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DMSO as Diluent
Posted: Wed Sep 07, 2005 9:59 pm
by jan
I know DMSO is not an ideal diluent for HPLC. It will distort the peak shape. Is there any theory or explaination about it? Thank you in advance.
Posted: Thu Sep 08, 2005 3:08 am
by james little
Don't know for sure, but probably just too strong a solvent and causes peak to move with DMSO before actually interacting with column/eluent.
We find DMF is a very good replacement for DMSO. Usually better to make up more concentrated solution and inject 5 ul than to prepare a diluter solution and inject 25 uls.
THF not a bad solvent, but not as good as DMF or DMSO for many of our compounds.
Also use TFA as a solvent. However, can't let compounds with alcohols sit for long time because converts some alcohols to TFA esters in about 1 hour. So prepare and inject fresh. Also, leave the tops off the bottles, because after one injection will dissolve silicones in top and give a lot of mass spec background ions.
Posted: Thu Sep 22, 2005 7:18 am
by syx
Are both safe enough for seal and PEEK?
Posted: Thu Sep 22, 2005 3:34 pm
by tom jupille
PEEK is incompatible with THF.
Posted: Thu Sep 22, 2005 7:14 pm
by unmgvar
Jan,
what type of peak distortion do you get?
Posted: Wed Sep 28, 2005 8:42 pm
by jan
Actually I never used more than 10% of DMSO in my sample so I did not have a peak shape issue. What I do is that I dissolve the sample with samll amount of DMSO then dilute it with my mobile phase. I just heard from other people that if you use only DMSO as a diluent and you will see bad peak shape. Anybody has real experience about that?
Posted: Thu Sep 29, 2005 2:44 am
by Bill Tindall
If the injection volume is small, 5 or 10 uL, DMSO is no problem. It is our preferred saponification solvent, so we have done bazillions of samples with DMSO.
It is a very "strong" solvent and viscous. I expect both these factors are a problem with large volume injections.