Chromatography Forum

I understand how pressure can drop (leak, air etc) but what actually causes the pressure to increase...I have been looking at our agilent, and its gone from a steady 215 bar, to 230 bar and now 243 bar..... All of these values are a LOT higher than i would like. Is it just due to the column being dirty or something?

What is your system pressure without the column?

If you've changed nothing in the analysis, and the pressure increase has been steady over a few days or so, check the PTFE frit in the purge valve - it might be clogged. You may also have a blocked guard column (if you're using one), or a fouled inlet frit on your analytical column (if not using a guard). I think those are the most likely culprits.

the best way is to look at a pressure chromatogram,
if the pressure increases steadily then it is most probably the mobile phase.
if it goes up in step, that will probably happen in the beginning of the run, and that is due to the samples which need better filtering most probably