Once again I am back to pick the brains of all LC'rs out there.
We currently use Waters C18 microbondapack 30cm columns for the separation of Irganox and Irgafos additives in Polyethylene, and over time the columns are suffering from bad peak tailing.
When a new column is installed we get an Asymmetry Ratio of ~1.1 but after a period of 7 months constant use, the Asymmetry ratio has risen to as much a ~4 for one of the components.
I have discovered an old historic method for regenerating the columns which is as follows:
"Flush Column with 50mls of each of the following:
2 Ethyl Acetate
5 Ethyl Acetate
9 Methanol/H2O Carrier"
This method was written in 1987 and I have never regenerated a column before, therefore I am looking for information on whether this is still a suitable method of regen, or whether there are more modern/easier techniques in use to regenerate C18 column used for this application?
Thank you all in advance for any replies!
By Real value on Wednesday, July 9, 2003 - 08:23 am:
What is cost of a "successful" regeneration in labor $$$ vs. purchase of a new column?
By Anonymous on Wednesday, July 9, 2003 - 09:59 am:
I agree with Real Value above. 7 months constant use seems very good value to me. Alternatively you could try using guard columns and replace those instead. Some people turn the column upside down and use it against the recommended flow direction. This can restore the performance but BE CAREFUL! Some manufacturers use a wider mesh at the top of the column than the bottom. Backflushing it could cause silica fines to enter your expensive detector. In any case, backflushing for a while before connecting to the detector would seem prudent.
Has anyone used this procedure out there?
By Real Value on Wednesday, July 9, 2003 - 12:01 pm:
We've had some real-life samples where small amounts of dissolved thickeners in the samples kicked out of solution in the mobile phase and eventually clogged up the column pores, causing high backpressures. These columns happened to be reversible so we did pump backward through them (not connected to detector) to wash out the clogs.
By Anonymous on Wednesday, July 9, 2003 - 08:22 pm:
Any general regeneration method is nothing but a wild guess on what the contaminants could be. If it works, be happy! If it does not work, you need to try to think for yourself, what could cause the contamination, and how it could be removed or prevented.
Otherwise, I agree with the other posters who think that you got good value out of your column.
By Tim on Thursday, July 10, 2003 - 03:46 am:
The cause of the tailing could be due to voids forming which revering can sometimes cure. However, it could be due to loss of the C18 groups from the surface of the silica, in which case any attempted regeneration is going to fail - the suggested method will only work if the column surface or frits are clogged up with other material from you sample matrix.
If you want to try regeneration using the polar->non-polar->polar column wash route, use an old gradient pump (quaternary) with the gradient programmed to progressively change the mobile phase. You will get best results if you monitor the progress on a detector, but need to ensure your wavelength will pick up anything being flushed off (or use RI).
All-in-all, I agree on the 7 months life from continuous use is good value, so just pressure the boss to let you have a new column!
By John on Friday, July 11, 2003 - 01:37 am:
There is quite a detailed article in this month's LC-GC on column 'restoration'.
By bookoon on Friday, September 26, 2003 - 04:44 am:
you may try the following link
By Anonymous on Friday, September 26, 2003 - 01:37 pm:
I agree with Real Value: 7 months is a wonderful column lifetime. How many injections did you perform? How many $$/injection did this column give you?
Let's say you did 5,000 injections on this $500 column. That $0.10 per injection. You want to now spend an afternoon trying to clean up this poor column. It served you well. Let it R.I.P.