Chromatography Forum

Thank you Mark for your reply.

I am using the system for more than two years in the same lab and location and it was working fine for that period of time. This is why I was eliminating any effect of airconditioning. I also do not use any online degassers for this system. I degass the mobile phase by sonication.

For these tests I replaced the column with a piece of tubing to get enogh pressure to operate the pump. However, the Noisy_baseline_4 was generated at really low pressure approaching the minimum limit.

At higher flow rates (0.5, 1.0 and 2 ml/min) I get a similar baseline to what it is shown in Noisy_baseline_3.

Hi mdyo,

This must be an air buble in the flow cell.
Flush with pure ethanol or methanol for 10 min - flow rate 5 mL/min.
Then try agin to run the last 2 chromatograms/conditions with water as a mobile fase. I'm quite sure you'll get a fine baseline.

Danko

It could well be that he is drawing air (gas) somewhere, continously. So if he gets it out of the cell he will have it right back in after "removal steps". Maybe he even has fleas as well as lice (dirt + air)? Anyway, I have seen only sawtooth repetition when air (gas) which was dissolved in mobile phase formed bubbles in the cell (bubble slowly increases, raising baseline, when big enough is flushed out with a sudden drop in baseline.....). If a resistor behind the detector (beware of cell pressure specs!) eliminates or diminishes this noise you will know....