A fluorescent chemical sensor for Fe3+ based on blocking of intramolecular proton transfer of a quinazolinone derivative.

In this paper, 2-(2'-hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), a typical compound that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesized and used as fluoroionophore for Fe(3+) sensitive optochemical sensor. The decrease of fluorescence intensity of HPQ membrane upon the addition of Fe(3+) was attributed to the blocking of ESIPT reactions of HPQ and quenching its fluorescence. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensor shows a linear response toward Fe(3+) in the concentration range of 7.1x10(-7)M to 1.4x10(-4)M with a limit of detection of 8.0x10(-8)M, and a working pH range from 2.5 to 4.5. It shows excellent selectivity for Fe(3+) over a large number of cations such as alkali, alkaline earth and transitional metal ions. The proposed sensor is applied to the determination of the content of iron ions in pharmaceutical preparations samples with satisfactory results.