This diploma thesis deals with an optimization technique for the determination of semimetals in selected samples of food, which consists of sample digestion, preconcentration and detection of the elements. Preconcentration is usually chosen because these elements are contained in foods only in trace amounts, which are undetectable for some techniques. This work also made characteristics of semimetals, in terms of their functions in the body, of the occurrence in food and the consequences for the organism on their surplus or shortage. The chosen technique of preconcentration in this work was the preconcentration of titanium dioxide. When optimizing the techniques, however, was unlike the results published in literature, obtained low yield of elements sorbed on titanium dioxide, therefore the samples were measured by inductively coupled plasma mass spectrometry directly after their mineralization, wet digestion with low temperature. The results of this work indicate that the elements arsenic, boron and selenium are given technique detectable without preconcentration, whilst set germanium content in all samples failed, due to very low concentrations and therefore in these cases would be required preconcentration.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has risen to among the top tier techniques for the direct analysis of solid samples. However, significant problems remain that must be solved to achieve the full analytical potential of LA-ICP-MS. Inefficient conversion of aerosol to ions within the ICP or transmission through the MS interface may decrease precision, sensitivity, and/or accuracy. Although fundamental mechanisms that govern ion production and transmission have been studied extensively in solution-nebulization (SN) ICP-MS instruments, significant gaps in our understanding remain. Furthermore, it is unclear to what extent differences between the aerosols generated during SN and LA influence either ion production or transmission. In this work, I initially investigated differences in the spatial distributions of Ca, Ba, and Sc ions generated by LA and SN using high-resolution LIF imaging. Ions formed from aerosol generated by LA at low fluence were distributed over much greater axial and narrower radial distances than SN aerosol. Additionally, I investigated the effects of solvent, laser fluence, and ablation atmosphere (He vs Ar) on ion distributions in the ICP. Unlike solvent, changing laser fluence and ablation atmosphere produced considerable changes in the ion signal intensity and spatial distribution during LA. At greater laser fluence, the radial distance over which ions were distributed dramatically increased. Surprisingly, when helium was mixed with argon as carrier gas, ion signals decreased. Many of these effects were assumed to be related to changes in the number and size of particles generated during LA. In a follow-up study, relative contributions to ion densities in the ICP from particles of different sizes were investigated. LIF images were recorded while filtering particles above a threshold size on-line. Micron-sized particles contributed the majority of ions formed in the ICP. For Ba, Ca, and Sc, differences in the axial position where nanometer- and micron-sized particles vaporized were 2, 1, and less than 1 mm, respectively. I also performed experiments to identify changes in the ion signal related to changing ablation conditions vs. changing ICP conditions associated with helium additions to the carrier gas. LIF images were recorded during different combinations of He/Ar added upstream and/or downstream of the ablation cell. Changes in the ion signal during ablation in helium vs argon did not always match expectations based on changes in particle numbers and sizes measured with SEM. The results force re-examination of some of the fundamental assumptions about the effect of carrier gas composition on the performance of LA-ICP-MS. The research described in this dissertation provides valuable insight into fundamental aspects of key ICP processes related to LA generated aerosol.

