Dissertations / Theses on the topic 'Platinum group analytical chemistry'

Centrifugal Partition Chromatography (CPC) is a multistage liquid-liquid countercurrent distribution technique which utilizes rotating teflon cartridges to hold a liquid phase stationary while the other liquid phase is pumped at a constant flow rate. It has been demonstrated to be a valuable technique for the base line separations of families of metal ions such as the platinum group metals (PGM)--Pt, Pd, Rh and Ir. The separations of these metals as their anionic chloro complexes were achieved using the heptane-water phase pair with a stable and relatively inexpensive extractant trioctylphosphine oxide (TOPO) functioning as a ligand in its neutral form and as a cation in its protonated form. A striking feature of the chromatograms of the complexes and ion pairs were their much poorer efficiencies compared to the efficiency of an organic analyte like 3-picoline under identical distribution rations. The inefficiencies of the PGM separations were also a function of the concentrations of the aqueous and organic phase components. These inefficiencies could be attributed to slow kinetics of the back extraction of the complexes and ion pairs and could be used to derive the mechanisms of these slow chemical kinetic steps. A correlation was established for the Pd(II) system between the CPC inefficiencies and the half lives of the slow reactions measured independently by stopped flow in micelles. This correlation was utilized to derive the rate constants for the back extraction of the TOPO complexes and ion pairs of Pt and Ir. The mechanisms of the extraction reactions were derived using the principle of microscopic reversibility based on the mechanisms of the back extraction reactions. This was then used to obtain estimates for the rate constants for the extraction reactions as well. The PGM were thus separated and their equilibrium and kinetics (extraction and back extraction) completely characterized using CPC. This is a significant development with CPC because such complete equilibrium and kinetic characterizations are hard to achieve with conventional liquid chromatographic techniques.

In this study, a reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed to separate and determine Pt and Pd after formation of their chelates with N,N-diethyl-N'
-benzoylthiourea (DEBT). With the aim of reducing the number of steps in treating the samples, the method developed does not require the elimination of excess chelating reagent before the analysis of metal chelates. The different physical and chemical parameters affecting separation were examined in details. The whole analysis was completed on a C18 column in 16 min at 280 nm, with the mobile phase of acetonitrile-methanol-water (80:10:10, v:v:v) containing 0.20 mol l-1 pH 5.0 acetate buffer at a flow rate of 0.8 ml min-1. Detection limits of the method, based on 3s, were found as 14.2 ug l-1 for Pd and 0.77 mg l-1 for Pt using a 20-ul sample loop. Reproducibility of the method for ten repeated measurements was found as 2.36 % for 0.60 mg l-1 Pd and 2.58 % for 10.0 mg l-1 Pt as % RSD. The proposed method is a rapid, simple and highly selective method for the simultaneous determination of Pt and Pd by HPLC without the need for any interference elimination process.

This Thesis describes the synthesis and characterisation of a variety of functionalised metal-organic frameworks (MOFs). These MOFs have been used for the extraction of platinum group metal (PGM) compounds from aqueous and organic solvents and for the storage of gases such as CO2, CH4 and the C2 hydrocarbons. Chapter 1 contains an introduction to PGM properties and uses with specific focus on the chemical properties which allow for separation of PGMs from base metal compounds and for separation between different PGM compounds. The synthesis and structure prediction of MOFs is then introduced, leading into an overview of the use of functionalised MOFs, especially those used for the encapsulation and extraction of metal ions from solution. General experimental techniques and details are described, as is the theory behind inductively coupled plasma optical emission spectrometry (ICP-OES), the most widely used analytical technique reported in this work. Chapter 2 describes the synthesis of chemically stable amine-functionalised Zr(IV) MOFs; UiO-68-NH2 and UiO-66-NH2, for extraction of PGM anions from aqueous and acidic solutions. ICP-OES was used to show that both materials exhibit close to 100% uptake of PtCl62- when present in just 3.5 equivalents per anion, comparable to the best materials reported for PtCl62- extraction. Furthermore, UiO-66-NH2 exhibited consistently higher PtCl62- uptake from aqueous solutions than four industrially used materials supplied by Johnson Matthey. Back-extraction of PtCl62- was demonstrated simply by heating the doped MOF in 4 M HCl, removing 99% of the PGM while maintaining the phase and crystallinity of UiO-66-NH2. Separation of PdCl62- from PtCl62- from acidic HCl solutions was exhibited by UiO-66-NH2, showing an exceptional selectivity of 20:1 for Pd:Pt from 2 M HCl. Likewise, 100% selectivity for PtCl62- and PdCl62- over CuCl2 and CuSO4 from acidic solutions was demonstrated, even in cases in which Cu was in 100-fold excess. Solid state NMR was employed to confirm the interaction between the framework and the PGM anions, with XPS results suggesting that the encapsulated Pt species within UiO-66-NH2 may be PtCl3(NH2)3 or PtCl4(NH2)2. Chapter 3 describes the synthesis and characterisation of a series of functionalised Cu(II) MOFs, NOTT-151, -155, -125 and -150, for the removal of neutral PGM complexes, Pd(OAc)2, PtCl4 and Rh2(OAc)4, from THF. The design of the MOFs allowed for an investigation into the effect of different topologies (ssa and fof), cage sizes and functional groups (amine, oxamide and methyl) on the uptake of each PGM complex. ICP-OES analysis showed that the MOFs were capable of extracting each PGM complex. The oxamide-functionalised NOTT-125 exhibited the most consistent uptake of Pd(OAc)2 with a maximum capacity of 35 mg g-1 (7 NH(CO)2NH groups per PtCl4). The amine-functionalised NOTT-155 showed the highest uptake of PtCl4, with a maximum capacity of 73 mg g-1 (4 NH2 groups per PtCl4). Uptake of Rh2(OAc)4 was generally low, however NOTT-125 showed a maximum extraction of 87 mg g-1 (3 NH(CO)2NH groups per PGM). The larger pore fof MOFs, NOTT-155 and NOTT-125, were more effective for each extraction than the MOFs of ssa topology, NOTT-151 and NOTT-150. However, of the ssa MOFs, amine-functionalised NOTT-151 was shown to give higher uptake of each PGM than the isostructural methyl-functionalised NOTT-150. This demonstrated the importance of incorporating a functional group capable of coordinating to the metal complex. Chapter 4 introduces the use of a nitrogen-rich triazine core in the synthesis of a variety of organic linkers to prepare MOFs for gas storage applications. The preparation of a novel 3,24-connected Cu(II) MOF of rht topology, denoted NOTT-160, is described and the structure characterised using X-ray crystallography. The material is shown to exhibit good uptake of C2 hydrocarbons with uptake of 128 cc g-1, 115 cc g-1, 110 cc g-1 for C2H2, C2H4, C2H6 respectively at 298 K and 1 bar (this becomes 212 cc g-1, 175 cc g-1 and 201 cc g-1 at 273 K and 1 bar). The selectivities of 79:1 and 70:1 calculated using Henry’s law for the separations of C2H2:CH4 and C2H4:CH4 respectively at 298 K are the third and second highest reported values for a MOF under these conditions. Ideal adsorbed solution theory (IAST) was also employed to calculate and predict these selectivities and shows agreement with the results obtained using Henry’s law. In addition, NOTT-160 shows an exceptional volumetric working capacity for CH4 of 221 cm3 cm-3 at 80 bar and 298 K. This is the second highest working capacity reported for a MOF under these conditions, with the excellent performance attributed to the high porosity and comparatively high crystal density of the material. Chapter 5 contains a summary of the work presented in this thesis.

Includes bibliographical references.
To date the principle methods for the determination of the platinum-group metals (PGMs) use an "off-line" assay with flame-atomic absorption spectrometry and visible spectrometry. Both suffer numerous interferences and involve time-consuming and arduous laboratory separation methods prior to analysis. An "on-line" method for the rapid assay of the PGMs is indeed a lacking component in the analysts' repertoire of methods. This study describes the development of spectrophotometric methods for the determination of the PGMs using flow-injection analysis (FIA). The principle of exploiting the remarkably specific and selective reaction of stannous halides with the PGMs to yield a series of intensely coloured complexes in acidic solutions forms the basis of these methods. The reaction is subject to relatively few interferences from other transition metals. A high speed scanning spectrophotometer is employed to obtain second order data. The successful manipulation of the data enables the determination of PGMs as single components and also simultaneously in mixtures. Attention is focused on the establishment of principles for successful multi-component analysis of PGMs. The development of a software program for multi-wavelength data manipulation was mandatory and is described. Criteria for successful selection of analytical wavelengths are discussed. The usefulness of multi-dimensional graphical data representation is demonstrated in a stop-flow study of the palladium reaction with tin (II) chloride. Qualitative information is provided regarding the nature of complexes and their interactions. Correlation of spectrophotometric data with complex solution colour changes is made. The requirements for future progress in multi-component FIA determinations as well as the direction for future research conclude the study.

