Chromatography Forum

Hi all,

Recently we use ion exchange column to analyze anions such as NO2, NO3 and Chloride. But the food sample are, e.g. milk, cheese, pork and meat..... Hence we start to worry about the fat will "coat" on the active site for ion exchange.

Indeed the peaks RT start to move earlier and earlier (but still have a good peak shape). Does it mean the column start to turning bad?

And, would you please suggest some methods that we can clean those fat, protein stuff?

Thanks for all inputs!

SPE.

Anthony; the cleaning procedure with depend of what kind of Column you have; but at least I would add temperature besides the manufacturerr recomendation. High temperature expand the pores and help to realse everything.

What kind of Equipment are you using and how many dirty saple do you inject? there are several sample perp procedure taht could help you; Metrohm for example have Dialisys systems that could be easier than SPE. You need a precolumn; and sometime a quick extraccion with a solvent will help you to eliminate Fat; you dont need and extraccion funnel for this just a test tube (make it easier...)

There are two issues here: fixing the problem, and preventing it from happening again.

The fix depends on exactly what kind of column you have. If it is a bonded-phase column on a silica substrate, you may be able to reverse-flush the column with something that will solubilize your fatty materials. Isopropanol, or perhaps isopropanol with some methylene chloride. If you do this, be sure that you keep the flow rate low (IPA has a high viscosity), and make sure that when you switch solvents, everything is miscible (e.g., aqueous buffer - water - IPA - IPA+MeCl2 - IPA - water - buffer.). There is, of course, no guarantee that you will be able to get the junk off, and it may be cheaper to simply replace the column.

If the column is a resin-based material, then this sort of non-polar solvent rinse has a high risk of swelling the resin and killing the column. I would contact the column vendor for advice on regenerating that type of column.

Prevention has already be covered in the previous posts: a guard cartridge as a minimum (if all else fails, its a lot cheaper to trash a cartridge than an analytical column), SPE, liquid-liquid extraction, etc.