By Vicki on Tuesday, August 3, 1999 - 09:38 am:
After reading the LC Troubleshooting article in LC/GC April 1998 issue, I have been able to confirm that a ghost peak plaguing my chromatography is due to dissolved oxygen in my sample solvent. I've been able to remove it by degassing but it seems that oxygen is so readily re-dissolved, even from the headspace in the autosampler vial, that it returns within a matter of minutes. As the oxygen peak is co-eluting with a low level component of interest, I'd like to be able to remove it instead of re-developing and re-validating the method. Does anyone know of any additive, adsorbant or technique (short of working in an inert atmosphere) to remove oxygen and keep it out of sample solvent?
Relevant method parameters:
ODS column
Mobile phase: 20/80/0.05 v/v/v acetonitrile/water/TFA
Sample solvent: 50/50 acetonitrile/methanol (dictated by sample properties)
Detection: UV at 210nm.
By Tom Jupille on Tuesday, August 3, 1999 - 04:49 pm:
What about adding some ascorbic acid or sodium sulfite (or other antioxidant) to the sample to scavenge the oxygen? The catch would be to find one that doesn't create other interferences.
-- Tom Jupille / LC Resources
By J.K. on Friday, August 6, 1999 - 02:03 pm:
The method of degassing may change the
re-oxygenation rate. Generally the re-oxygenation
is, from fastest to slowest:
vacuum+ultrasound > vacuum > helium purging >
nitrogen purging > argon purging
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