Over the past few decades metals in medicine have played to play a significant role, especially after the discovery of the anticancer properties of cisplatin. However, acquired and intrinsic resistance, toxicity and a host of side-effects have encouraged the research for new metal based anticancer agents. Organometallic complexes have proved to be successful anticancer agents and several have commenced clinical trials. The aim of this study was to prepare and characterize trinuclear platinum group organometallic complexes and investigate their in vitro activity. The first series of ester containing complexes were prepared. The ligands were generated by the preparation of Schiff base ligands obtained from the condensation of 4-aminophenylmethanol and either benzaldehyde, 2-pyridinecarboxaldehyde or salicylaldehyde. Trimeric ester ligands were prepared from these monomeric ligands by reaction with trimesoyl chloride.

The structure and dynamics of ions and ion pairs in solution play an integral part in several biological and chemical processes. Historically the calculation of ion pair association constants from computer simulations has been complicated due to the difficulty in validating metal ion force fields for solution simulations. In this thesis a force field for divalent metal ions in metal sulfate solutions (i.e. Mg2+SO4 2-, Ca2+SO4 2-, Mn2+SO4 2-, Fe2+SO4 2-, Co2+SO4 2-, Ni2+SO4 2-, Cu2+SO4 2- and Zn2+SO4 2-) important in physical and biophysical experiments is produced. Potential of mean force calculations are used to provide ion pair free energy profiles and free energy perturbation calculations are used to calibrate the potential of mean force (PMF) from which association constants for ion pairs can be produced for these metal sulfate solutions. The calibrated free energy profiles result in calculated association constants that are in excellent agreement with available experimental data where available. Consequently the force field has been shown to be accurate for simulations of biophysical and physical systems. Furthermore the method, proposed in this thesis, for calibrating PMFs and calculating detailed association constants from those curves can most likely be used for complex systems that have previously been computationally inaccessible. Next a detailed account of solvation structures and the nature of ion pair formation mechanisms for important metal sulfates in aqueous media are presented. Radial and spatial distribution functions calculated for several ion pair species reveal that the transition from free ions to contact ion pairs involves the loss of between one to two water molecules from the cation depending on the cation size. This is correlated with the experimental hydration numbers calculated for metal sulfate electrolyte solutions at several concentrations using density and ultrasonic velocity measurements. These experiments reveal a decrease in hydration number with an increase in concentration, which can be attributed to the formation of ion pairs. A more complex metal system is the industrially important platinum group metal (PGM) chloro-anion one. Their industrial importance relates to the search for a Green Chemistry Process for the separation of PGM chloro complexes that have been extracted from the mined ore into an acidic aqueous media. This requires a PGM separation process in water. Here an understanding of the hydration structure about the iii PGM chloro-anion complexes and the role that ammonium counter-ions play in disrupting that solvent structure when ammonium PGM salts are formed, is critical in the process design. To this end a solution force field, inclusive of the majority of PGM chloro-anion complexes (i.e. (Y)2[PtCl4]2-, (Y)2[PdCl4]2-, (Y)2[PtCl6]2-, (Y)2[PdCl6]2-, (Y)2[IrCl6]2-, (Y)2[OsCl6]2-, (Y)2[RuCl6]2-, (Y)3[IrCl6]3-, (Y)3[RhCl6]3- and (Y)3[RuCl6]3- , where Y = NH4 +) arising in acidic aqueous media, parameterised from experimental and quantum mechanically derived properties, was developed. Nanosecond atomistic molecular dynamics simulations were then performed for the PGM chloro-anion complexes. Analysis of the solvation structure using radial and spatial distribution functions revealed two distinct solvent structures corresponding to the square planar and octahedral species. The formation of ion pairs disrupts the solvent structure where the hydration shells about the bivalent hexachlorometallates are more affected compared with the trivalent hexachlorometallates and these first shell waters in turn are more affected than those in the bivalent tetrachlorometallates. Finally to inform the design of a separation process transport properties such as diffusion coefficients, ion hydration numbers and water residence times for the PGM chloro-anion complexes were calculated. It is observed that the diffusion rates of PGM chloro-anion complexes are strongly correlated to their ion hydration numbers as calculated by Voronoi tessellation of the simulation cell, such that a larger hydration shell volume results in a slower PGM chloro-anion diffusion rate.

In this thesis, the investigation of the mechanism of chlorine evolution reaction at (i) both freshly reduced and pre-oxidized Pt electrodes; (ii) RuO$\sb2$-TiO$\sb2$ electrodes (DSA); (iii) other noble metals such as Pd, Ir, Ru and Rh by means of computer controlled anodic polarization, potential-relaxation transients and a.c. impedance measurements, will be presented. As described in Chapter V, the influence of co-deposited OH and O species in the surface oxidation process on the extent of chemisorption of the Cl$\sp-$ intermediate in the Cl$\sb2$ evolution reaction has been carefully examined. Experimental results reveal that the reaction rate at reduced Pt surfaces is much greater than that at pre-oxidized ones. This is because the oxide species have a significant effect in blocking the Cl$\sb2$ evolution kinetics. The detectable surface adsorption pseudocapacitance, which is associated with the "overpotential deposited" Cl$\sp-$ intermediate, at freshly reduced Pt and oxide free Pt surfaces in non-aqueous trifluoroacetic acid (TFA) medium supports this conclusion. In Chapter VI, some exploratory experiments at other noble metal (e.g., Pd, Ir, Ru, and Rh) electrodes in non-aqueous TFA solution have shown very interesting interfacial capacitance information, which must be interpreted probably in terms of more than one adsorbed reaction intermediate being present. In Chapter VII, a possible mechanism of recombination kinetically control has been proposed for the Cl$\sb2$ evolution reaction at RuO$\sb2$-TiO$\sb2$ electrodes, based on the observations of their steady-state behaviour, and electrochemical data from potential relaxation and a.c. impedance measurements. Local supersaturation of Cl$\sb2$ in the microstructure of the oxide film appears to make a contribution to the pseudocapacitance behaviour. Some of the results in this work have been published or in press, as listed below: (1) "Surface electrochemistry of the anodic chlorine evolution reaction at Pt influence of co-deposition of the Cl$\sp-$ intermediate", P. Gu and B. E. Conway, J. Chem. Soc. Farada Trans. 86(6) (1990) 923. (2) "Behaviour of the adsorbed Cl$\sp-$ intermediate in anodic chlorine evolution at thin-film RuO$\sb2$ surfaces", P. Gu and B. E. Conway, J. Appl. Electrochem., in press. (3) "Evaluation of Cl$\sp-$ adsorption in anodic chlorine evolution at Pt by means of a.c. impedance and potential relaxation experiments: role of the state of surface oxidation", P. Gu and B. E. Conway, J. Chem. Soc. Faraday Trans., in press.

Platinum group metals (PGMs) are well established and widely used for catalytic processes. It has been demonstrated that PGMs can be superior catalysts for hydrocarbon conversion reactions compared to the industry standard. However, the findings in academic labs cannot always translate directly to industrial usage. One limitation to using PGMs for large scale processes is sometimes cost. Access to an inexpensive and highly efficient catalyst could be a step towards using recovered hydrocarbons, in the form of natural gas and shale gas, more widely for energy production.

While platinum group metal species have been intensively examined, less is know about reactivity associated with ionic PGMs in oxides. Using ionic species could be a route to achieving more efficient conversion of mixed hydrocarbon feedstocks to fuels and commodity chemicals. The work presented in this dissertation focuses on Pd–substitution in binary and complex oxides along with model compounds containing noble metals, with the aim of preparing an inexpensive and robust C–H bond activation catalyst. With an emphasis on preparation methods and careful characterization, it has been a goal of this work to establish structure–property relationships in oxide catalysts.

Initial work on Pd–substitution in CeO₂ has lead to the development of ultrasonic spray pyrolysis (USP) as a method for preparing substituted oxides having relatively high surface area. Phase pure Pd–substituted perovskites were also prepared using this technique. Methane partial oxidation reactions on Pd–substituted CeO₂ provided some understanding of Pd substitution in oxides. It was determined that ionic Pd when substituted in CeO₂ is readily reduced to fcc-Pd. Investigation of more complex oxides that could stabilize ionic Pd under reducing conditions through inductive effects became the target of subsequent research.