No description available.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this work a robust reversed phase ion-pairing high performance liquid chromatographic (RP-HPLC) method has been developed for the separation, characterization and quantification of all possible [PtCl6-nBrn]2- (n = 0 – 6) and [PtCl4-nBrn]2- (n = 0 – 4) complex anions using UV-Vis detection. High resolution 195Pt NMR of more concentrated PtII/IV solutions served to validate the relevant species assignments, particularly those of the stereoisomer species, cis- and trans- [PtCl4Br2]2-, [PtCl2Br4]2- and mer- and fac-[PtCl3Br3]2-. Quantification of the PtII/IV species was achieved by means of IP-RP-HPLC coupled to either ICP-MS or ICP-OES, and together with the UV-Vis absorption spectra obtained by photodiode array (PDA) recording of all eluted species, allowed for the determination of the photometric characteristics (λmax and ε) of all the PtII/IV species. This data enables practical speciation studies of such PtII/IV complex anions using standard analytical equipment. The hyphenation of ion-pairing RP-HPLC to ICP-OES allows for the successful determination of the Pt to halide mole ratios of individually separated species in order to characterize these species in a novel manner. The Pt to chloride and/or Pt to bromide mole ratio of the [PtCl4]2- and the series of [PtCl6-nBrn]2- (n = 0 – 6) complexes were determined using HPLC-ICP-OES based on the 177.708 nm Pt, 134.724 nm Cl and 148.845 nm Br emission lines and served as a technique for the unambiguous chemical speciation of such complexes. An increase in sensitivity of the developed method was achieved by the use of an ion-pairing reversed phase ultra high performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (UHPLC-ESI-Q-TOF-MS) method. This method proved capable of separating and characterizing the homoleptic and heteroleptic [PtIVCl6-nBrn]2- (n = 0 – 6) and mono-aquated [PtIVCl5-nBrn(H2O)]- (n = 0 – 5) complex anions in well defined acidic aqueous solutions. Ion-pairing ultra high performance liquid chromatography separation based on the volatile ion-pairing reagent, tributylamine, provided adequate chromatographic resolution as well as sufficiently low background noise for high resolution ESI-Q-TOF-MS detection. The wealth of structural information contained in the mass spectra obtained for each PtIV species simplified the identification of individual species. Moreover, the general fragmentation trends encompassing a constant incremental change of 44 Da (79/81Br - 35/37Cl) resulting from the successive substitution of Cl- by Br-, in combination with the observed elution order, facilitated the relevant species assignments. The developed method enabled the relative rapid (<13 min) characterization of all 22 [PtCl6-nBrn]2- (n = 0 – 6) and mono-aquated [PtCl5-nBrn(H2O)]- (n = 0 – 5) species. Quantification of each individual [PtCl6-nBrn]2- (n = 0 – 6) species by means of ion-paring HPLC-UV-Vis allowed for the determination of all 17 stability constants for the PtIV chloridobromido halide exchange reaction network. Determination of the associated Gibbs free energies for each ligand exchange reaction step, o rxnK ΔG n (n = 1 - 17), together with energy conservation relationships, served to validate the accuracy of the experimentally calculated stability constants. The experimentally determined overall formation constant, or ΔGo rxn, and those calculated using the standard reaction half cell reduction potentials of [PtCl6]2- and [PtBr6]2- were in good agreement, further confirming the experimentally obtained thermodynamic parameters. The thermodynamic driving force for the PtIV chloride-bromido exchange reactions is attributed to the hydration of the halide ligands, which drives the reaction towards the bromido PtIV species in aqueous solutions, even though the chlorido PtIV complexes are energetically favoured in this reaction network. Evaluation of other metal cation halido exchange reactions shows that all metal halido complexes exhibit the F- >> Cl- > Br- > I- order of thermodynamic stability and is only inverted due to the solvation of the relevant halide ligands. Furthermore, density functional theory (DFT) was used to predict the thermodynamic stabilities with respect to the isodesmic reactions involving chlorido-bromido PtIV stereoisomer pairs and chlorido-bromido PtIV ligand exchange reactions of the [PtCl6-nBrn]2- (n = 0 – 6) species and confirm the F- >> Cl- > Br- > I- order of thermodynamic stability as well as determining the ΔΔGo rxn within the range of 8 - 20 kJ.mol-1 to the experimentally determined ΔΔGo rxn. / AFRIKAANSE OPSOMMING: Tydens hierdie studie is „n robuuste “reverse-phase” ioonparing hoë-verrigting