Fragmentation of Fluorescence Dye Labels Activated by Collisions or Photons

摘要

The isotopic labelling of Rhodamine B as well as high resolving mass spectrometry show beyond any doubt that the loss of a carbon dioxide is not a the reaction observed in xanthene dyes as was falsely published even recently. This extends even to other samples with the same structural motive. Even more this can be extended to aromatic acids in general. A quick survey of published mass spectra in several catalogues shows that the loss of CO from aromatic acids molecules, either protonated or as radical cations is indeed a2 very rarely observed reaction. The loss of carbon dioxide in these compounds is usually a high energy process that does not take place unless supported by rearrangement processes like the ortho-effect and other. The same is already explained by well-established text books on mass spectrometry. The airy use of fragmentation pathways based on a solely evaluation of the neutral structure can easily lead to a grossly false interpretation of mass spectra. The use of high mass resolving mass spectrometers is in such cases a fundamental prerequisite. Even there the deduction of structures should be done with extreme care. Authors and editors should be aware of this experimental necessity.