Pd-substituted LnFeO₃ (Ln = Y, La) showed promising results for increased stabilization of Pd ions under methane partial oxidation conditions. Microwave-assisted heating methods were employed to prepare these materials very rapidly. With just several minutes of microwave-assisted heating, Pd–substituted perovskite materials were prepared for characterization and testing. With the help of our collaborators, Pd–substituted LaFeO₃ was applied as a catalyst precursor material for aryl chloride coupling under mild conditions.

The focus was shifted to model compounds, noble metal complex oxides, La₂BaPdO₅ and La₂BaPtO₅, already having unique noble metal sites. The thermal stability of these complex oxides compared to binary oxides was both an attractive property for probing ionic PGM catalysis and a fascinating feature, worthy of further investigation. Using density functional theory, the electronic structures of La₂BaPdO ₅ and La₂BaPtO₅ were compared to those of the binary PdO and PtO oxides. It was determined that a shift in the O 2p band is responsible for the increased stability in complex oxides.

Through this study of Pd ions, we have developed two novel methods for preparation of substituted and stiochiometric oxide materials. A combination of characterization methods, including X-ray diffraction and X-ray photoelectron spectroscopy, are required to understand the structure of these complicated materials. Often times, more advanced characterization, such as neutron diffraction and extended X-ray absorption fine structure measurements, provide the necessary insights to understanding the structures and properties of oxide catalysts. In this dissertation, preparation and characterization are emphasized for ionic PGM and oxide catalysts.

Thesis (MSc)--University of Stellenbosch, 2004
ENGLISH ABSTRACT: A variety of computational techniques are used to calculate structural, thermodynamic and transport properties of two specific Platinum Group Metal (PGM) complex systems. The first system consists of a PGM complex ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- or [RhCl6]3-) with sodium counter-ions in a water solution at 30ºC and at a concentration of 0.106 mol/dm3. The second system under consideration is that of a PGM complex ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- or [RhCl6]3-) with sodium counter-ions in a water solution in the presence of four poly (ethylene oxide) (PEO) chains at 30ºC and at a concentration of 0.013 mol/dm3. A conformational study of the two types of dihedral angles in a PEO chain (-C-O-C-Cand -O-C-C-O-) is performed and the extreme flexibility of the polymer is confirmed. Dihedral angle distributions of the two dihedral angles are calculated and explained in terms of the potential energy surface obtained from the conformational study. The solvation geometries of the PGM complexes are confirmed and the results are contrasted with those in the system where the polymer (PEO) is present. It is concluded that the effect of the polymer on the structure and degree of solvation is negligible. The free energy of solvation values of the PGM complexes are calculated to provide insight into their structural characteristics such as solvation shell volume and geometry. The structural and thermodynamic properties of the PGM complexes in solution are also used to explain the trends observed in the calculated diffusion coefficients. Comments are made on the accuracy of the calculated diffusion coefficients as well as the legitimacy of the mechanistic speculations which results from them. Suggestions regarding possible future improvements to the computational methods are made.
AFRIKAANSE OPSOMMING: Verskeie berekenings tegnieke is aangewend om die strukturele, termodinamiese en verplasings eienskappe van twee spesifieke Platinumgroep Metaal (PGM)-kompleks sisteme te bereken. Die eerste sisteem bestaan uit die PGM-kompleks ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- of [RhCl6]3-) met natrium teenione in water by 30ºC en met ‘n konsentrasie van 0.106 mol/dm3. Die tweede sisteem bestaan uit die PGM-kompleks ([PdCl4]2-; [PtCl4]2-; [PtCl6]2- of [RhCl6]3-) met natrium teen-ione in water in die teenwoordigheid van vier poli-etileenoksied (PEO) kettings by 30ºC en met ‘n konsentrasie van 0.013 mol/dm3. ‘n Studie is gemaak van die konformasies van die twee soorte dihedrale-hoeke in ‘n PEOketting (-C-O-C-C- en -O-C-C-O-) en die insense buigbaarheid van die polimeer is hiermee bevestig. Die dihedrale-hoek-verspreidings van die twee tipes dihedrale hoeke is bereken en word verduidelik in terme van die potensiёle energie kromvlakke soos bereken tydens die konformasie analiese. Die geometrie van die solvasie van die PGM-komplekse is bereken en vergelyk met die sisteme waar die polimeer (PEO) teenwoordig is. Hieruit word afgelei dat die effek van die polimeer op die struktuur en graad van solvasie van die komplekse minimal is. Die vrye energie van solvasie van die PGMkomplekse is bereken met die doel om insig in te win oor die stukturele eienskappe soos byvoorbeeld die volume van die solvasie sfeer en die geometrie daarvan. Die strukturele en termodinamiese eienskappe van die PGM-komplekse in oplossing word ook gebruik om die neigings in die berekende diffusie koёffisiente te verduidelik. Opmerkings word gemaak aangaande die akkuraatheid van die berekende diffusie koeffisiente asook die geldigheid van die meganistiese spekulasies wat daaruit gemaak word. Voorstelle word ook gemaak rakende toekomsige verbeterings aan die reken tegnieke.

Rare earth-platinum group mixed metal ozide (RE-PG-O) systems comprise approximately 100 systems. The similarity of ionic radii and electronegativitis within constitutent cation groups (for comparable RE or PG oxidation states) is useful for examining trends in RE-PG-O phase development, and explaining structural stability in terms of tolerance factors. The refractory and electropositive influence of REs in the mixed metal oxide matrix enables less common oxidation states of PGs to be accessed via a novel synthesis technique. RE-PG-O systems are therefore selectively studied under 'neutral', 'reducing' and 'oxidising' conditions. X-ray diffraction methods are used for phase identification and the determination of stability relationships. PGII, PGIII, PGIV and PGV species are encountered in structures such as perovskite, pyrochlore, A3BO7 and Nd2CuO4 types. Re-PG-O systems can be divided into two main groups. The first comprises PG&61 Ru, Ir, Rh and includes structure types which can be described in terms of order-disorder transformations within a fluorite template. Phases in these systems are redox sensitive in both their synthesis and their defect chemistry, a feature which is reflected in their electrical properties; this is often a characteristic of fluorite-derived structures. The second group of RE-PG-O systems is characterised by formation of structures which permit square-planar coordination of PdII and PtII. The influence of REII, REIII and REIV species is considered in RE-PG-O phase development; REIII species predominate. The role of the RE is more subtle in determining the stable structure type since phase development and physical properties can be considered in terms of gradational change across the RE series. This behaviour can be used to detct the occasional presence of any REIV and to 'fine-tune' the physical properties of a given structure type. Generally, the half-filled 4f shell of Gd represents a transition point for polymorphism and RE-PG-O phase stability in the REIII series; the stabilisation of RE-PG-O phases is more difficult beyond Gd. Two novel systems are encountered, La-Ru-O and La-Ir-O. These sytems contain structures with mixed integral PG oxidation states, non-integral delocalised PG oxidation states, and/or metal-metal bonding. La is an unusual RE in that it lacks 4f electrons, in contrast to other REs, but since RE behaviour is dictated largely by 5d and 6s electrons, these novel systems should have features in common with their sister systems. Possible structural relationships are discussed in an attempt to rationalise the behaviour of the La-Ru-O system in particular. This thesis represents the first comprehensive overview of RE-PG-O systems, identifying areas of interest which merit further study.

