Browsing by Author "Ahrens, L H"

Now showing 1 - 7 of 7
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    Atomic absorption spectrometry and its application in geochemistry
    (1968) Butler, Louis Robert Patrick; Ahrens, L H
    The atomic absorption method of analysis is reviewed. The theory describing the various phenomena such as atomic population, spectral line shapes, factors influencing absorption, analytical graph curvature, etc.are deduced. The practical aspects of atomic absorption are discussed with respect to: Instrumentation: flame studies and an attempt to develop "a universal" flame; contamination; sources of errors, etc. The method is applied to the analysis of silicate materials. Problems of sample dissolution and standards preparation are discussed. Applications have been made on the determination of the alkali metals (including lithium isotope determination), magnesium and calcium, copper, zinc, iron, manganese, molybdenum and aluminium. Although certain geochemical aspects of these elements are discussed, the analytical problems are stressed. The interference effects by other elements were tested and techniques developed to enable interferences to be overcome. It is concluded that atomic absorption spectrometry has significant uses for the geochemist, especially for the estimation of elements of the trace and minor concentration levels.
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    An investigation of the combined use of cation exchange enrichment and spectrochemical analysis for the determination of trace constituents in common silicate rocks and chondrites
    (1960) Edge, Robert Arthur; Ahrens, L H
    The combined use of cation exchange enrichment and spectrochemical analysis has been investigated for determining trace constituents (particularly caesium and the rare earths) in common igneous rocks and chondritos. Cation exchange chromatography with hydrochloric acid elution was employed to resolve the complex mixtures obtained from rocks and meteorites into a number of fractions in which the concentration of various trace constituents were above their spectrochemical detection limits; the trace constituents are not required in a highly concentrated form. These elements may then be determined spectrochemically. Before developing suitable column procedures for the enrichment of trace constituents, the sequence with which both major and trace constituents of common igneous rooks and chondrites moved through cation exchange columns on elution with various concentrations of HCl were established. Perchloric acid was also investigated as an eluant. The spectrograph was used to monitor the effluent fractions obtained from the cation exchange columns. Suitable column conditions were then developed for concentrating several trace elements for spectrochemical analysis.
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    Low-level alpha and gamma radioactivity in some naturally occurring samples
    (1964) Cherry, Robin David; Ahrens, L H; Schaffer, W
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    The reaction between ferrocytochrome c and hydrogen peroxide
    (1968) Hulett, Leslie Graham; Ahrens, L H; Erlank, A J
    The reaction between ferrocytochrome c and hydrogen peroxide has been studied to determine possible reaction mechanisms. This was done by investigating the effect of various physical factors, such as hydrogen ion concentration, ionic strength and temperature, on the reaction and by studying the kinetics of the reaction. The study of pH and ionic strength showed that an ionization occurred at pH 7.8 which influenced the reactivity of the cytochrome c. The reaction was studied kinetically at pH 8.1 and pH 6.6. At pH 8.1 simple kinetics showed an uncomplicated reaction between ferrocytochrome c and hydrogen peroxide. The kinetic studies at pH 6.6 showed that ferrocytochrome c, hydrogen peroxide and ferricytochrome c (acting as a product catalyst) were involved in the reaction. The product catalysis complicated the kinetics and difficulty was experienced in fitting a suitable reaction mechanism. Copper ions have been found to catalyse reactions similar to that studied here. The effect of a copper histidine complex was therefore investigated on the reaction at pH 8.7. The copper complex was found to catalyse the oxidation of ferrocytochrome c by hydrogen peroxide and the kinetic studies of this oxidation showed that the reaction could be fitted to a simple mechanism which did not involve the formation of intermediate complexes. An unusual feature of the reaction was the ability of the cytochrome c, after complete oxidation, to undergo reduction, which is dependent on the presence of both hydrogen peroxide and copper ions.
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    Some aspects of the geochemistry of Kimberlite xenocrysts [Microfiche]
    (1974) Lawless, Patrick Joseph; Ahrens, L H; Gurney, J J
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