Radical ions and dehydro cations in detection of 2,3′-bisindolylmethanes using electrospray mass spectrometry

•[M]+ and [M−H]+ ions of 2,3′-bisindolylmethanes were detected using ESI-MS.•The processes forming [M]+ ions occurring in droplets were investigated.•The formation processes of [M]+ and [M−H]+ ions were independent.•The fragmentation differences between [M]+ and [M−H]+ ions were compared.

A series of 2,3′-bisindolylmethanes were analyzed using electrospray ionization quadrupole time-of-flight and radical ions ([M]+) and dehydro cations ([M−H]+) were detected in positive-ion mode. The formation pathways of [M]+ were proposed confirmed by D-labeling, free radical trapping and CID-MS/MS experiments. It was found that [M]+ ion was formed in droplets by the direct loss of an electron and the processes forming [M]+ and [M−H]+ ions were independent. The fragmentation pathways of the [M−H]+ and [M]+ ions were studied by CID-MS/MS. The dominant fragmentation pattern of [M]+ ions is the loss of benzyl radical comparing to that of [M−H]+ ions.

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