Includes bibliographical references.
The success of cisplatin and its analogues for the treatment of different cancers has had a profound effect on establishing the application of metal complexes in medicine. Lately, increasing drug resistance and the emergence of unwanted side effects to currently available therapies have bred a need for novel pharmacological agents. Thus, the design and study of organometallic complexes as potential chemotherapeutics may potentially identify new drug candidates. Apart from platinum based compounds, platinum-like metals such as ruthenium(II), rhodium(III) and iridium(III), have been identified as biologically relevant metals. The purpose of this study is to synthesize three classes of polynuclear complexes containing metals from the Platinum Group Metal (PGM) series and evaluate each class for pharmacological activity in vitro. Each complex class is based on a different ligand type. New mono- and polynuclear organometallic Platinum Group Metal (PGM) complexes based on three ligand classes have been synthesised and characterised using several analytical and spectroscopic techniques including 1H, 13C and 31P NMR, infrared and UV-vis spectroscopy. The first complex series is based on the thiourea containing ligand, 3,4-dichloroacetophenonethiosemicarbazone, which has demonstrated in vitro pharmacological activity. This ligand was reacted with K2[PtCl4] to afford a tetranuclear cycloplatinated thiosemicarbazone complex (2.2). Reaction of 2.2 with different mono- and diphosphanes yielded two mono- and three dinuclear Pt(II) thiosemicarbazone ligands (2.3-2.7). In all of the complexes (2.2-2.7), the thiosemicarbazone ligands act as a dinegative tridentate [C,N,S] donor to each metal centre. Single crystal X-ray analyses of three of the complexes in this series, including the tetraplatinum derivative, confirmed the structural integrity of these complexes. Reactivity studies of the mononuclear platinum(II) complexes revealed that one complex is able to undergo oxidative addition reactions with different aryl iodide substrates. In vitro pharmacological studies of a selection of these complexes as antiparasitic agents have been carried out against the P. falciparum strains, D10 (cisplatin sensitive) and Dd2 (cisplatin resistant)) and Trichomonas vaginalis T1. Their cytotoxic effects on the A2780 (cisplatin sensitive) and A2780cisR (cisplatin resistant) human ovarian carcinoma cell line has also been determined. All of the complexes demonstrated moderate cytotoxic effects as antiparasitics and antitumor agents. No correlation between the number of platinumthiosemicarbazone moieties and pharmacological activity could be discerned. Instead, the type of ancillary ligand used to prepare each complex may influence the lipophilic nature of each complex thus explaining the trend observed.

Abstract Platinum group elements (PGEs) have a high commercial value and variety of applications in different fields of industry. One of the well-known applications is the use of palladium, platinum and rhodium in the catalytic converters of automobiles to reduce the amount of harmful gases emitted to the environment. Advanced analytical methods are needed to deal with issues related to development of new catalyst materials, recycling of PGEs from spent materials and for monitoring PGE emissions to the environment. In the first part of this study the emphasis was on the catalyst materials. Especially, reliable determination of ruthenium content in catalyst materials required further studies. Consequently, acid digestions in closed vessels using a microwave oven or high pressure asher were compared with a previously reported fusion method. Furthermore, the recovery of PGEs from spent materials is important due to many factors, for example, the high value of these metals, environmental aspects related to their production and possible availability issues in the future. Thus, utilization of microwave-assisted leaching and cloud point extraction (CPE) for the recovery of palladium, platinum, rhodium and ruthenium from catalyst materials was investigated. The second part of this study concentrated on the PGEs in environmental samples and the analytical challenges related to PGE determinations with inductively coupled plasma mass spectrometry (ICP-MS). Due to the use of PGEs in catalytic converters of automobiles, they are emitted to the roadside environment. The use of Pleurozium schreberi, a terrestrial moss, for active biomonitoring of these emissions was evaluated. Advanced analytical methods were needed to perform interference-free determinations of palladium, platinum and rhodium in these samples. Two alternative approaches for interference elimination were studied. Firstly, the interfering elements were removed using CPE as a chemical separation method. Secondly, interferences were eliminated using ammonia as a reaction gas with the novel ICP-MS/MS (inductively coupled plasma tandem mass spectrometry) technique
Tiivistelmä Platinaryhmän alkuaineita hyödynnetään monissa teknisissä sovelluksissa. Yksi tunnetuimmista on autoliikenteen haitallisten päästöjen vähentäminen käyttäen palladiumia, platinaa ja rodiumia autojen pakokaasukatalysaattoreissa. Luotettavia analyysimenetelmiä tarvitaan esimerkiksi kehitettäessä uusia katalyyttimateriaaleja, kierrätettäessä platinaryhmän alkuaineita käytetyistä materiaaleista tai seurattaessa platinaryhmän alkuaineiden määrää ympäristössä. Tämän tutkimuksen ensimmäinen osa liittyi katalyyttien ruteniumpitoisuuksien määrittämiseen ja platinaryhmän alkuaineiden kierrätykseen katalyyttimateriaaleista. Erityisesti näytteenhajotusvaihe aiheuttaa usein ongelmia ruteniummäärityksissä. Tämän vuoksi tutkimuksessa verrattiin keskenään mikroaaltotekniikalla tai korkeapainetuhkistimella suoritettuja happohajotuksia ja aiemmin raportoidulla sulatemenetelmällä suoritettuja hajotuksia. Mikroaaltoavusteista liuotusta sovellettiin yhdessä samepisteuuton kanssa tutkittaessa katalyyttimateriaalien palladiumin, platinan, rodiumin ja ruteniumin kierrätysmahdollisuuksia. Aihe on ajankohtainen, kun huomioidaan platinaryhmän alkuaineiden korkea hinta, niiden tuotantoon liittyvät ympäristöasiat sekä saatavuuteen liittyvät epävarmuustekijät. Tutkimuksen toisessa osassa keskityttiin ympäristönäytteisiin ja erityisesti niiden ICP-MS -analytiikan (induktiiviplasmamassaspektrometria) haasteisiin. Autojen katalysaattoreista lähtöisin olevia platinaryhmän alkuaineita päätyy ympäristöön lähinnä teiden varsille. Näitä päästöjä arvioitiin aktiivista biomonitorointia käyttäen. Spektraaliset häiriöt vaikeuttivat kerättyjen sammalnäytteiden (Pleurozium schreberi) palladium-, platina- ja rodiumpitoisuuksien määrityksiä. Tämän vuoksi mittauksissa esiintyvien häiriöiden poistossa hyödynnettiin kahta eri lähestymistapaa. Näistä ensimmäisessä häiritsevät alkuaineet poistettiin kemiallisen erotusmenetelmän, samepisteuuton, avulla. Toisessa tavassa häiriöt poistettiin uudella ICP-MS/MS -tekniikalla (induktiiviplasmatandemmassaspektrometria) käyttäen ammoniakkia reaktiokaasuna

Includes abstract.
Includes bibliographical references.
The PGMs, which are comprised of Ru, Pt, Rh, Ir, Os and Pd, are highly regarded as technologically important precious metals. They have a wide range of applications and are used predominantly as catalysts. These metals are found collectively in nature and hence have similar chemical properties. This makes their separation from contaminants and each other a cumbersome process that requires the most technologically sophisticated refinery processes in metallurgical extraction. An efficient method in which these metal complexes are separated is based on gel chromatography. This uses a concentrated aqueous acidic medium, predominantly hydrochloric acid, and their separation is achieved through differentiation of their different elution orders. However, the similarity in their chemistry makes their separation via current experimental methods difficult.

The importance of porous materials has risen substantially in the last few decades due to their ability to reduce the size and cost of bioanalytical devices and fuel cells. First, this work aims to describe the fabrication of nanoporous gold (NPG) electrodes that are resistant to electrode passivation due to fibrinogen biofouling in redox solutions. The effect on potentiometric and voltammetric experiments was seen as a deviation from ideal behavior on planar gold electrodes, whereas NPG electrodes were consistently behaving in a Nernstian fashion at low concentrations of ferri-ferrocyanide (£100 mM). An improvement in electrode behavior on NPG electrodes versus planar gold was seen in solutions containing ascorbic acid as well as blood plasma. Second, cost effective NPG electrodes were fabricated using a glass substrate to test the response in the presence of a variety of redox molecules. The optical transparency of these electrodes allowed for microdroplet measurements to be made using an inverted microscope in several redox solutions for validation and subsequent biological applicability. Nernstian behavior was demonstrated for all one- and two-electron transfer systems in both poised and unpoised solutions. All experiments were conducted using volumes between 280 and 1400 pL producing rapid results in less than one minute. Third, in order to decrease the requirement for complex instrumentation, microdroplet fabrication technique was used to create mini-nanoporous gold (mNPG) electrodes on glass capillary tubes. The cylindrical shape of the electrodes allowed for testing in sample volumes of 100 mL. The response to ferri-ferrocyanide, ascorbic acid, cysteine, and uric acid was then investigated with Nernstian behavior shown. However, the mNPG electrodes were insensitive to glucose and hydrogen peroxide. In order to increase the sensitivity of the electrodes, a minimal amount of platinum was electrodeposited onto the NPG surface using a low concentration of platinum salt (0.75 mM) for a short deposition time (2 seconds) producing a Nernstian response to both glucose and hydrogen peroxide. Lastly, to test the viability of crossover applications, the platinum incorporated NPG electrode was employed as a fuel cell anode material, testing their oxidation capability with methanol, ethanol, and formic acid.

