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- Posts: 64
- Joined: Mon Dec 05, 2011 11:41 pm
Hello,
I am developing a method to run some perfluorocarboxylates on LC/MS/MS. System is an Agilent 6410. I am going direct into the MS with a syringe pump. Negative mode, parameters for capillary, gas, etc are "normal" (based on those seen in literature, see Benskin 2012 [http://www.ncbi.nlm.nih.gov/pubmed/22695697]).
I tune/optimize manually for new compounds. When I set a normal fragmentor voltage, say 20V, I see what I would expect - lots of molecular ion, a little bit of smaller fragments. I lock quad 1 onto that molecular ion in SIM mode so it's only looking at that ion. I then scan quad 2 while leaving the collision energy in the collision cell at 0. I see the majority (~65%) of the molecular ion breaks down into the expected product ion. But without any collision energy! When I ramp the collision energy, the optimal energy is from 0 to 2.
I understand that the perfluoro anion will be stable with or without the carboxylate - with all that fluorine there is a strong inductive effect. But I don't know why it happens so easily though. Perhaps the energy provided by the hot nitrogen is enough?
Is it legitimate to make an MRM method that uses 0eV collision energy?
Also, can you compare collision energies between manufacturers? You can see that Benskin had collision energies of 15-25 kV using an AB/Sciex API5000Q. kV isn't even the same unit that the Agilent 6410 uses.
I am developing a method to run some perfluorocarboxylates on LC/MS/MS. System is an Agilent 6410. I am going direct into the MS with a syringe pump. Negative mode, parameters for capillary, gas, etc are "normal" (based on those seen in literature, see Benskin 2012 [http://www.ncbi.nlm.nih.gov/pubmed/22695697]).
I tune/optimize manually for new compounds. When I set a normal fragmentor voltage, say 20V, I see what I would expect - lots of molecular ion, a little bit of smaller fragments. I lock quad 1 onto that molecular ion in SIM mode so it's only looking at that ion. I then scan quad 2 while leaving the collision energy in the collision cell at 0. I see the majority (~65%) of the molecular ion breaks down into the expected product ion. But without any collision energy! When I ramp the collision energy, the optimal energy is from 0 to 2.
I understand that the perfluoro anion will be stable with or without the carboxylate - with all that fluorine there is a strong inductive effect. But I don't know why it happens so easily though. Perhaps the energy provided by the hot nitrogen is enough?
Is it legitimate to make an MRM method that uses 0eV collision energy?
Also, can you compare collision energies between manufacturers? You can see that Benskin had collision energies of 15-25 kV using an AB/Sciex API5000Q. kV isn't even the same unit that the Agilent 6410 uses.