vloeistof chromatografie, RP-IP-HPLC, metode ontwikkel vir die skeiding, karakterisering en kwantifisering van alle moontlike [PtCl6-nBrn]2- (n = 0 – 6) en [PtCl4-nBrn]2- (n = 0 – 4) kompleks anione waar UV-Vis as detektor gebruik word. Die relavante spesies toedelings wat gemaak is, veral ten opsigte van die cis- en trans-[PtCl4Br2]2-, [PtCl2Br4]2- en mer- en fac-[PtCl3Br3]2- stereo-isomeerpare, is deur middel van hoë-resolusie 195Pt KMR van meer gekonsentreerde PtII/IV oplossings bevestig. Die PtII/IV spesies was gekwantifiseer deur die IP-RP-HPLC aan of „n ICPMS of „n ICP-OES te koppel. Daarenbowe was dit moontlik om die fotometriese eienskappe (λmax en ε) van elke individuele PtII/IV komplex anion te bepaal deur die UV-Vis absorpsie spektrum van elke elueerende spesies met PDA op te neem. Die nuwe metode wat tydens hierdie studie ontwikkel is het dit dus moontlik gemaak om sulke PtII/IV komplek sanione met standaard analitiese toerusting prakties te skei. Verder is gevind dat deur IP-RP-HPLC aan ICP-OES te koppel dit moontlik is om die Pt tot halied mol verhoudings van elke individueel geskeide spesies te bepaal en dus hierdie spesies op „n oorspronklike, nuwe manier te karakteriseer. Die Pt tot chloried en/of Pt tot bromied mol verhoudings van die [PtCl4]2- en die reeks van [PtCl6-nBrn]2- (n = 0 – 6) kompleks anione, soos bepaal deur gebruik te maak van HPLC-ICP-OES, is gebasseer op die 177.708 nm Pt, 134.724 nm Cl en 148.845 nm Br emissie lyne. Hierdie metode kan gebruik word vir die eenduidige chemiese skeiding van hierdie komplekse. Die sensitiwiteit van hierdie metode was egter verder verbeter deur gebruik te maak van ioonparing “reverse-phase” ultra hoë-verrigting vloeistof chromatografie gekoppel met elektrosprei ionisasie quadropool “time-of-flight” massa spektrometrie (UHPLC-ESI-Q-TOFMS). Deur dit te doen is dit nou selfs moontlik om die homoleptiese en heteroleptiese [PtIVCl6-nBrn]2- (n = 0 – 6) spesies, asook die “mono-aqauted” [PtIVCl5-nBrnH2O]- (n = 0 – 5) spesies in „n goed gedefinieërde aangesuurde waterige oplossings te skei en te karakteriseer. Die vlugtige ioon-paringsreagent, tributielamien, is vir die skeidingsproses op die IP-UHPLC gebruik om te verseker dat voldoende chromatografiese resolusie, so wel as lae genoeg agtergrondgeraas, verkry word vir hoë-resolusie ESI-Q-TOF-MS deteksie. Die rykdom informasie vervat in die massaspektrum van elke PtIV spesies het die indentifikasie van elke spesies vergemaklik. Daarenbowe het die fragmentasie tendens, aanduidend van „n konstante inkrementele verandering van 44 amu (71/81Br – 35/37Cl) weens die opeenvolgende substitusie van Cl- met Br-, tesame met die elusie volgorde, die spesies-toedelings gefasiliteer. Met hierdie nuut ontwikkelde metode is dit nou moontlik om al 22 [PtCl6-nBrn]2- (n = 0 – 6) en “mono-aquated” [PtCl5-nBrnH2O]- (n = 0 – 5) spesies in „n relatiewe kort tydperk (< 13 min) te karakteriseer. Deurdat elke [PtCl6-nBrn]2- (n = 0 – 6) spesies nou individueel met IP-HPLC-UV-Vis gekwantifiseer kan word, is dit moontlik om al 17 stabiliteitskonstantes vir die PtIV chloridobromido halied uitruilingsreaksienetwerk te bepaal. Die geassosieerde Gibbs vrye energie, ΔG°rxnKn (n = 0 – 17), wat vir elke stap in die uitruilingsreaksienetwerk bepaal is, tesame met die energiebewaring verhoudings, was gebruik om die akkuraatheid van die eksperimenteel bepaalde stabiliteitskonstantes te bekragtig. Verdermeer was die waarde van die algehele formasie konstante wat eksperimenteel bepaal is, ΔG°rxn, in goeie ooreenstemming met dit wat bereken is deur die standaard reaksie halfsel reduksie potensiale van [PtCl6]2- en [PtBr6]2-. Dus is die eksperimenteel verkrygde termodinamiese parameters bevestig. Die termodinamiese dryfkrag vir die PtIV chloried-bromied uitruilingsreaksies is toegereken aan die hidrasie van die halied ligande, wat in waterige oplossings die reaksie na die bromied PtIV spesies dryf, al is die chloried PtIV spesies energeties bevoordeel in hierdie reaksienetwerk. Evaluering van ander metaalkatioon- halied-uitruilreaksies wys dat alle metaal-halied komplekse die F- >> Cl- > Br- > I- orde van termodinamiese stabiliteit volg en dat hierdie volgorde slegs omgekeer sal word weens solvasie van hierdie halied ligande. Darenbowe digtheids funksionele teorie (DFT) gebruik om die termodinamiese stabiliteit met betrekking tot isodesmiese reaksies wat chloried-bromied PtIV stereoisomeer pare behels te voorspel, sowel as van chloried-bromied PtIV liganduitruilingsreaksies van die [PtCl6-nBrn]2- (n = 0 – 6) spesies, en bevestig die F- >> Cl- > Br- > I- volgorde van termodinamiese stabiliteit. Verder was dit ook moontlik om met DFT die ΔΔG°rxn tot so naby as 8 – 20 kJ.mol-1 te bereken.

