Chromatography Forum

Recently I switched my mobile phase container from 4L to 18L one. The solvent levels are almost at the same height, however I observed higher background pressure and faster flow rate. The baseline curves a little bit after each injection. Is it normal to see such change? If the solvent almost used up, will the background pressure lower down and flow rate slower down? If in that case, probably I couldn't get consistent results. If I have to use the 18L solvent container, has it a way to solve it? Thank you very much!

Very strange. What flow rate and pressure are you observing? The inlet pressure is usually negligible compared to the pump pressure, and has no measurable effect on retention. Does the larger container have also a larger supply tube to the pump?

I use the same tubing. But the containor is sit on the bench, at the same height of the pump.

my flow rate is normal: 1 mL/min.

That is enough mobile phase for 12 days of nonstop running! Are you planning to go on vacation?

I was wondering if perhaps your supply line was restrictive and causing the pump to be inefficient with one reservoir. At 1.0 mL/min there should be no trouble at all.

Does a switch back to the original container also give the original pressure and retention?

Maybe someone thought it was an aquarium and put fishes in?
Seriously, what happens if you now place the liquid of the big container into the little one and running your stuff?

Mr. Mueller, I have ever shocked by a lab using huge plastic jug as their mobile phase (especially for buffer solution). I think its inner side will be difficult to be washed or cleaned. Especially if we put fishes in it.
That’s another problem in big container.