Full text
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| Author(s): |
Rafael Giovanini de Lima
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2020-07-17 |
| Examining board members: |
Hudson Wallace Pereira de Carvalho;
Renata de Faria Barbosa;
Paulo Sérgio Parreira
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| Advisor: | Hudson Wallace Pereira de Carvalho |
| Abstract | |
The elementary evaluation of the constituents of a sample is of major importance in agricultural and environmental sciences. These analyses can be performed by various methods and equipments. In this context, the total reflection X-ray fluorescence technique (TXRF) is becoming more consolidated due to detection limits in the order of g L-1 or g kg-1, a wide range of linear response, applicability to elements with Z>11, a non-destructive form of analysis, a small amount of samples and low operational cost. This research project proposed the assembly and commissioning of a TXRF system with high power X-ray tube and automatic sample changer. As a result, the execution of this project provides the scientific community with an alternative tool to conventional analytical techniques. This text explains in detail the equipment assembly processes, the adjustments of the moving parts - such as the monochromator and the reflective substrate - and the experiments developed. As validation of the equipment, calibration curves were built for liquid samples, plant tissues and soils. Liquid analyses had detection limits of: 22.3 g L-1 for Fe; 14.7 g L-1 for Ga; and 14.3 g L-1 for Se. Vegetable tissue analyses had detection limits of 856 mg kg-1 for P; 425 mg kg-1 for K; 289 mg kg-1 for Ca; 10 mg kg-1 for Mn; 16 mg kg-1 for Fe; 3 mg kg-1 for Cu; 5 mg kg-1 for Zn; 2 mg kg-1 for Rb; and 4 mg kg-1 for Sr. Soil samples had detection limits of 914 mg kg-1 for K; 313 mg kg-1 for Ca; 254 mg kg-1 for Ti; 114 mg kg-1 for Mn; 69 mg kg-1 for Fe; 15 mg kg-1 for Rb; 19 mg kg-1 for Sr; and 132 mg kg-1 for Th. The linear work ranges for the calibration curves were constantly of the order of 4 to 5 orders of magnitude, except in some cases where the curves were made with certified reference samples that did not cover such a linear range. Finally, comparative analyses were made between soybean sap and nutrient solution, between soybean sap and plant tissue and between plant tissue and reference analyses (AU) | |
| FAPESP's process: | 18/02462-5 - Alignment, coding and commissioning of a total reflection X ray fluorescence (TXRF) system under vaccum and automatic for agricultural and environmental research |
| Grantee: | Rafael Giovanini de Lima |
| Support Opportunities: | Scholarships in Brazil - Master |