Synthesis of novel fluorogenic Edman reagents, 7-N,N-dimethylaminosulphonyl- 4-(2,1,3-benzoxadiazolyl)isothiocyanate (DBD-NCS) and 7-aminosulphonyl-4-(2,1,3-benzoxadiazolyl)isothiocyanate (ABD-NCS).