Cloud Point Extraction and Fluorometric Analysis of Eu(III) with Thenoyltrifluoroacetone and the Nonionic Surfactant Triton X-114

Abstract

The extraction of the Eu(III) thenoyltrifluoroacetone (TTA) chelate was investigated by using the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X-114, n = 8). A cloud point extraction (CPE) method is proposed for the preconcentration of Eu(III) and subsequent determination was carried out by a fluorometric method using a microwell plate reader. Optimal experimental conditions were examined for fluorescence of the TTA chelate in the surfactant phase. Fluorescence was measured at λ_em = 616 nm after excitation at λ_ex = 355 nm. The extracted species is estimated to be Eu(TTA)₃(Triton X-114)_1~2 and coordination is competitive between TTA and the oxygen atoms of Triton X-114 depending on each concentration. A content of Eu(III) was directly determined by a plate reader using 100 mm³ of surfactant phase without dilution. The fluorescence intensity, which was measured in a microwell, was a linear function of initial concentration from 1.0 × 10^-8 to 8.0 × 10^-6 mol dm^-3 of Eu(III). The use of microwell plate system is convenient for handling small-volume samples.