Les déchets solides générés par notre société sont nombreux. Les cendres volantes sont des déchets solides produits lors de la combustion de déchets domestiques ou industriels dans des incinérateurs. Les cendres volantes sont également produites par la combustion du charbon dans les centrales à charbon. Les cendres volantes sont des résultats de ces combustions et représentent importante quantité de déchets produits chaque année par notre société. Les possibilités de recyclage de ces déchets sont nombreuses : dans la construction, l'industrie routière. Elles sont également stockées pour une utilisation ultérieure. Les origines différentes des charbons et déchets incinérés conduisent à une minéralogie et une composition élémentaire complexe. En tant que sous-produit le devenir des cendres volantes est important à déterminer, aussi la détermination de la composition élémentaire de ces cendres volantes est-elle indispensable.Les méthodes classiques de préparation des échantillons solides sont la minéralisation acide ou la fusion alcaline. Ces procédures prennent du temps et supposent l’utilisation de réactif, de plus la digestion complète n'est pas toujours assurée. Le risque de contamination par les réactifs employés est important au cours de ces méthodes classiques de préparation. Au cours de la dernière décennie, le développement d’analyse directe d'échantillons solides en utilisant des méthodes d'ablation laser a été important en raison de la nécessité de réduire le temps d'analyse et de réduire aussi la consommation de réactifs. Dans ce travail, deux méthodes basées sur l'ablation par laser seront étudiées pour l'analyse des cendres: Laser Induced Breakdown Spectroscopy (LIBS) et Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). La spectrométrie LIBS sera étudiée pour la détermination quantitative des éléments majeurs dans les échantillons de cendres alors que le couplage ablation laser ICP / MS sera employé pour détermination des éléments traces. L'optimisation de la sensibilité et les stratégies d'étalonnage sont les principaux problèmes traités dans ce travail. La préparation des échantillons et l’optimisation ont été effectuées pour déterminer les éléments tels que Al, As, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Sr, V et Zn par les deux méthodes.Les performances analytiques telles que les limites de détection, justesse ont été obtenus à la suite d'optimisations appropriées des liants et de la sélection de l’étalon interne approprié. En conclusion, l’analyse directe de solides en utilisant les techniques basées sur l’ablation laser développées dans ce travail conduisent à une justesse acceptable pour la détermination des éléments majeurs et traces dans les cendres volantes / Solid waste generated by our society are numerous, fly ashes are produced during the combustion of domestic or industrial waste in incinerators. Fly ashes are also produced through coal combustion in coal fired power plants. Fly ashes are results of these combustions and represent important quantity of waste produced every year by our society. They have variable use – in construction, road industry, or they can be stocked for further use. As they are result of different origin, they have complex mineral and elemental composition. As a by-product or as a recycled product fly ashes fate is important to determine. In this view the determination of the elemental composition of fly ashes is the aim of this work.Conventional methods of sample preparation are acid digestion or alkali fusion. These procedures are time and reagent consuming and complete digestion is not assured. The potential contamination of the reagents employed is important during these classical sample preparation methods. During the past decade, development of direct solid sampling using laser ablation methods was important due to the need of reducing analysis time and also reducing reagent consumption. In this work, two methods based on laser ablation will be studied for fly ash analysis: Laser Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). LIBS will be studied for quantitative determination of major elements in fly ash samples while Laser ablation / ICP MS will be employed for trace element determination.The sensitivity optimization and different calibration strategies are key problems of laser sampling methods. Sample preparation and condition optimisation were performed to determine major, minor and trace elements such as Al, As, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Sr, V and Zn by both methods – LIBS for major elements and LA-ICP-MS for minor and trace elements.Analytical properties such as detection limits, accuracy and analytical working curves were obtained following suitable optimisation of binders and internal standards. Compromise binder and analytical conditions were selected to determine the elements in fly ash samples.In conclusion, direct solid sampling using laser ablation followed by LIBS or for solid introduction into ICP was found to determine major, minor and trace elements in fly ashes, improving pellets mechanical stability, high samples sensitivity and acceptable accuracy and detection limits.