What is ECD? ECD is short for Electron Capture Dissociation, a powerful method that fragments peptides and proteins while leaving post-translational modifications such as phosphorylation intact. Some examples: CID vs ECD of a Doubly Charged Phosphotyrosine-containing peptide. Complete Top-Down sequencing of Ubiquitin on a Q-ToF. Golden Doublets from ECD and CID performed simultaneously.