By Nick Penner on Wednesday, July 23, 2003 - 03:08 pm:
Hello,
I am having a problem with large peak humps to the right side of my HPLC peaks. The solution I am injecting consists of a thioester with a trifluoromethylphenoxy group and the thioester alkene after the trifluoromethylphenoxy group and a hydrogen have been eliminated with sodium hydroxide (which was subsequently quenched with acetic acid). The solution also contains sodium perchlorate and the solvent is a 5:1 ethanol/water mixture. I have tried injecting both the thioester and the thioester alkene in this solvent individually (without sodium perchlorate) and the peak shapes have appeared fine. I appreciate any insight. Thank you.
Nick
By Nick Penner on Wednesday, July 23, 2003 - 03:32 pm:
Also, the column is a hypersil ODS HPLC column with 100mm length, 2.1mm diameter, 5um particle size and 1ul injection volume.
Thanks again.
Nick
By Anonymous on Wednesday, July 23, 2003 - 06:00 pm:
What is your mobile phase?
By Nick Penner on Thursday, July 24, 2003 - 07:30 am:
My mobile phase is 70:30 methanol:water.
By Anonymous on Thursday, July 24, 2003 - 03:13 pm:
Try to dilute your sample 1:1 or even 1:2 with water and inject again! See if this makes it go away!
By Nick Penner on Friday, July 25, 2003 - 07:48 am:
I still get the same problem. I don't see how it could be a problem with the column since it is only a couple of months old. Any other suggestions?
Nick
By Anonymous on Sunday, July 27, 2003 - 02:29 pm:
If it is a column problem, the humps on all peaks should look similar. Also, if you inject a standard (like the sample with which the manufacturer tests the column) and get the same humps, the column is dead. This can happen from junk in the sample, the mobile phase, pump seals etc.
By tom jupile on Sunday, July 27, 2003 - 03:40 pm:
Nick, if I read your original post correctly, the problem does *not* occur when you inject the analytes individually without added perchlorate. That would seem to eliminate "physical" problems with the column (as suggested by the most recent anonymous post) and implies some sort of chemical problem.
If this were my problem, I'd try to answer the following questions:
1. Is this a "new" problem (i.e., has this method worked for you before, and now you are seeing the problem on one column)?. If so, the most cost-effective solution may be to simply replace the column rather than wasting any more time and energy.
If you are developing the method and the problem has been there all along, then:
2. Does the peak shape problem appear when you inject a mixture of your analytes without any perchlorate? If so, then the problem is related to some chemical interaction between the analytes (you have already established that they are OK individually). At that point, you have a real "detective mystery" on your hands.
If peak shape is OK when you inject the mixed analytes, then it's related to the perchlorate, so:
3. How much perchlorate has to be in there before the problem appears? and how much do you need for other purposes?
Hope this helps!
By Travis Ruthenburg on Sunday, June 6, 2004 - 07:46 pm:
I don't know, if I have read the Mudd bathroom literature correctly, it seems that you probably have dissolved the column.
You have dissolved the column, Nick. Deal with it.