I encountered some problems regarding the detection of (R)-(-)-N,N-Dimethyl-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine (CAS 55700-44-2) in mass spec. Its molecular weight is 441.33. I found during analysis two separated peaks: the first one has a molecular ion of 458.15, the other one is 397.
I found them both with acid mobile phase (A:water, B:acetonitrile, 0,1 % formic acid) and with basic mobile phase (A: ammonium bicarbonate 50 mM, B: acetonitrile). Even with direct injection in the mass I found the same species.
Has anyone experienced something similar with this molecule?
Could you please have some ideas of what was happened, or what are the possible jokes of this molecule?
Thanks
m/z 397 may be due to the loss of the N(CH3)2 group due to fragmentation
m/z 458 may be due to the formation of an OH or H2O adduct
Thank you both Daniel and Noel for the answers.
Noel W Davies Noel, You're right, I forgot to mention the ionization: I used ESI+. In the meanwhile I made some further analysis and in particular I infused the molecule directly in mass spec in 100% acetonitrile with and without formic acid (0,1%). The results was quite the same except that in this case, probably because I used another batch I saw the molecular ion at 441.4. I used a triple quad because at the moment I can not use the HRMS that could give me a more accurate mass, but the triple quad is quite calibrated. I don't know why I don't see the 442.13, but even in this case (https://webbook.nist.gov/cgi/cbook.cgi?ID=C102545&Mask=200#Mass-Spec) the main monoisotopic ion is 186.031 and the molecular ion seen in mass spec is 186, more similar to what I had seen. Probably I have a positive charge from the iron. I also saw a molecular ion at 221.4. Could it be the double charged derived from Fe2+? I don't have the chance now to look at the distance between the isotopes, but if they are at 0.5 it could be possible.
Why don't you favor the explanation of the loss of HN(CH3)2? for your information, the cluster of the isotopes related to 397 is similar to 441. 397 is also the more abundant ion in the spectrum.
Daniel Bernstein I thought about the formation of -OH as well, but I saw the 458 also in infusion with only acetonitrile. So, I'm wondering where it gets -OH...
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