The accuracy and precision of catalytic converter analysis using conventional analytical methodology such as fire assay, x-ray fluorescence, atomic absorption and ICP-AES are typically in the range of ±7-10% RSD. Due to the high cost of noble metals, methods of analysis with increased accuracy and precision are desired to evaluate the loading of noble metals onto converter bricks. The investigations described in this work have resulted in a better understanding of many of the inherent problems and have contributed new approaches for sample dissolution and analysis using array detector based Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). These methods are shown to be accurate and precise for the analysis of Pt, Pd, and Rh in catalytic converters. Catalytic converters are difficult to dissolve by conventional acid methodology. While carius, tubes have previously been employed to dissolve small weights of sample, complete dissolution of increased amounts of sample, as needed for high precision ICP-AES analysis, has been hindered by the insufficient oxidation potential of the acids in the carius tube. In this work, the addition of ferric chloride is shown to increase the dissolving power of the carius tube method and specifically targets Pt, Pd and Rh for dissolution. Simultaneous collection of analyte wavelengths and simultaneous background correction, as performed with multichannel array detector ICP-AES instrumentation, have enhanced sensitivity and precision in catalytic converter analysis when compared to single channel instrumentation. The studies described within this dissertation demonstrate that flicker noise has been effectively eliminated through the use of multichannel array based ICP-AES instrumentation. With proper line selection and the use of the high-resolution system, Pt, Pd and Rh in catalytic converters can be analyzed with precision of 1-1.5%. ICP-AES accuracy has been confirmed through isotope dilution ICP-MS employing new methodology to avoid Zr isobaric interferences.

Organic thin films (alkanethiolates chemisorbed on gold) were employed in low-energy (eV) ion-surface collisions to validate the technique as a surface analysis tool and to further investigate processes associated with ion-surface interactions. Low-energy ion surface collisions of small polyatomic and atomic ions with self-assembled monolayers (SAMs) ascertain the chemical composition, structure, and quality of SAMs utilizing four processes: energy transfer (fragmentation of projectile ions: surface-induced dissociation (SID)), electron transfer (neutralization of the projectile ions), atom/group transfer (reaction between the projectile ion and atom/groups from SAMs), and chemical sputtering. Low-energy ion-surface collisions were used to investigate newly synthesized fluorinated compounds where the degree of fluorination of the thiolate tail group increases. Data indicate that substitution of CH₃ with CF₃ as the terminal group has a substantial influence on energy transfer, electron transfer, and atom/group transfer. Slight penetration into a depth of SAM films is illustrated by the formation of certain ion-surface reaction products (a result not observed for previously characterized Langmuir-Blodgett (L-B) films). A novel neutralization mechanism for reaction between methyl cation and hydrocarbon and fluorocarbon SAMs was established. Ion neutralization (besides direct electron transfer) results from a hydride ion transfer, methyl anion transfer, or fluoride transfer between hydrocarbon and fluorocarbon SAMs and incoming methyl cations. Experimental ion-surface and ion-molecule data support the ion neutralization mechanism originally proposed by ab initio and thermochemical calculations. Ion-surface processes were also used to characterize three mixed SAM systems (system 1: hydroxyl/hydrocarbon mixed SAMs and systems 2 and 3: fluorocarbon/hydrocarbon mixed SAMs). The mixed SAMs were prepared from binary thiol solutions and uniform solutions of asymmetrical disulfides. These ion-surface data can be useful for qualitative (identification of the sample's chemical composition) and quantitative analysis (calculation of the surface concentration of a chemical species for a mixed SAM). An in-line Sector-Time-of-Flight (TOF) tandem mass spectrometer with low-energy ion-surface collisions was characterized. Research involved testing the versatility of the instrument in terms of effective ion activation (peptide fragmentation) and surface analysis of organic thin films. This prototype will aid further implementation of SID into commercial TOF instruments for efficient ion activation and surface analysis capabilities.

Includes bibliographical references.
In this project a series of multinuclear complexes were successfully prepared and characterised using an array of analytical techniques. The use of nitrogen-donor ligands, in particular pyridine and ferrocenyl derivatives thereof was examined. Two main approaches were taken in the preparation of the ferrocenylpyridines: i. The ferrocenylpyridines were systematically studied by varying the position of substituents along the pyridyl ring in the 4-,3-and 2-positions. ii. The effect of placing spacer groups between the ferrocenyl group and the pendant pyridine was examined. iii. The ligands were prepared with a system of conjugated π bonds, allowing for an electronic pathway within the ligand.

Nitrogen-doped carbon materials have garnered much interest due to their abilities to behave as electrocatalysts for reactions important in energy production (oxygen reduction) and biosensing (hydrogen peroxide reduction). Here, we demonstrate fabrication methods and determine electrocatalytic properties of nitrogen-doped screen-printed carbon (N-SPCE) electrodes. Nitrogen doping of graphite was achieved through a simple soft-nitriding technique which was then used in lab-formulated screen-printing inks to prepare N-SPCEs. N-SPCEs displayed good electrocatalytic activity, reproducibility and long term stability towards the electrochemical reduction of hydrogen peroxide. N-SPCEs exhibited a wide linear range (20 µM to 5.3 mM), reasonable limit of detection of 2.5 µM, with an applied potential of -0.4 V (vs. Ag/AgCl). We also demonstrate that nitrided-graphite can similarly be used as a platform for the deposition of electrocatalytic platinum nanoparticles, resulting in Pt-N-SPCEs with a lower limit of detection (0.4 µM) and better sensitivity (0.52 µA cm-2 µM-1) towards H2O2 reduction.

Platinum compounds are widely used drugs in cancer treatments. Although DNA is the biological target, reaction of platinum compounds with proteins is also potentially significant. Our objective is to study the effects of leaving ligands on the relative reactivity between 5'-GMP (guanosine 5' phosphate), a key DNA target, and N-Acetyl - L-Methionine (N-AcMet), a key protein target. We have used NMR spectroscopy to monitor reactions with N-AcMet and 5'-GMP added to a platinum complex to see which products are formed preferentially. Previous research showed that both a non-bulky complex such as [Pt(en)(D2O)2]2+ [en=ethylenediamine], and a bulky complex such as [Pt(Me4en)(D2O)2]2+ [Me4en= N, N, N', N'-tetramethylethylenediamine] react more quickly with 5'-GMP than with N-AcMet. To improve the activity of platinum compounds in our current research, oxalates as leaving ligands are used. The results suggest that [Pt(en)(Ox)] [Ox= oxalate] reacts faster with N-AcMet than with 5'-GMP. Also, [Pt(Me4en)(Ox)] reacts slowly with 5'-GMP without N-AcMet and the reaction favors N-AcMet when both ligands are added simultaneously. Interestingly, the formation of the sulfur-oxygen chelate is slow enough to be observable in the oxalate reaction; but the mono product is not independently observed in the dinitrate complex.

