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A thesis submitted to the faculty of science, university of the Witwatersrand, Johannesburg,in fulfilment of the requirements for the degree of Doctor of Philosophy, 1994 / Alternative sample manipulation and sample introduction methods for inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS) have been investigated. The broad objectives of the study were to broaden the scope and improve the analytical performance of the techniques. The methods which were investigated were: 1) Laser ablation. This technique was used only in combination with ICP-MS. The technique was not applied to ICP-MS because the laser ablation system is dedicated to the ICP-MS instrument. The laser ablation system was applied to the direct analysis of solid refractory materials, without dissolution of the sample. The main advantages of avoiding the dissolution step are that the sample preparation is rapid, there is no dilution or contamination of the sample, and no loss of volatile analyte elements. The problems which were encountered with the use of laser ablation were firstly, poor precision of measurement relative to solution analysis due to sample particles of widely varying size entering the plasma, and secondly, memory effects when changing from one sample type to another. 2) Flow injection. This sample manipulation method was used in combination with pneumatic nebulization for ICP-AES and ICP-MS. The technique was applied to a number of different analytical problems, with the objectives of speeding up analysis times, increasing the matrix tolerance of the instruments, and automating a variety of sample preparation processes. 3) Hydride generation. This technique was applied to the determination of arsenic and selenium by ICP-AES and ICP-MS, using a novel type of gas, liquid separator. The advantages of the technique were the separation of the analyte elements from interfering matrix species, and increased analyte sensitivity due to the excellent transport efficiency of hydride generation relative to solution nebulization. Numerous advantages have been obtained from the application of these sample manipulation and sample introduction techniques. Methods have been developed for the analysis of materials which are not suited to conventional solution nebulization, and the techniques have been used to improve the efficiency of analysis, to achieve lower detection eliminate, and to eliminate interferences. / GR2017

M. Tech. Chemistry. / Methods developed for the analysis of used oil can play a vital role in monitoring the condition of engines and may help to improve overall equipment effectiveness. Quantification of trace elements in used lubricating oil forms a vital part in monitoring engine conditions and impact on the environment. The main objective of this work is to investigate methods used for the accurate determination of trace elements in lubricating oils. In this study, inductively coupled plasma-optical emission spectrometry (ICP-OES) was used for the determination of trace elements (Ag, Ba, Cu, Mn and Ni) in lubricating oils.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2005 / Keywords: ICP-OES, Chemometrics methods, internal standardization, matrix effects. Includes bibliographical references (leaves. 111-120).

Ph.D. (Chemistry) / The main objective of this study was to develop sample preparation methods based on separation and preconcentration of trace metals in organic matrices (alcohols, diesel and gasoline). The presence of metals in organic matrices is undesirable, unless they are used as additives. Therefore, it is important to control and monitor their concentrations in fuel and petrochemical products as they tend to affect the quality of these products. Solid phase extraction (SPE), solid phase microextraction (SPME) and hollow fiber-liquid phase microextraction (HF-LPME were used for separation and preconcentration of Ag, Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, V and Zn prior to their inductively coupled plasma optical emission/mass spectrometric (ICP OES/-MS) determination. For solid phase extraction, the exchange efficiencies of different commercial ion exchange resins, namely Dowex 50W-x8, Dowex 1-x8, Dowex MAC-3 and Chelex 100, for preconcentration of metal ions in alcohol and fuel samples, were investigated. The results obtained indicated that Dowex 50W-x8 was suitable for simultaneous preconcentration of cations such as Cd, Co, Ni, Cu, Fe, Mn and Zn, among other metals while Dowex 1-x8 was suitable for metal ions that exists in more than one oxidation states, namely, As, Cr, Mo, Sb and V. Chelex-100 and Dowex MAC-3 were found to be selective to a limited number of target metal analytes. For further applications, Dowex 50W-x8 and Dowex 1-x8 were employed. Furthermore, the applicability of synthetic adsorbents such as nanometer-sized alumina and functionalized cellulose nanofibers for preconcentration of trace metals in gasoline samples, was investigated. Nanometer-sized alumina sorbent was found to be suitable for simultaneous separation and preconcentration of Co, Cr, Mn, Ni and Ti. Functionalized cellulose nanofibers on the hand, were suitable for simultaneous preconcentration of Cd, Cu, Fe, Pb and Zn. The optimization of the experimental parameters was achieved by both univariate and multivariate procedure. The second preconcentration technique was solid phase microextraction which was also used for extraction and enrichment of metal ions in diesel samples using two approaches of the SPME method. The first approach was hollow fiber-solid phase microextraction (HF–SPME) method using fiber-supported sol-gel combined with a cation exchange resin (Dowex 50W-x8). This method showed satisfactory results for the preconcentration of Cd, Cu, Fe, Pb and Zn in diesel and gasoline samples. The second approach was based on membrane solid phase microextraction (MSPME) using titania-alumina hollow fiber. The MSPME method applied was used for extraction and preconcentration of trace amounts of Co, Cr, Mo, Ni, Sb and V in liquid fuel samples. Multivariate techniques were used for optimization of experimental parameters for both approaches. The last preconcentration technique that was developed was hollow fiber- liquid phase microextraction (HF-LPME). In this method fuel samples were first digested before being subjected to HF-LPME system. Ammonium pyrrolidine dithiocarbamate (APDC) and [C6MIM][PF6] ionic liquid were both used as chelating agent and acceptor phase, respectively. Two level factorial and central composite designs were used for multivariate optimization of experimental parameters. Satisfactory results were obtained for extraction and preconcentration of Ag, Al, As, Mn and Ti.

