I am developing a headpsace residual solvent method and due to solubility limitations, I have to use DMSO as the sample solvent. When using water, most methods I have come across use an oven temperature of 80 C. When using DMSO, is it common to use a higher temperature since DMSO boils at approximately 189 C? I have tried to find a reference that lists the vapor pressures of common solvents at various temperatures so that I can compare with water but this has been unfruitful. Other than the risk of bursting the vial and sample degradation, is there any reason not to use DMSO at elevated temperatures (> 150)? I consulted Static Headspace Gas Chromatography by Bruno Kolb and DMSO as a solvent is not addressed. Also, any information regarding a supplier of high purity DMSO would be helpful. Volatile components present in the DMSO that I have used thus far are causing selectivity problems. Thanks in advance for your help.
By Ron on Friday, May 24, 2002 - 01:33 pm:
If I understand correctly, you are looking for other organic components dissolved in DMSO. I would try heating to 80 C to see if recovery is adequate. The vapor pressure of the analytes is the key factor, not that of the solvent. You should get reasonable recoveries using the same conditions used for aqueous samples.
DMSO purity is a real issue for this type of work. DMSO is very efficient at dissolving organics from the room air, so the solvent must be isolated from organic vapors during sample prep.
By Rod on Friday, May 24, 2002 - 02:51 pm:
DMSO is useful at 80°C in headspace work.
Be vigilant for DMS and DMDS peaks.
Recoveries are about 1/3 of those from water for many common organic solvents at 80-85°C.
NOTE: Heating DMSO at higher temperatures can drive unwanted reactions with the solvents of interest and the sample matrix, so be careful.
Unless you are looking for semivolatiles there is no reason to use higher temperatures.
Have you tried water/DMAc combinations for your dissolution solvent instead of DMSO, or perhaps methyl cellusolve?
Supelco Gas Separations Research
By Anonymous on Tuesday, May 28, 2002 - 06:23 am:
I had a coworker whose favorite DMSO replacement was N,N-dimethylformamide
By Anonymous on Wednesday, May 29, 2002 - 02:15 am:
Spectroscopic grade of DMSO by Merck is quite good.
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