I have a method that no matter what I do I seem to get persistent carryover that doesn't reduce after multiple diluent injections. Has anyone come across materials binding to the rheodyne and then being washed off at a later time? Any suggestions?
We are running on 1200 and 1260, quaternary pump, DAD detectors.
The compound of interest in this case is Trifluoperazine HCl, running phosphate buffer with triethyamine and ACN gradient.
The column is an Agilent Poroshell 120 EC-C18 2.7µm 50 x 4.6mm
The method has been validated for product license requirements.
The issue was seen during the development and validation process intermittently however we were never able to get to the bottom of the issue.
Sometimes we don’t see any ‘carryover’, sometimes we see a small amount, this time I have seen ~1%
I’m at a bit of a loss to explain it so welcome almost any suggestions.
Just this compound, though there are multiple compounds in the solutions.
And no, both diluent injections and blank gradient runs don’t show significant reduction of the peak in question.
If we very thoroughly clean the system, this seems to improve the amount of the peak present, but it does seem to increase again fairly rapidly. We can sometimes squeeze out a run before the peaks gets problematically big.
The development analyst tried multiple syringe washes including IPA to clean up between injections with no luck
Maybe bypass the autosampler, by connecting tubing from the pump directly to the column/column compartment. Perform blank/no injection runs (no samples since there is no flow through the autosampler) If this helps, then the problem is the autosampler. A worn rotor in the autosampler can contribute to carryover.