This axis concerns the development of analytical methods by tandem and multi-step mass spectrometry based on energy criteria during excitation and molecular fragmentation experiments by activation and collision. Building on the team's expertise in mass spectrometry and chemometrics, this approach is mainly used for the analysis of synthetic and biological polymers. The objective is to develop methods for the structural and quantitative analysis of isomeric compounds and isobaric contaminants for complex samples. This research area is also supported by DFT calculations which allow specification of the fragmentation mechanisms of the synthetic and biological polymers in the mass spectrometer.