M.Sc. / Emulsions are not widely used in industry for wear-metal-in-oil determinations and this study was undertaken in order to evaluate such a possibility. The use of emulsified standards was compared to aqueous standards for the calibration of an emulsified used lubricating oil sample. The traditionally used methods of ashing in a muffle furnace and dilution with the organic solvent, xylene were also evaluated in comparison with the emulsion methodology. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the wear-metal-in-oil analysis. The performance characteristics of each method were compared for the following metals: AI, Cr, Cu, Fe, Ni, and Pb. The used oil sample and emulsified standards were acid treated and emulsified in water {1% wlw) using tetralin as solvent and triton X-100 as surfactant. This evaluation included the calibration characteristics, precision and accuracy obtained, as well as the results of recovery studies. The emulsification method was found to be comparable to the ashing and dilution methods in terms of calibration and only Cr, Cu, Fe and Pb concentrations were found. The precision of the emulsification method was found, in general, to be close to or less than 2% RSD. The used oil matrix also contained leaked petroleum from a problem car engine. An accurate determination of lead was consequently impossible since the high lead content led to sedimentation. The use of the internal standard, indium, was evaluated for its effectiveness in correcting possible matrix effects that were evident from the results obtained in the recovery studies. The recovery studies showed the Cr and Pb determinations to be adversely affected by internal standardization. An alternative approach for matrix effect correction, the common analyte internal standardization (CAIS) method was also investigated. This method held promise for allowing the use of aqueous standards, instead of oil or emulsion standards, for the calibration of the emulsified oil samples. Three different applications of the CAIS technique were investigated and all proved unsuccessful.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:2137 |
| Date | 05 March 2012 |
| Creators | Krusberski, Nicolle Birgit |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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