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Date of Award

3-1989

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Supervisor

Professor A. Corsini

Abstract

A method has been developed for the direct determination of mercury in aqueous samples using electrothermal atomic absorption spectroscopy (AAS). This method is based on the thermal stabilization of mercury on the surface of a gold-plated graphite tube during the heating cycles of the furnace. The effect of various parameters such as charring and atomization temperatures, acid strength, presence of other metal ions and complexing agents was examined. Based on these investigations, optimal conditions for the determination of mercury at trace levels were established.

The method provided a detection limit of 0.07 ng of Hg and was found to be faster and simpler than other available techniques. In addition, the method is well suited to the determination of mercury in samples that have been preconcentrated for multielement determination.

The mechanism of thermal stabilization on the surface of gold-plated tubes and platforms was studied. Likely reactions are the reduction of mercury(II) from solution and the formation of a mercury-gold amalgam on the surface of the gold layer. Two forms of stabilized mercury were observed; one form at the surface which began to atomize above 300°C and another form dissolved in the gold which began to atomize above 1400°C.

The gold-plated tube AAS technique was used to study the retention and elution behaviour of mercury on a column of the macroporous resin, XAD-7, for the purpose of enrichment (i.e., preconcentration) of mercury from natural waters. The effect on retention of parameters such as pH and the nature of the mercury species was investigated. For the elution of mercury from the column, several parameters were examined, the most important being solvent strength, which governs the magnitude of the preconcentration factor. The system was then applied to the preconcentration, speciation and measurement of mercury in synthetic water samples.

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