Browsing by Subject "Analytical Science"

Now showing 1 - 8 of 8
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    The analysis of marine algae photosynthetic pigments by high performance liquid chromatography
    (1984) Bacon, Elizabeth Jane; Orren, M J
    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.
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    Complexes of iron (III) with derivatives of 8-quinolinol
    (1981) Golden, Corinne Ellen; Irving, H M N H
    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.
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    The development and testing of a fault-tolerant series resonant distribution network
    (2004) Cross, Nicola; Gaunt, C Trevor
    Includes bibliographical references.
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    The effect of stannous chloride on the solvent extraction of tetrachloroplatinate(II) ion by triphenylphosphine
    (1981) Yates, Janet Elizabeth; Koch, Klaus
    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.
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    Flux of cadmium through a laboratory food chain (media-algae-mussel) and its effects
    (1981) Hennig, Helmke F-K O; Irving, H M N H
    The increasing pollution of the aquatic environment by cadmium is a potentially severe problem and techniques are needed to document the effect of the metal. To investigate the flux of this metal through a laboratory food chain, algae were grown in various cadmium concentrations for subsequent use as contaminated food for mussels. The results showed that in order to make valid deductions, more information about chemical mechanisms and background ecophysiological data is needed, otherwise accumulation reports may become misleading. It was found that the best growth and accumulation results were achieved by harvesting algae from a zinc deficient media containing 7 μmole dm-3 cadmium and at a particular life cycle phase. Two uptake mechanisms are proposed. These "contaminated" algae were fed to mussels under different accumulation regimes. The metal gain and loss were determined and compared to a "baseline" dry body weight which had been calculated from a shell length-body weight relationship. Cadmium accumulation took place in the mussels and after some initial delay, could be correlated to weight loss. Such a weight loss was due to pathological and biochemical changes in the mussels. It was shown that the toxic effect of cadmium could be determined much earlier by the presence of special proteins. The elutant profiles of the gel chromatography study showed the production of metal binding protein as well as a spill over of cadmium into the enzyme pool, caused by a higher uptake than elimination rate. Cadmium on metal binding protein and in the enzyme pool could be related to the poisoning effect of the metal and a pollution history for the mussels identified. The characteristics of the metal binding protein were found to be very similar to those reported for metallothionein and had an approximate molecular weight of 10 600 daltons.
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    Structural and spectroscopic studies with dithizone and its derivatives
    (1980) Hutton, Alan T; Irving, H M N H
    An X-ray crystal structure detennination of 3-nitro-l,5-di(2,6-dimethylphenyl) fonnazan, ArN:N•C(N02):N•NHAr (Ar= 2,6-dimethylphenyl), has shown that the N-N-C-N-N chain is stabilized by an unusual hydrogen bond in the closed-ring syn,s-cis configuration relative to the formal double C=N and single C-N bonds. The bond lengths reveal complete n-electron delocalization along the chain which results in a mesomeric structure; the possibility of such a mesomeric structure existing in solution rather than a rapid tautomeric equilibrium between two limiting forms of the resonance hybrid has been considered in the light of i.r. and n.m.r. spectroscopic measurements. The temporal changes in the visible absorption spectrum of S-methyldithizone, PhN:N•C(SCH3):N•NHPh, have been shown to arise from syn-anti isomerization about the fonnal C=N double bond and rotation about the C-N single bond by considering the evidence provided by i. r. and n.m.r. spectroscopic studies combined with the X-ray crystal structure of the di(o-tolyl) homologue. The parent compound dithizone, PhN:N•C(SH):N•NHPh, previously thought to exist as an equilibritim of thiol and thione forms in solution has now been shown to consist of a single species in solution mainly by consideration of its n.m.r. spectroscopic properties. Organomercury(II) complexes of dithizone have been shown to be photochromic in solution; X-ray crystal structure detenninations of phenyland methylmercury(II) dithizonate, besides revealing rare three-coordination of mercury, have been combined with spectroscopic measurements on the normal and activated fonns to reveal the structure of the labile photo-isomers.
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    Towards the separation of linear α-olefins from industrial process streams using transition metal stationary phases
    (1994) Phaho, David Sekgweng; Koch, Klaus R
    The use of silver modified stationary phases for the separation of olefins from hydrocarbon mixtures was investigated. Gas solid chromatography (GSC) was found to be a quick and efficient technique for screening ion exchange resins and zeolites as potential support materials in olefin separation. Using GSC, the efficiency of Ag⁺ exchanged resin in retaining olefins relative to alkanes in a given mixture was found to be dependent on the porosity of the resin used. The silver form of the porous, macroreticular type Amberlyst A-15 resin strongly retained olefins in the GC column as compared to the microporous Amberlite IR(120) resin. Olefins were so strongly retained on the Ag⁺exchanged Amberlyst A-15 resin that they could only be eluted efficiently from the GC column at elevated temperatures. The Ag⁺ exchanged resin was however found to undergo degradation at elevated temperatures (> 140⁰C) and hence the resin packed columns could not be re-used.
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    Vervlugtiging van metale tydens die droging van biologiese materiaal
    (1976) Fourie, Hermanus Ockert; Peisach, Max; Orren, M J
    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.