it helps the flash, the bad news is that it does nothing to protect your column. One of the labs I work with does not use any wool at all on their SVOA instrument.

Best regards.

I use a single taper direct connect liner with great results. I do 525 ( drinking water) and extract the samples via SPE cartridges.