Mainz 2017 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 3: Resonance Ionization MS and others

MS 3.6: Vortrag

Dienstag, 7. März 2017, 12:45–13:00, RW 2

Distinction of structural isomers by means of chirped femtosecond laser ionization — •Viola Krein, Nicola Reusch, Nikolaus Wollscheid, and Karl-Michael Weitzel — Philipps-Universität Marburg

Structural isomers of disubstituted benzenes are difficult to distinguish with most mass spectrometric methods, in particular when both substituents are identical. In those cases, a distinction is possible by coupling mass spectrometry with a chromatographic method. An alternative approach is the combination of femtosecond laser ionization with time-of-flight mass spectrometry (fs-LIMS). Here, the variation of several laser pulse characteristics opens access to a multidimensional analytical technique. In the current work we present a systematic chirped fs-LIMS investigation of two different ortho-, meta- and para-disubstituted benzenes, i. e. difluorobenzene and benzenediamine. In both cases the mass spectra for the three structural isomers look similar for transform limited laser pulses. By systematic variation of linear and quadratic chirp we are able to enhance small differences between the ortho-, meta- and para-isomers for specific fragments. Ultimately, we demonstrate, that we are able to distinguish the three structural isomers. In this context we will address i) differences in intensity-driven vs. non-intensity-driven fragmentation channels; ii) the mechanism for the formation of specific fragments; and iii) the relevance of a ring opening as start of the fragmentation process, as it is known for difluorobenzene [1]. [1] A.-M. Boulangera, D. M. P. Holland, D. A. Shaw, P. M. Mayer, J. Am. Soc. Mass Spectrom., 20, 20-24, (2009)