The New Fluorescence Enhancement System Eu 3+ -ARADE-HMTM-Al 3+ and its Analytical Application

Abstract

A new bis-Schiff base ligand, N,N′-bis-(4-N-aminothiourea-2-amylidene)-4,4′-diaminodiphenyl ether (ARADE), was synthesized. Its complex with Eu3+ in DMF emits the intrinsic fluorescence of Eu3+. The fluorescence intensity of the Eu3+-ARADE system was enhanced about 60-fold by the addition of hexamethylene tetramine (HMTM) and potash alum. This is a new fluorescence enhancement phenomenon. The excitation and emission wavelengths are 375 nm and 615 nm, respectively. Under optimal conditions, the fluorescence intensities vary linearly with the concentration of Eu3+ in the range of 7.8×10−9–1.75×10−5 mol·L−1 with a detection limit of 5.2×10−9 mol·L−1, or with the concentration of Al3+ in the range of 3.1×10−7–9.7×10−5 mol·L−1 with a detection limit of 2.7×10−7 mol·L−1. The interferences of some rare earth metals and other inorganic ions were described. This method was applied to the determination of Eu3+ in high purity yttrium oxide and the analysis of Al3+ in alloy steel standard samples. The mechanism of fluorescence enhancement was also studied.