Re: Overloaded Column?
Posted: Wed Jan 18, 2012 1:20 am
How do you know your contaminant is not soluble in DCM?Today I ran a blank on the contaminated column when I arrived at school. I have a gradient that goes from 50:50 DCM:THF to 100% hexanes in 35 minutes. Nothing eluted from the column until 30 minutes when the hexanes are at about 90% (10% THF) and at that time a small amount of my contaminant molecules (30+ carbon fatty acids) eluted.
Following this I ran hexanes through the column for three hours (10 column volumes as you suggested Tom), I did not use DCM because my contaminant molecules are not soluble in 100% DCM. They are barely soluble in 50:50 DCM:THF.
Luke
Are you sure you're not dealing with a functionalized lipid (phospholipid, glycolipid) that is hopelessly bound to the column, perhaps undergoing slow hydrolysis or transesterification over time, liberating a C30 fatty acid?
As mentioned, I would be inclined to replace the column. A co-worker of mine once introduced some PTC as ion pairing agent (hexadecyltributylphosphonium bromide, I think) onto a polymeric RP column. Needless to say, it ruined it.