Hi, anyone have a suggestion on how to clean PS-DVB columns? We have a high temperature GPC system running polyethylene samples at 160 degrees celsius using TCB as solvent. After some months, the packing material turns black, i.e black in the inlet at the first column and slightly brown at the outlet of the last column. Something is probably adsorbed on the columns and maybe thermally degraded after a while. We don't think it will disappear if we just reverse the flow, any suggestions?

How do you know it is not the packing that turned black?

Well, I'm not sure, but then the packing should have becomed equally colored in both ends, and not black at the inlet and brown/yellow at the outlet. It seems that there must be something from the samples. It might of course be residues of catalyst which may cause some reactions on the PS-DVB particles (which probably also contains some unreacted vinyl group left from the polymerization process). If that is the case, then it should not be possible to clean them.