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- Posts: 4
- Joined: Fri Mar 10, 2023 12:41 pm
- Location: Denmark
I have been running my mobile phase for months now on our ELSD system with zero issue, exceptionally stable baseline at 5 mV. All of a sudden, with 2 new batches of mobile phase prepared, it just gives a very noisy baseline at 25-30 mV that oscillates wildly. The system needs to be cleaned with water whenever i try to pump my mobile phase through, or else the noisy baseline stays. Water gives a stable baseline, even 50:50 ACN:water gives stable baseline. But when I run my mobile phase again (see below) it just goes back to this highly variable noise level. I have tried discarding and making new mobile phase twice. It makes me suspect some sort of salt precipitation issue? I dont understand why this happens now and not the countless times ive run it before. I vacuum filter the mobile phase every time using a .45 µm filter, never had issues with that before. The only thing we did was switch supplier of mobile phase solvents. However, seeing as both are reputable suppliers and its the same gradient grade solvent, I cant see how that would be the issue.. any help is greatly appreciated! I am at a loss.
System:
Sedere - Sedex 90 LT-ELSD
3.5 bar - nitrogen - 94 degrees
Mobile phase:
MeOH:ACN:Water (53:24:23) + 30 mM ammonium acetate.
0.7 mL/min
no coloumn attached.