Bioactive peptides are catching great interests for the last few decades. They find several applications such as preservatives in food chemistry and also as therapeutics. There are actually more than 60 bioactive peptides on the pharmaceutical market and this figure shows a yearly increase. Among these peptides approximately 2/3 are composed of macrocylic structures. This shape indeed usually improves the bioactivity of the peptides, their stability and their pharmacokinetic properties.[1] If some of those therapeutic peptides are cyclic analogues of linear compounds, some of them are natural cyclic peptides that can be found in various living organisms. In both cases, it is essential to develop robust, efficient and sensitive techniques to determine their structures and/or their quality after synthesis or purification as natural extracts. Depending on the origin of the compounds and, eventually on the synthetic procedure, peptides may have different forms that can lead to complications for the structural analysis. We have performed multistage mass spectrometric experiments on a quadrupole ion trap to evaluate the potential of CID MS/MS and Energy-Resolved Mass Spectrometry (ER-MS) for extensive structural information. Experiments were conducted on purely synthetic model peptides consisting in either simple macrocycles obtained by intramolecular end-to-end cyclization using click-chemistry [2] or with synthetic analogues of natural venom peptides from cone snails.[3] We have determined that an increase in the amount of structural information can be obtained: 1) by careful and appropriate tuning of the mass spectrometer CID conditions[4,5], and 2) by using specific methodologies such as the «Gas-Phase Collisional Purification»[6-8]. Here we show some preliminary results towards this direction. References 1. A. Zorzi, K. Deyle, C. Heinis; Curr. Op. Chem. Bio., 38, 24-29 (2017) 2. D. Jeanne Dit Fouque et al.; Anal. Bioanal. Chem., 410, 5765-5777 (2018) 3. J. Giribaldi et al.; Marine Drugs, 18, 150-163 (2020) 4. T.S. Neugebauer, A. Memboeuf; J. Am. Soc. Mass Spectrom., 32, 2685-2697 (2021) 5. A. Révész et al.; J. Proteome Res., 17, 5, 1898-1906 (2018) 6. D. Jeanne Dit Fouque, A. Maroto, A. Memboeuf; Anal. Chem., 88, 10821-10825 (2016) 7. A. Maroto, D. Jeanne Dit Fouque, A.Memboeuf; J. Mass Spectrom.; 1-11 (2020) 8. E. Logerot, G.Cazals, A. Memboeuf, C.Enjalbal; Anal. Biochem., 655, 114823 (2022)