What sources can cause column bleeding

[cay1000]

Hi everybody,

I am wondering what conditions cause column bleeding beside of low bleeding/ high bleed column.
Could you give me a piece of advice to avoid column bleed?

Thanks,

Kelly

[Don_Hilton]

Column bleed is the result of degredation of the polymer that forms the stationary phase in the column. To avoid bleed, you avoid things that will cause degredation of the column. Polymers can be damaged by heat, caustic chemicals, and oxygen -- particularly in combination. GC columns and LC columns have differing enviornments, so the advice for care is different.

I assume we are talking GC columns?

[cay1000]

Thanks!
Yes, I was wondering for GC column bleeding.

[Don_Hilton]

Check the manufacturers' web sites and they will have details on care of columns. Off the of my head:

keep oxygen out of the columns. Use high grade gas. Put a scrubber on it and keep the scrubber changed per schedule or use an indicating scrubber. Keep the septum changed on a regular basis and keep the ferrules snug - keep the instrument leak tight. And when the instrument is not in use, keep carrier flow through the column.

Do not apply excessive heat to the column. Use a GC ramp that gets the job done and clears high boiling residues from the column - and that's it.

Watch out what you put on the column. Dirty samples will have residues that will work their way onto the column. These residues may be reactive - particularly after being baked into the column and may accelerate polymer degradation. So no point in throwing junk onto the column just because you can.

Last point, remember that a GC column is a consumable. You will have to heat the column and unless you are running one of a very limited number of sample types, you will leave residues on the column. Keep in mind that an extra $5 per sample in cleanup will exceed the cost of a new column in just about 100 samples - which for some of us is less than a day's work. And if you can skip that $5 cleanup and the column gives good results for 200 injections and then dies, there are times when it is good to line the bottom of a trash can with a dead column.

Ultimately all columns will get old. They will bleed and they will die.