Development of measurement procedures for rapid analysis of major, rare earth and platinum group elements in geological materials

Syed Nadeem Hussain Bokhari

Research output: ThesisDoctoral Thesis

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Abstract

Rapid and effective measurement procedures are required in geological, industrial and environmental science for reliable information on chemical composition of unknown samples. Sample preparation is arguably the most important and primary step in exploration of whole rock chemistry in geochemical analysis. Geological materials comprising complex matrices and nature of refractory minerals like zircon and chromite pose problems in complete digestion. For the release of critical analytes contained in these mineral phases into the solutions, acids digestions combined with hazardous HF acid or alkali fusion are required. Use of HF acid has safety concerns and alkali fusions results in high salt contents which are problematic when analysed with ICP-MS. A classical sample digestion technique namely sodium peroxide sintering is developed and optimised for the evaluation of whole rock chemistry including rare earth elements (REEs) and platinum group elements (PGEs) in geological reference materials. Sintering ensures complete release of all the critical analytes into the solution and thus can be combined with various techniques. The complexity of the matrix elements in rendering spectral overlaps in ICP-MS spectrum for the mass fraction determination of analytes is a well-known problem. New methods for the mass fraction determination of major, trace and PGE including Ag and Au are developed using new collision reaction cell in combination with MS/MS technology in geological reference materials. Sintering is combined with isotope dilution mass spectrometry and tellurium co-precipitation and an improved method is developed for trace PGE mass fraction determination. Sintering is combined with isotope dilution mass spectrometry and anion exchange chromatography and discrepancies in mass fractions of Ru and Re in basalts are addressed again. The method developed abolishes the use of HF acid for Ru and Re mass fraction in basalts. Sintering enables ruthenium release into the solution hosted in silicate portions of the rock. The measurement principal for ruthenium sparging is innovated on the sinter solutions. In addition, two new methods for ruthenium distillation from sinter solution using (condensed phosphoric acid/K2Cr2O7 + concentrated HCl trap) and (KBrO3/chilled sulphuric acid trap) are developed. Ruthenium sparging and distillation are applied in two new reference materials (MUH-1 and OKUM) for the quantification of ruthenium mass fractions. The capabilities of cloud point extraction are evaluated on sinter solutions for matrix removal and pre-concentration of PGE. This combination does not offer good basis for PGE mass fraction determination. The capabilities of two new resins Diphonix® and CL for removal of matrix elements have been tested on sinter solutions. Although Diphonix® offers good analyte/matrix separation, it cannot be applied on the sinter solution due to chemistry of PGE ions. Retention abilities of PGE ions on Ag loaded CL resin are excellent but elution is still problematic. The method developed for sample digestion is applied on industrial and geological samples in collaboration with the University of Isfahan, Iran and the University of Bologna Italy for major and trace element determinations. The method developed with collision reaction cell has been applied on environmental samples for trace PGE mass fraction determination in collaboration with the University of Oulu Finland.
Translated title of the contributionEntwicklung von Messmethoden zur schnellen Analyse von Hauptgruppen-, Seltenerd- und Platingruppenelementen in geologischen Materialien
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Meisel, Thomas, Assessor A (internal)
  • Limbeck, Andreas, Assessor B (external), External person
Publication statusPublished - 2016

Bibliographical note

embargoed until null

Keywords

  • Reference materials
  • Collision reaction cell
  • Sample digestion
  • Refractory minerals
  • ICP-MS/MS
  • Sparging
  • Distillation
  • Platinum group elements
  • Rare earth elements

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