A highly selective fluorescent sensor for Fe3+ based on covalently immobilized derivative of naphthalimide.

In this paper, the fabrication and analytical characteristics of fluorescence-based ferric ion-sensing glass slides were described. To fabricate the sensor, a naphthalimide derivative (compound 1) with a terminal double bond was synthesized and copolymerized with 2-hydroxyethyl methacrylate (HEMA) on the activated surface of glass slides by UV irradiation. Upon the addition of Fe(3+) in 0.05 mol/L Tris/HCl (pH 6.02) at 25 °C, the fluorescence intensity of the resulting optical sensor decrease, which has been utilized as the basis for the selective detection of Fe(3+). The sensor can be applied to the quantification of Fe(3+) with a linear range covering form 1.0×10(-5) to 1.0×10(-3) M and a detection limit of 4.5×10(-6) M. The experiment results show that the response behavior of the sensor to Fe(3+) is pH-independent in medium condition (pH 5.00-8.00) and exhibits high selectivity for Fe(3+) over a large number of cations such as alkali, alkaline earth and transitional metal ions. Moreover, satisfactory reproducibility, reversibility and a rapid response were realized. The sensing membrane was found to have a lifetime at least 2 months. The accuracy and the precision of the method were evaluated by the analysis of the standard reference material, iron in water (1.0 mol/L HNO3). The developed sensor is applied for the determination of iron in pharmaceutical preparation samples with satisfactory results.