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GCMS RT difference of analyte in different solvents
Posted: Tue Aug 02, 2011 1:02 pm
by Edde
I wonder if there is any difference in GC retention time if I analyze camphor in methanol or in BSTFA with TMS?
Camphor does not form TMS derivative, so I am measuring underivatized camphor in both solvents. The compound should elute just after the solvent front in my system.
Please comment. Thanks.
Re: GCMS RT difference of analyte in different solvents
Posted: Tue Aug 02, 2011 2:03 pm
by Peter Apps
In an ideal world each compound's retention time depends only on the column, the temperature and the carrier flow. In the real world solvent effects can shift peaks around - usually not by much - a few seconds would be typical. Sometimes this is enough to spoil an otherwise nice separation.
But as one of this forum's wise men once said; "Don't think, measure". Run in the different solvents and see whether the camphor peak shifts.
Peter
Re: GCMS RT difference of analyte in different solvents
Posted: Tue Aug 02, 2011 3:11 pm
by Edde
Thank you.
Actually, I find an RT difference when I measure a sample that is extracted by Toxi-A and reconstituted with BSTFA with TMS when compared with the RT registered with camphor in methanol some time ago. The difference is about 0.5 minute.
To ensure the shift isn't due to change in column condition, I shall run standard in different solvents as you suggested.