Proteins have evolved over millions of years to serve a plethora of highly specialized functions in biological systems. Given the enormous diversity in structure and function, it is truly surprising that only 20 different amino acids are utilized as the building blocks of proteins. Furthermore, only a small set of metal cations that are biologically available are used as structural or catalytically active cofactors in proteins, whereas rare metal cations such as platinum, ruthenium or rhodium remain absent. In the 20th century myriad catalysts, based on non-biological transition metals, emerged that can facilitate numerous organic transformations. The goal of the thesis was to introduce new functions into proteins by attaching platinum metals and fluorescent metal sensors. Thus, semi-synthetic proteins for catalytic and analytical applications were generated. The replacement of organic solvents by environmentally benign solvents such as water is an imperative step towards achieving "green chemistry". The combination of small molecule catalysts with proteins may introduce new functions and take advantage of the benefits of "both worlds" while avoiding their potential drawbacks. Therefore semi-synthetic catalysts were developed for enantioselective organic reactions in aqueous medium. A suitable reaction, reaction conditions and catalytic system for later utilization in a semi-synthetic protein were designed, developed and characterized. Ruthenium porphyrins catalyzed cyclopropanation reactions with fair yields and high stereoselectivity in aqueous medium. The successful reaction in water was a crucial requirement for a catalytically active semi-synthetic protein. Mechanistic studies did not elucidate the actual catalytic species for the formation of the cyclopropanation product and the side-product diethyl maleate; however, new insights were gained from the analysis of potential reaction pathways. Moreover, studies of the influence of axial ligands, resembling likely residues coordinating to the ruthenium metal center in the active site of a semi-synthetic protein, on the carbene formation of ruthenium porphyrins illustrated that coordination of axial ligands may inhibit the catalytic activity. The generation of ruthenium porphyrin based semi-synthetic proteins and their subsequent catalysis of cyclopropanation reactions was carried out. Myoglobin and myoglobin mutants were successfully reconstituted with a heme-like ruthenium carbonyl porphyrin; however, none of the formed semi-synthetic proteins catalyzed the enantioselective cyclopropanation of styrene. Efforts to determine the reconstitution efficiency of the generated semi-synthetic were hampered by problems to purify the generated semi-synthetic proteins that are probably due to non-specific binding of the ruthenium porphyrin to the protein surface. The exploration of labile metal pools of the biologically relevant transition metals copper, iron and zinc in cells was the goal of developing semi-synthetic proteins for analytical applications. Combining fluorescent proteins with colored or fluorescent metal chelators by forming semi-synthetic proteins allows taking advantage of their beneficial properties while avoiding their downsides. This design offers an attractive platform for in vivo metal sensing. Plasmids encoding fluorescent proteins, targeting sequences and AGT or intein fusion domains (necessary for labeling) for eukaryotic and prokaryotic expression were generated. The targeting of intracellular compartments (mitochondria, nucleus and TGN) was successful (confirmed by light microscopy experiments with transfected mammalian cells). In vitro labeling experiments of expressed and purified fusion proteins with rhodamine derivatives succeeded with AGT based fusion proteins; however, labeling of fusion proteins by trans-splicing with split-inteins failed. A new Zinc(II)-chelator was attached to an AGT based protein and the resulting semi-synthetic protein exhibited strong changes of fluorescence in the presence of zinc(II). This represents an important step towards the goal of in vivo cell imaging of labile zinc(II) pools. Despite extensive efforts, all attempts failed to generate a chelator that forms Cu(I)-complexes with the 1:1 stochiometry (ligand:metal) that is necessary for metal sensing with semi-synthetic proteins.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: In Base Metal Refineries (BMRs), the copper sulphate leach solution produced during the final pressure leaching stage contains impurities such as selenium and tellurium, as well as other precious metals (OPMs, namely Rh, Ru, and Ir). Se and Te are removed by precipitation with sulphur dioxide prior to electrowinning of Cu. While a small percentage of the dissolved OPMs precipitate with the Se and Te, the largest portion remains in solution and is recycled to the first stage leach. If a larger portion of the OPMs in solution can be recovered in the Se/Te precipitation stage, OPM losses and the OPM inventory of the plant can be reduced. The aim of this project was to determine operating conditions that would allow maximum OPM recovery with minimal Cu and Ni co-precipitation in the Se/Te removal section of a BMR. The effects that the operating temperature, pressure, stirring rate, reagent type, and reagent quantity have on the metal precipitation behavior and precipitate characteristics were determined experimentally. Thio-urea and sulphurous acid were evaluated as precipitation reagents for temperatures of 80°C and 160°C, stirring rates of 250 rpm and 500 rpm, and pressures equal to ambient pressure and 7 bar. 200 % and 320 % excess thio-urea and 720 % and 960 % excess sulphur dioxide were used. The precipitation of OPMs with sulphur dioxide was generally poor; the maximum percentage Rh, Ru, and Ir precipitated were 35 %, 18 %, and 20 %, respectively. It was, however, found that the OPM precipitation increased as the reagent amount was increased. Increasing the temperature further increased Rh and Ir precipitation but affected the Ru precipitation negatively. Thio-urea precipitated virtually all of the Rh contained in the solution irrespective of the values of the process variables studied. As was the case with sulphur dioxide, increasing the amount of thio-urea added resulted in increased Ru and Ir precipitation, while higher temperatures favored Ir precipitation but not Ru precipitation. The maximum percentage Ru and Ir precipitation achieved with thio-urea were 87 % and 60 %, respectively. Complete Se precipitation was observed at all process conditions, while Te precipitation increased as the operating temperature and the reagent quantity were increased. Maximum Te precipitation of 98 % and 90 % were achieved when using 320 % excess thio-urea and 960 % sulphurous acid quantities, respectively, at 160°C and a stirring rate of 250 rpm. Increasing the reagent quantity and temperature did, however, also result in increased copper and nickel precipitation. The statistical analysis of the results allowed regression models to be fitted to predict the percentage metal precipitation as a function of the investigated process variables. These models were used to define an objective function to determine the optimal operating conditions. A temperature of 80oC, a pressure of 7 bar, and 200 % excess thio-urea were proposed as the optimum operating conditions that would yield 98 % Rh, 75 % Ru, and 48 % Ir precipitation with less than 5 % Cu and Ni co-precipitation. Experimental validation tests confirmed the model predicted values and proved repeatability of the experimental data.
AFRIKAANSE OPSOMMING: Die kopersulfaat logingsoplossing wat tydens die finale drukloging stadium in Basis Metaal Raffinaderye (BMRe) produseer word, bevat onsuiwerhede soos selenium en tellurium sowel as ander edelmetale (AEMe, naamlik Rh, Ru, en Ir). Se en Te word voor Cu elektrowinning verwyder deur middel van presipitasie met swaweldioksied. Alhoewel ʼn klein persentasie van die opgeloste AEMe saam met die Se en Te presipiteer, bly die grootste gedeelte in oplossing en word gevolglik na die eerste loging stadium hersirkuleer. AEM verliese en die AEM inventaris van die aanleg kan verminder word indien ʼn groter gedeelte van die AEMe in die Se/Te presipitasie stadium herwin kan word. Die doel van hierdie projek was om bedryfstoestande te bepaal om maksimum AEM herwinning met minimale Cu en Ni kopresipitasie in die Se/Te verwyderingseksie van ʼn BMR te behaal. Die effekte wat bedryfstoestande soos temperatuur, druk, roerder tempo, tipe reagens, en hoeveelheid reagens op die metaal presipitasiegedrag en presipitaat eienskappe het, is eksperimenteel bepaal. Tio-ureum en swaweligsuur is evalueer as presipitasie reagense vir temperature van 80°C en 160°C, roerder tempo’s van 250 rpm en 500 rpm, en drukke gelyk aan omgewingsdruk en 7 bar. 200 % en 320 % oormaat tio-ureum en 720 % en 960 % oormaat swaweldioksied is gebruik. Die presipitasie van AEMe met swaweldioksied was swak in die algemeen; die maksimum persentasie Rh, Ru, en Ir presipitasie wat behaal is, is 35 %, 18 %, en 20 %, onderskeidelik. Daar is egter gevind dat die AEM presipitasie toeneem indien die hoeveelheid reagens toeneem. ʼn Toename in die temperatuur het verder tot ʼn toename in Rh en Ir presipitasie gelei, maar dit het Ru presipitasie negatief affekteer. Tio-ureum het basies al die Rh in oplossing laat presipiteer, ongeag die waardes van die ander prosesveranderlikes wat ondersoek is. Soos wat die geval vir swaweldioksied was, het ʼn toename in die hoeveelheid tio-ureum ʼn toename in die Ru en Ir presipitasie tot gevolg gehad, terwyl hoër temperature Ir presipitasie bevoordeel en Ru presipitasie benadeel het. Die maksimum persentasie Ru en Ir presipitasie wat met tio-ureum behaal is, is 87 % en 60 %, onderskeidelik. Volledige Se presipitasie is by alle proses toestande waargeneem, terwyl Te presipitasie toegeneem het soos wat die temperatuur en die hoeveelheid reagens toegeneem het. Maksimum Te presipitasie van 98 % en 90 % is behaal toe 320 % oormaat tio-ureum en 960 % oormaat swaweligsuur, onderskeidelik, by 160°C en ʼn roerder tempo van 250 rpm gebruik is. ʼn Toename in die hoeveelheid reagens en die temperatuur het egter ook meer koper en nikkel presipitasie tot gevolg gehad. Die statistiese analise van die resultate het dit moontlik gemaak om regressie modelle te pas om die persentasie metaal presipitasie as ʼn funksie van die ondersoekte veranderlikes te voorspel. Hierdie modelle is gebruik om ʼn doelfunksie te definieer ten einde die optimale bedryfstoestande te bepaal. ʼn Temperatuur van 80°C, ʼn druk van 7 bar, en 200 % oormaat tioureum is voorgestel as die optimale bedryfstoestande wat 98 % Rh, 75 % Ru, en 48 % Ir presipitasie met minder as 5 % Cu en Ni kopresipitasie tot gevolg sal hê. Eksperimentele geldigheidsbepalingtoetse het die waardes wat deur die modelle voorspel is bevestig en die herhaalbaarheid van die eksperimentele data bewys.

