is sodium lauryl sulfate the culprit?

[sfe-co2]

mohan_2008, since your sample is made up with the mobile phase, I don't see that as a potential problem.

Try reducing your injection volume. Also, when you inject your blank solution (towards the end of your analysis), did the pressure return to 150 bar? Have a careful look at your prepared samples: did your analyte fully dissolve? Danko does have a valid point here....if the Vehicle SDS is not fully dissolved (or that the SDS is not fully ionized), that might well explain your pressure problem.

Good luck.

[mohan_2008]

Yes, Mr. Mueller,

After a thorough rinse with 90%ACN:10%Water:0.1% Phosphoric, the pressure goes down to 150 bar.

As soon as you inject the sample the pressure ramps up to 210 bar and stays there. It stays there till a rinse is performed to get it down to 150 bar.

Yes, it gets repeated. And, as a matter of fact - two columns were sacrificed since they could not be used for anything else.

Yes, sfe,

This method is not a great one. Infact, a problematic one. However, as it is fully validated (surprise, we did not see these problems earlier) -

1. we cannot modify the method while running sponsor samples. i.e., no change in injection volume etc.

The analyte is well soluble at our working range.

[HW Mueller]

It stays at 210 bar continuoously even if you don´t inject anything for a consoderable time or even if you inject only mobile phase, lets say 10 times in series? What happens if you stop flow over night, the next day it´s still 210?
The junked columns still worked for this system?