The fluorescent chitosan was prepared by the reaction of chito-san with fluorescein isothiocyanate (FITC), following the proceduredescribed by Qaqish and Amiji (Qaqish & Amiji, 1999). A 0.5 mg/mLsolution of fluorescein isothiocyanate (FITC, purchased from Sig-ma–Aldrich, purity 90% minimum) in methanol was slowly addedunder continuous stirring to a 1% w/v solution of the purified chito-san in 1% v/v aqueous CH3CO2H. The condensation between theisothiocyanate groups of FITC and the NH2groups of CH was al-lowed to proceed for 1 h, in the dark, at room temperature. Theensuing FITC–CH derivative was precipitated in a 10% NaOH aque-ous solution and washed with distilled water, until the total disap-pearance of FITC in the washing medium. In order to dispose of achitosan with a chromophore content which could be visualizedand quantified adequately by UV–Vis and luminescence spectros-copy, without altering the actual basic structure of the polysaccha-ride, only 2.3% of the amino groups of chitosan were modified inthis reaction, as determined by elemental analysis.