Browsing by Author "Orren, M J"
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- ItemOpen AccessThe analysis of marine algae photosynthetic pigments by high performance liquid chromatography(1984) Bacon, Elizabeth Jane; Orren, M JA 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.
- ItemOpen AccessAnalytical applications of atomic spectroscopy, with particular reference to inductively coupled plasma emission analysis of coal and fly ash(1983) Pougnet, Michel Andre Bruno; Orren, M J
- ItemOpen AccessApplication of an argon-cooled inductively coupled plasma to the analysis of metals in lubricating oils(1987) Marais, Petrus Johannes Jacobus Goosen; Orren, M JA sequential atomic emission spectrometer, using a low power (1,7 kW) argon-cooled inductively coupled plasma (ICP) system, was used for the determination of wear metals and additives in lubricating oils with xylene as solvent. The modified Simplex method was applied to establish the optimum experimental parameters for 21 individual spectral lines. The optimization was applied to single element analysis on the basis of net signal-to-background ratio (SBR) using the standard cross flow nebulizer and then repeated using the high solids Babington-type nebulizer. Weighted compromise conditions were calculated resulting in a maximum loss of 50% in the SBRs of the individual elements. These conditions result in an analytically useful plasma that gives low detection limits and high sensitivities for the analysis of metals in lubricating oils. Analytical parameters such as detection limit and analytical range for the analysis of 17 elements present in lubricating oil as wear metals or contaminants and 4 other elements present in the most common lubricating oil additives were determined. The detection limits reported here for oil in xylene are of the same order as the published limits for aqueous and for oil-in-MIBK solutions. However, the most valuable property of the ICP-AES was found to be the astounding analytical range which allows determinations to be made over a large concentration range without the need for serial dilutions. The effect of sample preparation was investigated by employing ultrasonic agitation prior to withdrawing the used oil from the sample vial. An upward trend was found in the element concentrations from manual shaking of the oil to ultrasonic agitation, indicating a particle distribution effect. Finally, the technique was tested successfully by analysing an NBS reference standard and by participating in several "round robin" used oil analyses. ICP-atomic emission spectrometry can be successfully applied to the analysis of metals in lubricating oils with a speed, accuracy and precision which at least equals, and even improves upon any other of the established techniques.
- ItemOpen AccessThe solvent extraction of CU (II) from chloride solutions with certain non-chelating nitrogen donor ligands(1986) Soldenhoff, Karin; Preston, J S; Orren, M J; Koch, KThe extraction of copper from chloride solutions with some aliphatic oximes as well as some pyridine carboxylates was studied and the complexes formed in the organic phase identified. The association of octanal oxime in toluene was taken into account in the extraction studies and formation constants for dimers and trimers obtained. Copper (II), Nickel (II) and Cobalt (II) are extracted by a solvating mechanism in which only the neutral MCl2 species is extractable. This reaction is largely independent of pH. Studies were also carried out on the use of the commercial reagent ACORGA CLX-20, for the selective extraction of copper from a synthetic solution simulating leach liquors obtained by ferric chloride leaching of complex sulphide ores. Results show that separation of copper from iron is dependent on the amount of acid and chloride present in the aqueous phase.
- ItemOpen AccessVervlugtiging van metale tydens die droging van biologiese materiaal(1976) Fourie, Hermanus Ockert; Peisach, Max; Orren, M JDaar 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.