The scientific progress about the important chemotherapeutic drug substance cisplatin (CDDP) and its function has often been rendered by data difficult to interpret, and still many questions about its mode of action remains to be clarified by the scientific community. However, studies of CDDP possess a high complexity due to; i) low intracellular concentration, ii) many potential biomolecule targets, iii) poor or unknown stability of the intact drug and its biomolecule adducts and iv) complex and varying sample matrices. Metallomic studies, using advanced analytical techniques may contribute to clarify the interactions between CDDP and intracellular biomolecules. For a successful outcome sample preparation conditions as well as separation and detection techniques must be carefully selected and optimized to achieve accurate results and correct interpretation of data.         This thesis describes some new and improved analytical methodologies for characterizing the Pt metallome in CDDP-exposed malignant cells. The developed methods are based on powerful liquid chromatography (LC) methods hyphenated to sensitive detection by inductively coupled plasma- (ICP) and electrospray ionization mass spectrometry (ESIMS). Consideration has also been taken about sample preparation conditions.         By selecting “chemically inert” sample preparation (cell lysis by osmosis) and separation (using only nonreactive or no additatives) conditions we could avoid the formation of platinum artifact compounds previously described in the literature (Paper I and II). Using oxygen containing organic solvents with high boiling points (dimethylformamide; DMF, 1,4-dioxane, n-propanol and ethanol) as alternatives to acetonitrile in the LC separations, significant improvements were achieved in ICPMS sensitivity and robustness. When evaluated in combination with chromatographic performance and ESIMS detection the overall best performance was achieved with n-propanol (Paper II, III and IV). From the studies in Paper II we could show that free intact CDDP can be found in malignant cells, as supporting evidence for passive or endocytotic uptake of the drug and further estimate a half-life for intracellular CDDP to about 15 minutes. Such data has not been shown before. In Paper V, the above improved LC methods were used to demonstrate differences in the platinum and cupper metallome from sensitive and resistant T289 melanoma cells exposed to CDDP at near clinical levels.         In a wider perspective we have shown the potential of using hydrophilic liquid interaction chromatography (HILIC) hyphenated to ICPMS detection as a general approach for analysis of hydrophilic metallo-compounds (Paper II). Taking advantage of the superior ICPMS performance using n-propanol gradients for reversed phase liquid chromatography (RPLC) possess a true alternative and /or complimentary technique to size exclusion chromatography (SEC) commonly applied within metallomic studies of biomolecules (Paper V). Using n-propanol in HILIC as well as in RPLC enables parallel detection by ICP- and ESIMS using only one set of chromatographic parameters (Paper III and IV), something commonly called for by scientists in the field.

Includes bibliographical references.
The trace analysis of the platinum-group metals in complex, severely interfering matrices, such as industrial effluent, has been the focus of much research in_the past forty years. However, despite the greater availability of much improved instrumentation, such as ICP-OES, NAA and XRF, most analytical techniques currently employed for the determination of the platinum-group metals require selective sample preparation that ensures enrichment of the individual platinum-group metals at the trace and ultra trace level, along with simultaneous matrix removal, prior to determination. N-benzoyl-N', N'-dialkylthioureas act as selective complexing agents for the enrichment of platinum-group metals from strongly interfering matrices. This study describes the development of selective pre-concentration methodology for some of the platinum-group metals in post- processing effiuents (using this class of ligands) followed by their direct determination by ICP- OES, in an effort to recover the residual platinum-group metals present in real waste effiuents that are currently unable to be recovered, representing a substantial loss of income to the South African platinum-group metal producers.

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.