M.Sc. / The understanding of the classification and origin of geological systems is facilitated by the acquisition of accurate and precise analytical data. New instrumentation is rapidly developed for the preparation and quantitative analysis of geological materials using smaller amounts of sample, with lower limits of detection and faster analysis times. The development of new methodologies is crucial for the effective utilisation of new instrumentation. This study was conceptualised because of the relationship between the Department of Geology and the Central Analytical Facility of the Faculty of Science, University of Johannesburg. There is a high demand for accurate and precise chemical data for various lithologies and the availability of high-end analytical equipment, but little practical expertise to utilise this equipment to its full potential. The study is centred round the analysis of four common sedimentary lithological groups that are routinely studied by the Department of Geology namely carbonate rocks, shales, iron ore and manganese ore. A large literature base exists for the decomposition and analysis of geological materials. The bulk of this literature is centred round more established and conventional methods of sample preparation and analysis. The use of microwave digestion instrumentation and methodologies in recent times has revolutionised sample decomposition with shorter decomposition times, smaller sample masses required for decomposition, lower loss of analytes to volatilisation and creating a safer laboratory environment for analysts to work in. Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a more mature method of sample analysis, being commercialised in the mid 1970’s, while inductively coupled plasma mass spectroscopy (ICP-MS) is a newer technique, v being commercialised as of the mid 1980’s. These two techniques are multi-element techniques, with low limits of detection and fast analysis times for a plethora of analytes, over seventy elements for ICP-OES and over eighty elements for ICP-MS. Samples from all four lithological groups were successfully digested in a microwave digestion unit with varying combinations of nitric acid (HNO3), hydrochloric acid (HCl), perchloric acid (HClO4) and hydrofluoric acid (HF) and various digestion programs. Accurate and repeatable methods of analysis were developed for iron, manganese, calcium and potassium for all four lithologies with ICP-OES; aluminium was successfully determined for shale, iron and manganese ore with ICP-OES. Titanium, sodium, arsenic, barium, bismuth, chromium, copper, molybdenum, scandium, strontium and vanadium were determined for all four lithotypes with acceptable accuracy and repeatability using ICP-MS.

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.

In this thesis, new approaches to direct trace metals analysis of solid samples by inductively coupled plasma spectroscopy were investigated using laser ablation and thermal vaporization systems for solid sample introduction of biological, environmental, and pharmaceutical samples. / Laser ablation with inductively coupled plasma atomic emission spectroscopy (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) was applied to pharmaceutical tablets. Precision of analysis depended on laser parameters and could be improved using signal ratios. The feasibility of using laser ablation-ICP-MS for detecting natural levels of mercury along a single human hair strand was also demonstrated. / As well, the use of an induction-heating electrothermal vaporizer (IH-ETV) coupled to an ICP-MS was successful in determining mercury concentrations in a single human hair strand. Methodologies for multielement analysis of powdered hair were also explored using IH-ETV-ICP-MS. While calibration by reference hair materials showed promise, calibration methods by liquid standards were not suitable for any element. Detection limits achieved for most elements were below natural levels found in human hair. / IH-ETV-ICP-AES was also applied to the analysis of analyze-laden chromatographic powder. This study showed potential problems that may arise due to the methodology taken to analyze such materials. Finally, recommendations for future investigations and methodologies for laser ablation and thermal vaporization are discussed.

The Neolithic and late Iron Age pottery from the settlement site of Pool, Sanday, Orkney, was studied on two levels. Firstly, a morphological and technological study was carried out to establish a sequence for the site. Secondly an assessment was made of the usefulness of X-ray Fluorescence Analysis, Inductively Coupled Plasma Spectrometry and Petrological analysis to coarse ware studies, using the Pool assemblage as a case study. Recording of technological and typological attributes allowed three phases of Neolithic pottery to be identified. The earliest phase included sherds of Unstan Ware. This phase was followed by an assemblage characterised by pottery with incised decoration, which was stratified below a traditional Grooved Ware assemblage. The change in pottery styles and manufacturing methods with the Grooved Ware indicated that it evolved elsewhere. Grass tempered and burnished pottery characterised the Iron Age assemblage. Pottery samples from all phases of the site were analysed by XRF and ICPS. In addition, pottery from late Iron Age sites in the area was analysed for comparison with the Pool Iron Age pottery. XRF and ICPS analyses did not distinguish between either different phases at Pool or different Orcadian sites. This was attributed to the similarities in geological deposits over much of Orkney and the variations which can occur within a clay source. A clay survey was carried out in the vicinity of the site, and samples taken for comparison with the Pool pottery. Identification of rocks and minerals in thin section, and grain-size analysis, indicated that the Pool pottery was made locally to the site, and that both primary and secondary clays were used. It was concluded that petrological analysis is more suitable than elemental analysis in the study of coarse wares.

Thesis (M. Sc.)--University of Pretoria, 2004. / Title from opening screen (viewed 12th March, 2005). Includes summary. Includes bibliographical references.