A method for effectively causing charge-remote fragmentation (CRF) when the structural analysis of an nitrogen-containing organic compound is performed using a high-energy collisional-induced dissociation-mass/mass spectrum (CID-MS/MS spectrum), a reagent to be used in such a method, and a method for analyzing an organic compound by the induction of CRF are provided. The method for the induction of charge-remote fragmentation (CRF) using a high-energy collisional-induced dissociation-mass/mass spectrum (CID-MS/MS spectrum) has the step of: introducing a squaric acid residue into an end of a nitrogen-containing organic compound. The squaric acid residue is represented by a chemical formula (I): ##STR00001## The reagent is provided for introducing such a squaric acid residue. Furthermore, the method is provided for analyzing such an organic compound by the induction of CRF.