Reagent for fluorescent labelling of amines, amino acids and proteins. Synthesis: G. Weber, Biochem. J. 51, 155 (1952); A. Mendel, J. Chem. Eng. Data 15, 340 (1970). In amino acid analysis: J. Airhart et al., Anal. Biochem. 53, 132 (1973). In HPLC analysis of phenols: R. M. Cassidy, D. S. LeGay, J. Chromatogr. Sci. 12, 85 (1974). In protein microassays: T. Kinoshita et al., Anal. Biochem. 66, 104 (1975). In measurement of desquamation: R. Marks et al., Br. J. Dermatol. 111, 265 (1984).