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- Posts: 3
- Joined: Wed Sep 22, 2021 4:28 pm
I use ammonium formate 25mM in water as mobile Phase A and acetonitrile with 0.05% acetic acid as mobile phase B; the elution is in gradient mode.
When i run analtsis with fresh mobile phase, on the first day for example, i have a response factor about 1 x 10e-5 for the standard and areas of around 70000 for the imputities. On the second day, i obtain a RF of about 0,7 x 10e-5 for the standard and areas of around 90000 for the impurities. On the third day i obtain a RF of about 0.5 x 10e-5 and areas of around 100000 for the impurities. And so on. When i renew the mobile phase, RF and areas return at 1 x 10-5 and 70000. The RF stabilizes at about 0,35 x 10-5 until the mobile phase finishes. I exclude the standard degradation because i prepare new standard solution everyday, in triplicate, and i always observe the phenomenon. Even the carryover is excluded by several tests.
What’s going on according to you?
Sorry for my poor english, i hope you can help me