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Gewählte Master / Diploma Thesis:

Enrico Porotti (2018): Development, validation and uncertainty balance of an ICP-OES method for quantification of plant available and amorphous silicon in arable land and grassland soils of Austria..
Master / Diploma Thesis - Institut für Bodenforschung (IBF), BOKU-Universität für Bodenkultur, pp 75. UB BOKU obvsg

Data Source: ZID Abstracts
Silicon is the second most abundant element in Earth’s crust and it is known to increase the resistance of plants to pests and abiotic stress factors alike. Most research has focused on plant physiology and genetics linked to silicon, while in-depth knowledge of silicon in soil is lacking. In this regard there are two main concerns. On one hand, all certified reference materials that include Si concentration, report only the total Si concentration, with no information regarding the different fractions of soil silicon; on the other hand, there is a lack of deeply described methods for quantification of Si in solution. The aim of my thesis is to address this latter issue, with a focus on quantification of Si in 0.01M CaCl2 and 0.2M NaOH soil extracts. An ICP-OES method is developed as a potential alternative to spectrophotometry. The parameters considered include RF power, Z-position of the plasma torch, wavelength, viewing distance and rinsing time. The selection of optimal method parameters is based on BEC, LOD and LOQ, R2, %RSD of measurements performed on standard solutions. Also, external standard and standard addition are compared on soil samples with different SOM and lime content and pH, in order to assess the existence of a matrix effect on Si measurements and to estimate analyte recovery. In addition to parameters of the ICP-OES instrument, variations to the extraction methods are tested, specifically, the speed at which soil samples are shaken during extraction and the separation of the extract from the suspended soil sample. In this regard the novel ICP-OES methods are compared to a colorimetric method developed in-house from well-established absorptiometric methods for quantification of Si. Finally two uncertainty budgets, one for the concentration of silicon estimated from ICP-OES measurements and one for the absorptiometric measurements, are proposed and their application to the measurements taken in this study is reported.

Beurteilende(r): Wenzel Walter

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