Two-dimensional correlation spectroscopy techniques applied to ion trap tandem mass spectrometric analysis: nitroaromatics

The technique of two-dimensional (2D) correlation spectroscopy is combined with ion trap tandem mass spectrometric (MS/MS) analysis to provide insight into the energetics and behavior of gas-phase ions. The 2D correlation method is demonstrated by the analysis of the fragment ions produced by the fragmentation of molecular radical cations of nitrobenzene and m-nitrotoluene at a series of applied potentials that effect collision-induced dissociation (CID). The asynchronous correlation intensities show that competitive loss of NO to form [M-NO]+ proceeds at a lower CID energy than loss of NO2 to form [M-NO2]+. The formation of the ion corresponding to [M-NO-CO]+ is shown by the method to occur at a lower CID energy than the formation of [M-NO2]+, but at a higher CID energy than [M-NO]+ for both nitrobenzene and m-nitrotoluene.