Abstract
M.Tech.
The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique showed
very high uncertainties associated with the determination of the concentrations of
minor elements in the Platinum Group Metal (PGM) smelting plant samples. This
project reports on the work done for the identification of, and subsequent
minimisation of the sources of uncertainties associated with the measurements of
minor elements in the PGM Furnace Matte material by ICP-MS.
To perform these studies, Elan 6000, Shimadzu ICPM-8500 and Finnigan Element
2 ICP-M spectrometers were employed. Synthetic Furnace Matte samples
(SFMSs) were prepared and used to ascertain the uncertainties associated with
the alleged sources at Mintek and Leo-Tech laboratories.
The Element 2 spectrometer dominated the other two ICP-M spectrometers in
terms of the accuracy for the determination of the concentrations of minor
elements in SFMSs. The evidence of spectral interferences from the significant
deviations in the measurement results between the isotopes of the same element
was observed in the quantification of Zn, Se, Te and Sn in SFMS by the
quadrupole Elan 6000 and the Shimadzu spectrometers. It also transpired that the
accuracy of the quantitative determination of minor elements in the Furnace Matte
(FM) matrix by ICP-MS was hampered by the matrix elements with the severity
depending on the specific analyte and the make and model of the ICP-M
spectrometer. The Anglo platinum FM material that was analysed in the second
round robin was used as a Certified Reference Material (CRM) in the analysis of
the Lonmin FM sample. It was revealed that the laboratory standard operating
procedures for the preparation, dilution and subsequent analysis of the sample are
potential sources of uncertainty in measurement results. The two-fold dilution of
the sample for the lessening of the matrix effects was not effective. The use of
multi-walled nanotubes for the alleviation of the matrix effects by removal was also
not successful. Nevertheless standard addition method (SAM), combined with
internal standardisation can be used as an effective calibration method in ICP-MS
to achieve less matrix interfered results over the combination of the common
external standardisation and internal standardisation methods.