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The determination of the platinum group metals (PGMs), platinum, palladium, rhodium, iridium, ruthenium and osmium, remains a problem for the low-grade ore samples, and the analysis of these samples in a routine laboratory relies entirely on the fire assay technique. The use of large sample masses to overcome sub-sampling errors has been the greatest advantage of this technique. The increased economic value of PGMs and recent developments in instrumentation such as inductively coupled plasma-mass spectrometry (ICP-MS) which is capable of trace element detection as low as part per billion (Ppb) levels, have led to a search for complementary methods to ensure the accuracy of fire assay results. This work investigates the feasibility of direct dissolution of ore samples using microwave-assisted dissolution followed by ICP-MS as the measurement technique. Due to the limited sample mass that can be used, a thorough consideration had to be given to sampling errors and analytical errors to assess the overall precision achievable. Most PGM-bearing minerals occur as sulphides and these are highly resistant to acid dissolution. It was found that roasting the Merensky type samples in air, prior to dissolution gives quantitative recoveries for platinum. Recoveries up to 100% were obtained for platinum, palladium, rhodium and gold for a Merensky flotation concentrate with excellent precision (about 4%) except for gold which had poorer precision (16%). However, ore samples presented a problem due to their lower PGM content and smaller sample masses being used. Precision for all elements improved significantly (from about 20% to about 8%), with the use of l g-sample aliquot compared to that ofO.25 g-sample. Acid dissolution, even after roasting proved to be insufficient for the UG-2 chromitite samples. When roasting was followed with reduction under hydrogen flame the solubility of the UG-2 flotation concentrate improved remarkably. The recoveries obtained were approximately 95 ± 5% for platinum, 99 ± 5% palladium, 104 ± 12% gold and 102 ± 5% for rhodium with good precision (comparable to that of Merensky concentrate). The accuracy and precision of the results depended very much on the sample mass and air-flow in the furnace during the roasting procedure. For this method to be used successfully, the air flow is very critical, and should lead to a better furnace design which can rotate the crucibles to enable an even flow of air over all the samples during roasting. / AFRIKAANSE OPSOMMING: Die bepaling van platinumgroep metale (PGM'e), platinum, palladium, rhodium, iridium, ruthenium en osmium is 'n voortdurende probleem vir die lae-graad erts monsters. Die analise van hierdie monsters in 'n roetine laboratorium is geheel afhanklik van die klassieke "fire assay"-tegnieke. Die groot voordeel van hierdie tegniek is die voorkoming van monsternemingsfoute deur die gebruik van groter monster massas. Die ekonomiese waarde van PGM'e saam met die onlangse ontwikkeling van instrumentasie soos die induktief-gekoppelde plasma-massaspektrometrie (IGP-MS) wat in staat is om spoorelemente in konsentrasies so laag soos dele per biljoen (ppb) te meet, het daartoe gelei na soeke vir komplementêre metodes om die akkuraatheid van klassieke "fire assay" -tegnieke te verseker. Hierdie werk ondersoek die waarskynlikheid van direkte oplossing van ertsmonsters deur gebruik te maak van mikrogolf-ondersteunde oplossing gevolg deur IGP-MS as opmetingstegniek. As gevolg van die beperkte monster massa wat gebruik kan word, moes deeglike oorweging gegee word aan monsternemingsfoute en analitiese foute, om die oorkoepelende presiesheid te bepaal. Meeste PGM-draende minerale bestaan in die vorm van sulfiede en bied groot weerstand teen oplossing in 'n suur. Die gloei van Merensky-tipe monsters in lug voor oplossing gee kwantitatiewe herwinning van platinum Herwinning tot 100% is behaal vir platinum, palladium, rhodium en goud vir 'n Merensky-flotasie-konsentraat met uitstekende akkuraatheid (4%) behalwe vir goud met 'n swak (16%) akkuraatheid. Die erts monsters was problematies as gevolg van die laer PGM inhoud