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- Posts: 10
- Joined: Tue May 12, 2020 12:50 pm
I have a strange problem with the determination of two analytes.
I have a method on LC-MS/MS (MRM), 30 analytes - photoinitiators, which I transfer to QTOF.
All analytes, after small optimizations look excellent.
Scope of the method: 10 - 200 ng/mL
Mobile phase: pH=4 , ammonium formate / acetonitrile
I have a problem with two:
1-Hydroxycyclohexyl phenyl ketone CAS: 947-19-3
2-Hydroxy-2-methylpropiophenone CAS: 7473-98-5
These two analytes (unproblematically) are determinable by LC-MS/MS technique. I think I could even reduce the LOQ.
However, I do not see them using QTOF. What I would do, they only appear in the range of about 500 ng/mL - I don't understand why. Their monoisotopic mass is neither smaller nor larger than the others.
after creating a PCDL library, I search the analytes using the ALL IONS method (0,20,40 eV).
I have already tried with other eV, lower fragmentation energy, tried to create pseudo-MRM (Target MS/MS method).
I am out of ideas.