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allowed and 'forbidden' GC solvents
Posted: Tue Mar 31, 2015 8:52 pm
by Cassandre-2015
Dear all,
I am using a gcmsms but it is more a gc question.
I would like to know which solvents are allowed to be used and which one should be avoided.
as far as I'm concerned, I know I can use hexane, dichlomethan, methanol,
I should avoid water (if I understood well, it is because of the expansion volume of it, it will too quickly overload the liner volume), acetonitrile,...
Is the polarity also an issue ?
many thanks
regards
Re: allowed and 'forbidden' GC solvents
Posted: Wed Apr 01, 2015 1:36 pm
by rb6banjo
I know that others have said water can be a problem but in my own experience, years ago, I had to determine 10's of ppm of methanol in some water and I didn't direct injections of water without a problem. Used a wax column as I recall. My biggest issue was not injecting too much so that it would blow out the flame. The project did not last long enough for me to evaluate how the water affected the life of the column.
I don't use acetonitrile as a solvent for direct injections so I can't comment on it. It doesn't seem to me that it would any more of a problem than methanol. This might be helpful to you:
http://blog.restek.com/?p=983
It's a good blog and it's free. Just give them your e-mail address and they'll let you know when something new is posted.
Re: allowed and 'forbidden' GC solvents
Posted: Wed Apr 01, 2015 2:18 pm
by Peter Apps
Water is better avoided if possible, but it is not forbidden.
As a general rule, you want a solvent that is chemically inert towards your samples, that elutes before your peaks of interest (there are exceptions), that is not so volatile that it evaporates quickly at room temperature but that is volatile enough to evaporate quickly in the inlet, and that is safe and not too unpleasant to work with - carbon disulfide is a brilliant solvent for FID because it is nearly invisible to the detector, but it is very volatile, terribly inflammable, it stinks and it is toxic. Ethers are good solvents but they are unstable when exposed to air and the stabilizers that are added can interfere with analysis.
Peter
Re: allowed and 'forbidden' GC solvents
Posted: Wed Apr 01, 2015 2:36 pm
by Steve Reimer
Peter has a good point, often it's the 'other stuff' in your solvent that is a problem. Watch out for preservatives and contaminants in your solvents.
Water not only has a large expansion volume but also can bring along salts. Chlorinated solvents typically have preservatives to scavenge the HCl by products. (What is that dichlorocyclohexane doing in my DCM?) Polar solvents can pick up variable amounts of water.
It's what works for your analysis.