en kleiner monstermassas wat gebruik is. Presiesheid vir al die elemente het beduidend verbeter (van 20% tot 8%) met die gebruik van 1 g- monster massas vergelyk met 0.25 g-monsters. Ten spyte van die gloei van die monster is suur oplossing onvoldoende vir die UG-2 chromatiet-houdende monsters. Wanneer die monster gegloei is onder 'n waterstof vlam (reduksie) het die oplossbaarheid van UG-2 flotasie-konsentraat aansienlik verbeter. Die herwinbaarheid wat behaal is, is 95 +/- 5% vir platinum, 99 +/- 5% vir palladium, 104 +/- 12% vir goud en 102 +/- 5% rhodium met goeie relatiewe presiesheid vergeleke met Merensky-konsentrate. Die akkuraatheid en presiesheid van resultate hang meerendeels af van monster massa en lugvloei in die oond gedurende gloei. Die lugvloei is krities vir die sukses van hierdie metode en sal moet lei tot beter oond ontwerp wat kroesies kan roteer en 'n gelyke vloei van lug oor die monsters gedurende verbranding toelaat.

L’objectif de cette thèse était la modélisation numérique de la torche à plasma à couplage inductive. (ICP). Nous avons établi les bases de données nécessaires : composition, propriétés thermodynamiques et de transport appliqués aux mélanges d’argon, d’acide nitrique et d’eau. Le modèle hydrodynamique de la torche ICP (7 spires) considère le plasma à l'équilibre thermodynamique et couple les équations de Navier-Stokes pour décrire l'écoulement du plasma aux équations de Maxwell pour décrire l'évolution du champ électrique et du champ magnétique. / The purpose of the work was the numerical modeling of the inductive coupling plasma torch. (ICP). We have established the necessary databases: composition, thermodynamic and transport properties applied to argon mixtures of nitric acid and water. The hydrodynamic model of the ICP torch (7 coils) considers the plasma at thermodynamic equilibrium and uses the Navier-Stokes equations to describe the plasma flow and the Maxwell equations to describe the evolution of the electric field and the magnetic field.

M.Sc. / The origin of a wine plays a key role in establishing the quality and the price the consumer is prepared to pay. Fingerprinting techniques based on multi-element data combined with multivariate statistical analysis as well as isotope ratio data for certain elements such as boron (11B/10B) and strontium (87Sr/86Sr) are being developed and have been used for provenance determination of wine with varying degrees of success. The aim of this study was to develop a method to determine boron isotope ratios (11B/10B) with the required precision using ICP-MS (inductively coupled plasma mass spectrometry) in soil and wine samples and applying this method to establish the origin of South African wines. Analytical difficulties such as the boron memory effect, dead time, mass bias drift and matrix effects were investigated. Although the memory effect, dead time and mass bias drift were satisfactorily resolved, it was not possible to determine what the cause of all the observed matrix effects was during this study. The method was used to categorise wines from the Robertson, Swartland and Stellenbosch regions and an attempt was made to link the measured boron isotope ratios with that obtained from the corresponding provenance soils. The 11B/10B isotope ratios for the wine samples (Robertson: 4.202 ± 0.014, Swartland: 4.173 ± 0.013 and Stellenbosch: 4.174 ± 0.028) were, however, higher than the ratios obtained for the soil samples (Robertson: 4.108 ± 0.020, Swartland: 4.070 ± 0.023 and Stellenbosch: 4.124 ± 0.039). It was possible to distinguish, using the boron isotope ratios (wine and soil samples), between the Robertson area (Breede River region) and the Swartland area (Coastal region). The wine and soil 11B/10B isotope ratios obtained for the Stellenbosch area (Coastal region) overlapped with the 11B/10B isotope ratios of the Robertson and Swartland regions making it impossible to differentiate it from these two regions.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Mercury (Hg) is an example of a toxic metal that is not essential for nutrition. It exists in organic and inorganic forms in seafood and vapour from dental amalgam fillings respectively. Elemental mercury (Hg0) from dental amalgam was the focus of this study. Dental amalgam is one of the most commonly used dental filling materials and has been used for over 150 years. It is composed of Hg0 (approximately 50%) combined with other metals such as copper and zinc (Zn). These fillings give off Hg0 vapour throughout their existence, and is further enhanced by activities such as chewing, grinding of teeth and drinking hot liquids. Mercury consumption can lead to Zn