Thesis (MEng) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: In this study, SiC reduction of Rowland and Easterns LG (Low Grade) concentrates was investigated. The purpose of the study was to investigate the feasibility of SiC as reductant with respect to metal fall, PGM grade in the alloy, slag composition, Cr solubility and overall PGM recovery. The integration of such process in the current matte-based collection process was also investigated. Currently, the matted-based collection process is most widely used for PGM recovery, but because PGM containing concentrates are becoming more enriched with UG2 (Upper Group 2) LG concentrates, it is expected to be integrated or replaced with an alloy collection process. This kind of process offers greater flexibility to the different types of ore that could be used. The process is chromium tolerant and environmentally friendly. For this purpose Rowland and Easterns UG2 LG Concentrate samples from Lonmin Western Platinum Limited were analysed with XRD, XRF and ICP-MS and it was found that SiO2 and MgO are the most abundant oxides and Pd is the most abundant element from the PGMs. Sulphide bearing minerals such as chalcopyrite were detected in low concentrations (below 1 %) and Cr2O3 concentrations are between 2 – 4 %. The FeO/SiO2 ratio was lower in Rowland LG concentrate. SiC reduction of Rowland and Easterns concentrate was done at 1600℃. Reductant to concentrate ratios for laboratory scale experiments were ranged from 2.5 to 3.5 kg SiC / 100 kg concentrate. SiC reduction of Rowland concentrate had different reduction times. The duration of reduction experiments ranged from 30 - 180 min. PGM recoveries from SiC reduction of Rowland concentrate were very poor (below 10 %) and Fe recoveries were lower than 50 %. A slag viscosity at the end of the melt of more than 4 poise was responsible for poor phase separation. SEM images revealed metal prills entrained in the slag phase instead of settling and combining to the alloy globule at the bottom of the crucible. However, PGM recoveries from SiC reduction of Easterns concentrate was significantly better. More than 85 % of Ir and Pd and almost 60 % of Pt were recovered in a test with a reductant to concentrate ratio of 3.5 kg SiC / 100 kg Easterns concentrate. Fe recovery was also the highest at 66%. Cr and Si concentrations were below 5 % in total. The slag viscosity at the end of melt was calculated to be less than 4 poise and a SEM image of a slag sample revealed few entrained metal prills. After the above findings on the importance of viscosity, it was decided to increase the FeO content in the initial concentrate charge in order to decrease slag viscosity, increase metal fall (PGM collecting phase) and further increase PGM recovery. Peirce-Smith converter slag was used for this purpose. A test was conducted with the addition of 10 kg converter slag / 100 kg Easterns concentrate. The reductant to concentrate ratio was kept at 3.5 kg SiC / 100 kg Easterns concentrate. The results revealed that Ir and Pd recoveries were more than 95%, while Pt recovery was almost 70%. Fe recovery increased to 76 %. On the basis of the results from the test, an optimum feed ratio between Easterns LG concentrate, Rowland concentrate and Peirce-Smith converter slag was calculated. Thermodynamic phase equilibrium calculations predicted that the concentrate charge should consist of 60 - 80% Easterns concentrate with a slag addition of 30 – 40 kg converter slag / 100 kg LG concentrate. SiC reduction of this optimum LG concentrate charge is expected to recover more than 90% of all PGMs. Cr and Si concentrations in the alloy will be below 1 % in total. The amount of converter slag as an addition will be however limited by final PGM grade in the alloy, furnace slag quantities recycled and slag resistivity required in the alloy furnace. The effectiveness of SiC as reductant was also compared to C reduction. C reduction of an optimum concentrate charge had a marginally higher metal fall at the same reductant to concentrate ratio than SiC reduction of an optimum concentrate charge. However, gas emissions are on average 3 times higher for C reduction of a concentrate charge and C reduction requires at least 300 MJ more to smelt 1 ton of LG concentrate than SiC reduction. This is mostly due to C reacting endothermically with FeO to produce Fe(l) and CO(g) in contrast to SiC reacting exothermically with FeO to produce Fe(l), SiO2(l) and CO(g). Integrating SiC reduction of LG concentrates into the existing smelting route at Lonmin was also proposed through a process flow diagram. From an economic point of view, it was found that SiC reduction of 1 ton of LG concentrate charge with a converter slag addition requires almost 700 MJ more than the smelting of a UG2 blended concentrate to produce a matte phase. However it must be taken into account that the sulphide rich layers in the Bushveld complex are being depleted rapidly and alternative processes such as SiC reduction and alloy collection process will be utilized faster than expected. Moreover, gas emissions from reductive smelting is considerably lower, hence it is a more environmentally friendly process. Finally, from the findings of this study, it could be said that base metals and PGMs could be recovered in an iron alloy from SiC reduction of LG concentrate with converter slag additions. Therefore integrating such a process into the matte-based collection process could be considered as a future alternative to smelting UG2 LG concentrates.
AFRIKAANSE OPSOMMING: In hierdie studie, word SiC reduksie met Rowland en Oostelikes LG (Lae Graad) konsentrate ondersoek. Die doel van die studie was om die doeltreffendheid van SiC as reduktant te ondersoek met betrekking tot metaalval, PGM graad in die allooi, slaksamestelling (spesifiek word daar gekyk na Cr oplosbaarheid) en algehele PGM herwinning. Die integrasie van die proses in die huidige mat-gebaseerde versamelingproses word ook ondersoek. Tans word die mat-gebaseerde versamelingproses die algemeenste gebruik om PGM'e te kollekteer, maar omdat PGM konsentrate al hoe meer verryk word met UG2 (Upper Group 2) LG konsentrate, word daar verwag dat dit geïntegreer of vervang gaan word met 'n allooi-versamelingproses. Hierdie tipe proses bied groter buigsaamheid om die verskillende reekse van erts wat gebruik kan word. Die proses kan ook chroom hanteer en is omgewingsvriendelik. Vir hierdie doel was Rowland en Oostelikes UG2 LG konsentraatmonsters van Lonmin Western Platinum Limited ontleed met XRD, XRF en ICP -MS en met die ontleding was daar gevind dat SiO2 en MgO die volopste oksides was en dat Pd die volopste elemente van die PGMe was. Sulfiedminerale soos chalkopiriet is in lae konsentrasies opgespoor (minder as 1%) en Cr2O3 konsentrasies is tussen 2-4 %. Die FeO/SiO2 verhouding was laer in Rowland konsentraat. SiC reduksie van Rowland en Oostelikes konsentrate is teen 1600 ℃ uitgevoer. Die reduktant tot konsentraat verhouding vir laboratoriumskaal eksperimente het gewissel van 2.5 – 3.5 kg SiC / 100 kg konsentraat. SiC reduksie van Rowland LG konsentraat het verskillende reduksie tye gehad. Die duur van die reduksie eksperimente het gewissel van 30-180 min. PGM herwinning van SiC reduksie met Rowland konsentreer was baie laag (onder 10 %) en Fe herwinning was minder as 50%. 'n Slakviskositeit aan die einde van die smelt was hoër as 4 poise en was verantwoordelik vir die swak skeiding van fases. SEM beelde het gewys dat fyn metaalstukkies opgehou was in die slakfase in plaas daarvan dat dit vestig en kombineer met die allooibolletjie aan die onderkant van die smeltkroes. In teenstelling was die PGM herwinning van SiC reduksie met Oostelikes konsentraat aansienlik beter. Meer as 85 % van Ir en Pd was herwin en byna 60% van Pt was herwin tydens 'n toets met 'n reduktant tot konsentraat verhouding van 3.5 kg SiC / 100 kg Oostelikes konsentraat. Fe herwinning was 66% en was ook die hoogste van al die eksperimente. Cr en Si konsentrasies was minder as 5 % in totaal. Die slakviskositeit aan die einde van smelt was bereken en is minder as 4 posie. 'n SEM beeld van 'n slakmonster het baie min vasgevangde metaalstukkies getoon. Na afloop van die bogenoemde bevindinge oor die belangrikheid van viskositeit, was daar besluit om die FeO inhoud van die aanvanklike konsentraat te verhoog. Dit was gedoen om die slakviskositeit te verminder, die metaalval (PGM kollektering fase) te verhoog en sodoende die PGM herwinning verder te verbeter. Vir die doel was Peirce -Smith omskakelaarslak gebruik. ʼn Toets was uitgevoer met die toevoeging van 10 kg omskakelaarslak / 100 kg Oostelikes konsentraat. Die reduktant tot konsentraat verhouding was behou by 3.5 kg SiC / 100 kg Oostelikes konsentraat. Die resultate het getoon dat meer as 95 % van Ir en Pd herwin was, terwyl byna 70 % Pt herwin was. Die Fe herwinning het toegeneem tot 76%. Op grond van die resultate van die toets, is 'n optimale verhouding tussen Oostelikes konsentraat, Rowland konsentraat en Peirce -Smith omskakelaarslak bereken. Termodinamiese modellering voorspel dat die begin LG konsentraat voer uit 60 – 80 % Oostelikes konsentraat moet bestaan, met 'n slak toevoeging van 30 – 40 kg omskakelaarslak / 100 kg LG konsentraat. Daar word verwag dat meer as 90 % van PGM'e herwin sal word vanaf SiC reduksie met ʼn optimum LG konsentraat voer. Cr en Si konsentrasies in die allooi sal minder as 1% in totaal wees. Die hoeveelheid slak wat bygevoeg kan word sal egter beperk word deur die finale PGM graad in die allooi, oond-slak hoeveelhede wat herwin kan word en slakweerstand wat benodig word in die allooi-oond. Die effektiwiteit van SiC as reduktant is ook vergelyk met C reduksie. C reduksie van ʼn optimale konsentraatvoer het 'n effens hoër metaalval wanneer dieselde reduktant tot konsentraat verhouding behou was vir SiC reduksie van 'n optimale konsentraatvoer. Gas hoeveelhede van C reduksie is gemiddeld 3 keer meer en vereis te minste 300 MJ meer om 1 ton LG konsentraat te smelt. Dit is hoofsaaklik te wydte aan C wat endotermies reageer met FeO om Fe (l) en CO (g) te produseer, in teenstelling met SiC wat eksotermies reageer met FeO om Fe (l), SiO2(l) en CO (g) te produseer. Integrasie van SiC reduksie met LG konsentrate in die bestaande smeltroete by Lonmin Western Platinum Limited is ook voorgestel deur 'n proses vloeidiagram. Uit 'n ekonomiese oogpunt, is daar gevind dat SiC reduksie van 1 ton LG konsentraatvoer met 'n omskakelaarslak byvoeging ongeveer 700 MJ meer benodig as om 1 ton UG2 gemengde konsentraat te smelt en 'n mat-fase te produseer. Dit moet wel in ag geneem word dat die sulfied ryk lae in die Bosveld-kompleks vinnig uitgeput word en dat hierdie alternatiewe prosesse soos SiC reduksie en ʼn allooiversameling proses vinniger as verwagtend benut sal word. Verder, gas hoeveelhede van SiC reduksie is laer en daarom is dit 'n meer omgewingsvriendelik proses. Ten slotte, vanaf die bevindinge van hierdie studie, kan dit gesê word dat basismetale en PGM'e in 'n ysterallooi herwin kan word deur middel van SiC reduksie met LG konsentrate en die toevoeging van omskakelaarslak. Daarom kan die integrasie van so 'n proses in die huidige mat-gebaseerde versameling proses beskou word as 'n alternatief vir die toekoms om UG2 LG konsentrate te smelt.

A baseline survey of contemporary fluvial sediments in the Kentish Stour, east Kent, England, has been undertaken to document the sources and distribution patterns of anthropogenic PGE in an attempt to constrain some of the physical and chemical parameters that may influence the distribution of these elements. Nine sedimentary rocks, four motorway-runoff sediments and twenty-one river sediments were analysed for PGE by NiS fire assay pre-concentration and ICP-MS. The highest element abundances occur in a sample of ashed sewage sludge (total PGE content of 392 ng/g), whilst the lowest values were recorded in the soils and sedimentary rocks. The total PGE content of the river sediments ranged from 0.4 to 14.2 ng/g in 1999 and from 0.6 to 167 ng/g in 2001, and exhibited significant variation along the river. This variation corresponds strongly with land use changes (urban versus rural) and with points of discharge from sewage treatment works. The PGE and trace element concentrations of the river sediments, sedimentary rocks, motorway runoff sediments and ashed sewage sludge were normalised against their average crustal abundance to identify characteristic normalisation patterns. With this technique, high Pd concentrations in the River Stour sediments were found to be indicative of sewage inputs. The partitioning of Pt, Pd and Rh was investigated in a novel combination of Tessier’s (1979) sequential extraction technique and a Te coprecipitation. The partitioning in the sediments of a sediment retention lagoon progressed from more to less mobile sediment phases. The PGE are emitted in a form (possibly particulate) that becomes predominantly associated with the silicates fraction. The behaviour of the PGE in the River Stour is predicted to be controlled predominantly by physical processes.