GC-TOF-MS solvent contaminations

[badrul]

Hi all.

I'm using GC-TOF-MS (LECO) and recently I've encountered contamination problem regarding the solvent I used (ethyl acetate, acetonitrile, and acetone). Whenever I inject acetone, there's always a sharp and intense peak of benzophenone coming out in the chromatogram. Is this normal? Furthermore, when acetonitrile or ethyl acetate were injected, intense peak of (Z)-9-octadecenamide was observed. Again is this normal? Is it because of the column bleed or leakage in the system? Hope you guys can enlighten me on this matter. Really appreciate all your help.

Thanks.

[Don_Hilton]

What do you see if you make a run without actually injecting anything? And again when injecting the end of the syinge without pushing the plunger? My guess is that you will not see much of anything - unless you have a dirty inlet, but that is easy to fix.

You will see contamination in solvents. If you have used a plastic pipette in any of the solvents, expect to see a lot of stuff in the background, because they have plasticizers in them and there are compunds added to some plastics to adjust surface properites and other characterisitcs that make the plastic items do their jobs well.

Other compunds are found in the solvetns because they were poured into a container that had been touched with a finger - perhaps in taking the clean glass from the dish washing area to put it away. And fingers have natural oils and may have hand lotion on them (to say nothing of a snack, just eaten at a desk).

Be sure that you are the one who has opened the bottles. Be sure that all glassware is clean and has no residues from fingers or dishwashing soap. And, yest you will see some contamination in some solvents. Check the grade of solvent you are using and look at the specificaitons. That solvent you are using that is 99% pure -- the other 1% is something.

[Peter Apps]

If memory serves that amide is a UV stabilizer (?) in plastics.

Peter

[badrul]

Dear Don,

Yup, you're absolutely right. There was nothing in the chromatogram if I run the injection without actually inject anything (manual injection). I guess the contamination really comes from the solvent itself, not the system or the columns.

Thanks guys for your input.