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: A: pH=4 , ammonium formate / B: 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.
LC-QQQ: Agilent 6460 (AJS ESI)
LC-QTOF: Agilent 6546 (Dual AJS ESI)*
Both methods have the same source settings.
Gas Temp: 350
Drying gas: 8 l/min
Nebulizer: 55 psi
Sheath Gas Temp: 400
Sheath Gas Flow: 12 l/min
VCap 4500 V
Nozzle Volatge 300 V
Fragmentor: 60 (also I tried higher)
* Oct1 RF Vpp 750