Chromatography Forum

I'm an engineer working with Shimadzu instruments. One of our clients has one Shimadzu GCMS QP2010 plus and they are using GRACE column for MS.
The solvent that they use in their samples/standards is Methanol.

The problem we are facing is that we get to too many peaks that come from methanol and it is making very difficult the identification of the target peaks if they are close to peaks from ethanol.
We have tried many different grades of methanol and still too many peaks. When we use a different solvent ie acetone or acetonitrile the picture is much better with only a few peaks from the solvent.

Has anybody experienced the same problem? We suspect the problem comes from this type of column since we have tried new GRACE column and the same problem appears.

We have run the MS without any injections and we get no peaks at all. So GCMS is working normal.
We have tested the MS and it is working fine.

Can anybody explain why this is happening?

Thanks
Andros

There are a number of possible sources of these “peaks”. It could be contamination in the injection port of the column, contamination in the gas lines leading to the injection port or contamination on the head of the column.

I need a little more information. What do you mean by “GRACE column for MS”? Is GRACE the stationary phase, the manufacturer, what? If GRACE is the manufacturer, then what is the stationary phase, film thickness, and length of the column. When I did a Google search of “grace gc column” I was pointed to Alltech Assoc. who is a division of Grace, Davison, a business unit of W.R Grace.

Have you made an injection of the pure methanol? What type of results do you get? What is the temperature of the injector? What are the temperatures associated with the GC run? What is the size of the injection? Have you made an injection of air from the same syringe you use for the methanol? Is an auto sample involved?

My thought is that there is something in the injector that is very soluble in MeOH and is not that soluble in acetone or acetonitrile. What do the spectra of these GC peaks look like?

Also, are you injecting standard mixtures or are these sample extracts that are giving the problem chromatograms?