Development of Novel Oxidation Catalysts for Carbon Isotope Ratio Analysis

Fomes, Charles William (2001). Development of Novel Oxidation Catalysts for Carbon Isotope Ratio Analysis. PhD thesis The Open University.



The International Rosetta Mission is the name given to the European Space Agency’s bold plan to perform in-situ analysis of a comet. One of the instruments on board, MODULUS, is a Gas Chromatograph - Mass Spectrometer that will use the concepts of chromatography and chemical oxidation to return data on chemical composition, and the carbon isotope ratios of the components of the comet The requirements of the chromatographic columns and oxidation catalysts are severe. The issues of mass, power and stability at launch were concerns for the integration and functionality of the instrument at the comet surface.
The unique nature of the analysis system required that a laboratory analogue of the device to be designed and constructed, so that potential components could be tested using an instrument similar to MODULUS. Once developed, the laboratory system allowed performance testing of four chromatographic columns, as well as observing the effect of space qualification (vibration) testing of those columns. Results allowed recommendations of column choice to be passed to the MODULUS science team.
Traditionally, oxidation units for isotope ratio analysis consist of oxides of nickel and copper, which operate at high temperatures (800-1000°C) and therefore would draw large amounts of power if used on MODULUS. Compounds that potentially are more efficient were examined, created and tested (using the MODULUS laboratory analogue) for the replacement of such compounds. Oxides of rhodium, palladium and copper-chromium were found to preserve sample isotope integrity, oxidise efficiently, and work at far lower temperatures (<500°C) than the traditional materials.
As an application for techniques developed for MODULUS, a new method was created for analysis of 813C in terrestrial atmospheric CH4. The method was tested using headspace samples of air from wetlands in Finland and Scotland. An experiment was devised to observe any 813C shift induced by the addition of sulphate to wetland soil and change in incubation temperature. No significant relationships between 813C of CH4 and incubation conditions were found.

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