Sorption-luminescence method for determination of ytterbium

Abstract

Yb(III) ions, complexed with some organic ligands, exhibit intense luminescence. The light energy is absorbed by the organic part of the molecule of the complex, then there is an intramolecular energy transfer from the organic ligand to the Yb(III) ion. During the sorption of Yb(III) on the solid matrix, the intermolecular energy transfer is suppressed, which provides the increase of the luminescence intensity, and the effect of selective preconcentration is achieved. Promising materials for solid-phase spectrofluorimetry are natural zeolites. Sorbed Yb(III) on these natural nanomaterials retains the ability to interact with organic ligands. In order to develop a sorption-luminescent method for the determination of Yb, the ability to luminescence of Yb(III) ions sorbed on natural Transcarpathian clinoptilolite in combination with 1-(2-pyridylazo)-2-naphthol (PAN) was studied. Luminescence composition «clinoptilolite-Yb(III)-PAN» is observed in the IR region of the spectrum with a maximum λ=978 nm. Luminophore samples were excited by a laser with λ=532 nm. The optimal conditions for obtaining this luminophor have been found. To prepare an effective luminophor «clinoptilolite-Yb(III)-PAN» it is necessary to use precalcined at 300 о C samples of clinoplololite, heated at 50 о C samples «clinoptilolite-Yb(III)», and the final luminophor heated at 50 о C. Sorption of Yb(III) on clinoptilolite is carried out from weakly alkaline solutions at pH 9.0. The developed sorption-luminescent method allows to determine Yb in the presence of 10-fold excess of La(III) and Eu(III), as well as 5-fold excess of Lu(III), Tm(III), Gd(III), Pr(III), Tb(III) with a detection limit of 5.0 ng·mL -1 . The method is tested on model solutions and intermetallics. The method provides a high enrichment factor, a wide concentration range of Yb determination (12.5-1000 ng·mL -1 ).