Molecular and atomic spectrometric determination of traces of lanthanides.

Abstract

Trace characterization of individual lanthanides in complex real samples is gaining importance in view of the high value applications such as lasers, phosphors, magnetic bubble memory films, super conductors etc. An extensive literature survey since 1980 on the analysis of metallurgical, geological, environmental and high purity materials for quantification of rare earth elements has been carried out and compiled in Chapter 1. Spectrophotometric, spectrofluorimetric and flame atomic absorption spectrometric techniques were chosen in the present study compared to widely used WDXRF, ICP-AES and ICP-MS in view of the advantages such as low cost, rapid analysis, ready availability(being present in all laboratories) and easier interpretation.

Chapter 2 describes about a spectrofluorimetric procedure for erbium based on the quenching of fluorescence of Rhodamine 6G(a xanthate dye) on formation of ternary ion association complex: erbium – 5,7-dichloroquinoline-8-ol Rhodamine 6G. This procedure was applied to the determination of total rare earth element (REE) content in seawater as other lanthanides also behave similarly. Various parameters that influence this determination were systematically optimized and the results obtained are discussed in this chapter.

Chapter 3 deals with the luminescence procedure for europium based on the formation of multicomponent complex: Eu(III) – thenoyltrifluoroacetone(TTA) – Tri-n-octyl phosphine oxide (TOPO) in presence of Terbium and finds application for the determination of traces of europium in high purity Y2O3 and Gd2O3.

Analytical techniques chosen in the present study have some disadvantages such as, not sensitive and selective enough for a particular lanthanide ion. Hence, a number of preconcentration and/or separation methodologies have been employed in conjunction with various analytical techniques. Of these, Solid phase extraction (SPE) has come to the forefront in the last 2-3 years. SPE preconcentration procedures developed for REE in the past have been critically discussed in chapter 4.

Chapter 5 concerns with a new SPE preconcentrative separation procedure for dysprosium using ion imprinted polymer (IIP) particles by copolymerization of styrene monomer and a cross linking agent divinyl benzene in the presence of Dy(III) – 5,7-dichloroquinoline-8-ol – 4-vinyl pyridine ternary complex where in DY(III) ion is the imprint ion. Selectivity coefficients for dysprosium with respect to other lanthanides were then compared with the reported separation factors using well known and commercially employed liquid – liquid extractants such as D2EHPA & EHEHPA.

The post γ-irradiation of dysprosium IIP particles, resulted in enhancement of selectivity coefficients for dysprosium with respect to other lanthanides & yttrium when compared to non-irradiated dysprosium IIP particles. The preparation and characterization of post γ-irradiated and unirradiated dysprosium IIP particles were described in chapter 6.

Chapter 7 discusses about a multielement SPE preconcentration procedure for neodymium, europium and lutetium using 5,7-dichloroquinoline-8-ol modified microcrystalline naphthalene and subsequent determination by FAAS/ICPMS. The preconcentration procedure in conjunction with ICP-MS was applied to the determination of neodymium, europium and lutetium in sea water. The overall conclusions and future outlook based on the results obtained in the present investigation were highlighted in Chapter 8