Matrix free laser desorption ionization coupled to trapped ion mobility mass spectrometry: an innovative approach for isomer differentiation and molecular network visualization

The chemical profiling of complex mixtures of natural products (NPs) is a major challenge in analytical chemistry and generally addressed by liquid chromatography coupled to mass spectrometry (LC-MS). In recent years also matrix free laser desorption ionization-mass spectrometry (LDI-MS) has become a versatile and time efficient complement to LC-MS. However, the absence of chromatographic separation in LDI-MS does not permit the differentiation of isomers. Providing a potential solution to this problem, the current work presents a combined LDI-Ion mobility spectrometry-tandem mass spectrometry (LDI-IMS-MS 2 ) approach, which facilitated the successful differentiation of four constitutional xanthone isomers namely butyraxanthone D, cratoxylone, garcinone D and parvixanthone G. In addition, the experimental collision cross section (CCS) distribution values of nine unreported xanthones are described. Based on these results, a proof of concept for the so far unexplored concept of a LDI-IMS-MS 2 based molecular network is being presented. • Differentiation of xanthone isomers by matrix free laser desorption ionization coupled to ion mobility spectroscopy and tandem mass spectrometry (LDI-IMS-MS2). • Experimental ion mobility data for nine xanthones. • Comparison of experimental and predicted CCS values. • Proof of concept for a molecular network (MN) based on LDI-IMS-MS .