Includes bibliographical references. / Daar bestaan verskeie analitiese tegnieke vir die kwantitatiewe bepaling van spoorelemente in biologiese materiaal. Om elke tegniek aan die gevraagde vereistes van sensitiwiteit, reproduseerbaarheid en akkuraatheid te laat voldoen, word gebruik gemaak van gespesialiseerde instrumentasie. Met biologiese matryse verg die meeste van hierdie metodes egter 'n voorbereidende ontbindingsprosedure om die organiese materiaal af te breek. Dit impliseer droging gevolg deur droe of nat verassingsprosedures van die materiaal. Die vraag ontstaan egter of geakkumuleerde metale, deur organismes gemetaboliseer word tot vlugtige organiese verbindings, en indien wel, of dit die huidige, algemene analitiese metodiek wat gebruik word, enigsiens kan beinvloed. Aan die hand van mariene organismes, word in hierdie studie die radionukliedes van die elemente kroom, mangaan, yster, kobalt, sink, arseen, selenium, kadmium, antimoon en lood gebruik om 'n bydrae te lewet tot die begrip van metaboliese prosesse, en terselfdertyd lig te werp op die betroubaarheid van die analitiese tegnieke wat toegepas word.

Bibliography: leaves 91-95. / The effect of SnCl₂ on the solvent extraction of K₂PtCl₄ in HCl into CH2Cl2 using triphenylphosphine (PPh₃) has been studied in detail. It has been found that SnCl₂ dramatically increases the rate and efficiency of extraction. Our studies show that the percentage Pt extraction depends upon the time allowed for extraction, the Pt(II)/PPh₃ ratio, the Pt(II)/Sn(II) ratio and the HCl concentration in a complicated way.

Bibliography: p. 73-74. / The organic ligands 5- and 7- methyl-8-hydroxyquinoline have been synthesised and shown to form green, water soluble, 1:1 complexes with iron(III) and thus to possess the same composition as the complexes with 8-hydroxyquinoline and 2-methyl-8-hydroxyquinoline previously reported. Thermodynamic formation constants for the 1:1 complexes of 2-, 5- ,and 7-methyl-8-hydroxyquinoline with iron(III) have been determined -1 3 spectrophotometrically as 5.5. x 10¹⠴, 2.9 X 10¹⠵ and 3.6 x 10¹⠵ mole-¹ dm³ respectively at 25.0°C and I = 0.1M. When compared with the value 8.5 x lO¹⠴ for 8-hydroxyquinoline itself the results support the theory that methyl substitution affects the stability of these complexes by increasing the basicity of the nitrogen atom. The lesser stability of the 2-methyl complex, however, indicates an opposing steric effect of a bulky substituent in the 2-position.

Bibliography: pages 157-165. / A method of analysis of the photosynthetic pigments of in vitro algal cultures, using reverse-phase high performance liquid chromatography (HPLC) is described. This technique was extended to analysis of photosynthetic pigments in samples from the SIBEX-I Expedition; a preconcentration technique was developed to allow a reduction in sample volume for waters of low productivity. HPLC analysis allows accurate chlorophyll a determinations to be made in the presence of the spectrally similar chlorophyllide a, which has been found to be the major chlorophyll a breakdown product present in natural waters. Comparative studies with the SCOR-UNESCO method have shown that as a result of chlorophyllide interference the chlorophyll a concentrations are in fact over-estimates to varying degrees depending on the productivity of the biomass. In addition, quantification of chlorophylls b and c and the carotenoid complement allows identification of the major algal species present, and provides an indication of the physiological status of the bloom.

Abstract not available

The development and evaluation of some new procedures for the determination of various chemical forms of aluminum, mercury, selenium, and sulfur are described in this dissertation. Studies of the biological and environmental transformations of elements are underpinned by the provision of reliable information about the relative concentrations of various chemical forms of the elements. Here, the final measurements were made by graphite furnace atomic absorption spectrometry (GFAAS), cold vapor atomic absorption spectrometry (CVAAS), molecular emission spectrometry (MES) and atomic fluorescence spectrometry (AFS). These measurement techniques were preceded by selective chemical reactions based on liquid-liquid extraction (LLE), chemical vapor generation (CVG) [in particular, hydride generation (HG)] and selective redox chemistry. For the selenium and sulfur speciation techniques, the atomic fluorescence instrument was adapted to monitor molecular sulfur emission and selenium fluorescence simultaneously through two of the instrument's channels. The analyte elements in a sodium tetrahydroborate matrix were merged with a hydrochloric acid stream in a flow-injection manifold, chemical vapor generation was used to introduce the analytes into an argon-hydrogen diffusion flame in the form of hydrogen selenide and hydrogen sulfide. A speciation procedure was developed based on the reactivity towards borohydride at low acid concentrations and the amalgam trapping of both mercury and methylmercury hydride. Spectroscopic discrimination between the methylmercury and inorganic mercury was made by using an amalgam trap. When the amalgam trap was bypassed, no signal for methylmercury was observed. This method was applied to the determination of inorganic and methylmercury in river water tap water, and urine matrices. Validation was performed by analysis of the standard reference materials TORT-2, DOLT-2 and DOMR-2 CRMs. An automated flow-injection approach for the speciation of aqueous aluminum species in waters is suggested. It is intended that the flow-injection manifold be used to identify three types of aluminum; acid reactive (Alr), labile monomeric (Ala) and nonlabile monomeric (Alo). Initial results have been obtained for flow-injection liquid-liquid extraction interfaced with GF-AAS. (Abstract shortened by UMI.)

Abstract not available

No description available.

No description available.

No description available.