loss or deficiency, and is reported to displace Zn and copper. Several European nations have outlawed the use of amalgam as a restorative material due to controversies regarding its safety in children, women of childbearing age and individuals with renal disease. Moreover, various studies have reported correlations between the number of amalgam fillings and Hg concentration in blood plasma, urine, faeces, saliva and different organs. Blood, urine, and hair mercury levels are used to predict possible health effects that may be caused by the different forms of Hg. Urine Hg is used to test exposure to metallic Hg0 vapour and inorganic Hg forms. This study aimed to evaluate the effects of Hg0 from dental amalgam restorations on the status of Zn in the urine. This was done by determining the concentrations of Hg0 in urine, buccal cells and the oral cavity, and its relationship with urinary Zn concentrations in the same individuals. Samples of urine, buccal tissues, chewing gum and completed questionnaires were collected from the participants (women and men) at the dental clinics in Tygerberg Hospital (TBH), Cape Town. Samples were analyzed using inductively coupled plasma mass spectrometer (ICP-MS). Findings from this study show that there was a correlation between levels of urinary Hg0 and urinary Zn (p=0.02). However, urinary Hg0 did not predict the amount of urinary Zn. Also, no relationship was found between levels of Hg0 in buccal swab or the chew test samples and urinary Zn level. There was a significant difference between females and males in the level of urinary Zn, men had higher levels of Zn excreted in the urine than females (p=0.05). However, there was no significant difference in the level of urinary Hg0 between males and females. The number of fillings (4-7) and age of fillings were significantly associated with urinary Hg0 level (p˂0.05), while smoking ˃15 cigarettes/day increased the level of Hg0 in buccal swab samples (p=0.002). We were not able to demonstrate a causal effect of Hg0 leaching on urinary zinc levels.

The primary aim of this thesis is to develop image processing algorithms to quantitatively determine the link between traumatic brain injury (TBI) severity and chronic traumatic encephalopathy (CTE) neuropathology, specifically looking into the role of blood-brain barrier disruption following TBI. In order to causally investigate the relationship between the tau protein neurodegenerative disease CTE and TBI, mouse models of blast neurotrauma (BNT) and impact neurotrauma (INT) are investigated. First, a high-speed video tracking algorithm is developed based on K-means clustering, active contours and Kalman filtering to comparatively study the head kinematics in blast and impact experiments. Then, to compare BNT and INT neuropathology, methods for quantitative analysis of macroscopic optical images and fluorescent images are described. The secondary aim of this thesis focuses on developing methods for a novel application of metallomic imaging mass spectrometry (MIMS) to biological tissue. Unlike traditional modalities used to assess neuropathology, that suffer from limited sensitivity and analytical capacity, MIMS uses a mass spectrometer -- an analytical instrument for measuring elements and isotopes with high dynamic range, sensitivity and specificity -- as the imaging sensor to generate spatial maps with spectral (vector-valued) data per pixel. Given the vector nature of MIMS data, a unique end-to-end processing pipeline is designed to support data acquisition, visualization and interpretation. A novel multi-modal and multi-channel image registration (MMMCIR) method using multi-variate mutual information as a similarity metric is developed in order to establish correspondence between two images of arbitrary modality. The MMMCIR method is then used to automatically segment MIMS images of the mouse brain and systematically evaluate the levels of relevant elements and isotopes after experimental closed-head impact injury on the impact side (ipsilateral) and opposing side (contralateral) of the brain. This method quantifiably confirms observed differences in gadolinium levels for a cohort of images. Finally, MIMS images of human lacrimal sac biopsy samples are used for preliminary clinicopathological assessments, supporting the utility of the unique insights MIMS provides by correlating areas of inflammation to areas of elevated toxic metals. The image processing methods developed in this work demonstrate the significant capabilities of MIMS and its role in enhancing our understanding of the underlying pathological mechanisms of TBI and other medical conditions. / 2019-07-09T00:00:00Z