Discussions about HPLC, CE, TLC, SFC, and other "liquid phase" separation techniques.

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dear all,
In one of our hplc methods, iam facing the problem of carryover from one injection to the other.If i give around some 6 blanks after each analyis i observed the decrese in the carryover area from one injection to another. i tried with the waters symmetry c8 and phenomenex c8 coloumns.
Mobile phases is 0.1%tfa and hfba and other is Acetonitile.
What do you use for your needle rinse?
The problem is more likely to be caused at the injection side than that it is a column/eluent problem.
I am curious to see if this carryover problem was ever resolved. I am currently running an HPLC method with 0.05% HFBA. The HFBA does show excellent separation for my parent compound and related substances as well as gives me adequate retention of an early eluter from the void volume. My problem is a carryover that I am seeing with the parent compound. I have isolated the carryover to the HPLC column. I have rinsed with 100% ACN (with 0.05% HFBA) and yet the carryover persists. I know it has to be the parent compound since when I change gradient, the carryover peak appears at the same retention time as the parent compound. If I switch over to TFA, then the problem goes away and I no longer have the carryover. However the TFA is not as good of a separator (2 carbon vs 4 carbon), the early eluter is much closer to the solvent front than I am comfortable with, and I see a much noisier baseline with the TFA. Any ideas of what might be happening or how to eliminate the carryover problem with the HFBA?
Here is a short article on the topic that I took from a class I teach. It may help you solve any carryover issues and is based on troubleshooting the fundamentals.

"Carry-Over (Carryover) Contamination in HPLC and LC-MS Systems"; ... on-in.html
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