Use of organic reagents for the voltammetric determination of rare-earth elements

Abstract

Study of the properties of rare-earth elements (REEs) and their alloys and compounds is important from the viewpoints of both practice and theory, because these elements, by virtue of their valuable properties, are widely used in state-of-the-art technologies. Rare-earth elements show considerable promise for metallurgy, machine building, instrument making, the glass industry, and medicine [1]. Rare-earth silicides and germanides are used in the reactor-building industry. The relative thermal stability of REE along with their large activation cross-sections for neutron capture allows them to be used as neutron-absorbing materials for different units. Rare-earth elements enter into the composition of scintillation materials as activators. The characteristics of these materials significantly depend on the concentrations of REEs; therefore, reliable, sensitive, selective, and rapid procedures are required for their quality control. Rare-earth elements are most often determined by atomic emission spectrometry, which allows impurities of individual lanthanides to be determined in the presence of others. Luminescence and spectrophotometry are also often used. These methods are sensitive and selective, but they often require unavailable and specific reagents. Voltammetric methods are competitive with the above methods and, at the same time, possess important advantages, such as the high sensitivity and reproducibility of the results, rapidity, the possibility of the simultaneous determination of several components, and the availability of equipment [2].The reduction of REE(III) ions, especially Eu(III) and Yb(III), has been studied quite well [3]. There is information on the effect of pH and the supporting electrolyte; the kinetics of the Eu(III) Eu(II) and Yb(III) Yb(II) conversions was studied in [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Eu(III) and Yb(III) can be determined at a dropping mercury electrode (d.m.e) in the presence of other REEs [11][12][13][19][20][21][22][23][24][25][26]. The studies of Eu(III) reduction in aqueous-organic and organic media showed that these media were unsuitable for determining europium(III) because of their low conductivities [27][28][29][30].The REE(III) ions are reduced in the potential range from -1.7 to -2.0 V. There is no unified opinion about the nature of their polarographic waves; different assumptions were made in [31-41]. These waves (or peaks) are obtained at the potentials close to the potentials of the supporting electrolyte reduction and, therefore, are poorly selective. REE(III) can be determined by the proposed procedures only after the electrochemical or chemical separation of foreign REE(III) and Al(III), Cd(II), Co(II), Cu(II), Ni(II), Pb(II), Zn(II), and other ions [33,[42][43][44][45][46]. Therefore, voltammetry in conventional supporting electrolytes offers no advantages over other methods and is rarely used.At present, more than 30 organic ligands have been proposed for the voltammetric determination of individual or combined REEs. The selectivit...

Characterizing and Diminishing Autofluorescence in Formalin-fixed Paraffin-embedded Human Respiratory Tissue

“…If so, then EBT or modified EBT absorbs the autofluorescence emission, thereby reducing its intensity, then emits at the higher wavelength. The divalent metal-complexed red form, which absorbs at a lower wavelength than the blue form, is more likely to be the absorbing species (Dubenskaya and Levitskaya 1999). AR may expose epitopes for EBT binding, thereby producing a new fluorescent species.…”

Voltammetric Reduction of In(III)-Eriochrome Red B Complexes

“…The reduction of indium(III)-ERB complex completely correlates with the reduction of complexes formed by rare-earth metals(III) and this dye, which we studied previously [9][10][11]18], and with the reduction of indium(III) complexes of other dyes. We believe that, in this case, the ligand orbitals made a determining contribution to the lowest unoccupied molecular orbital of the indium(III)-ERB complex.…”

“…

Complexes of o , o '-substituted azo compounds are used for the voltammetric (VA) determination of Al(III) [1][2][3], Ga and In(III) [3], U(IV) [4], Zr(IV) [5,6], rareearth metals(III) [7][8][9][10][11], etc. In the majority of cases, an additional peak that corresponds to the reduction of a complex appears in the voltammograms.

…”

Rare Elements Electrochemistry: The Development of a Novel Electrochemical Sensor for the Rapid Detection of Europium in Environmental Samples Using Gold Electrode Modified with 2-pyridinol-1-oxide

“…The current analytical methods employed to analyze the lanthanides are generally: inter alia, 1,5 flame or graphite furnace atomic absorption spectrometry, [5][6][7] atomic absorption with chemical vapour generation, 5,[7][8] X-ray fluorescence spectrometry, 5,[7][8] inductively coupled plasma optical emission spectrometry, 5,[9][10][11] inductively coupled plasma mass spectrometry 5,10,12 and neutron activation analysis. 5,10,13 However, many of these methods require several time-consuming manipulation steps, sophisticated instruments and special training.…”