Chromatography Forum

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.

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.

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?