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Título: DETERMINATION OF MAJOR, MINOR AND TRACE ELEMENTS IN ROCK SAMPLES BY LA-ICPMS AFTER TARGET PREPARATION BY FUSION WITH LITHIUM BORATES
Autor: TACITO DANTAS FROTA LEITE
Colaborador(es): NORBERT FRITZ MIEKELEY - Orientador
CARMEM LúCIA PORTO DA SILVEIRA - Coorientador
Catalogação: 02/AGO/2006 Língua(s): PORTUGUESE - BRAZIL
Tipo: TEXT Subtipo: THESIS
Notas: [pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio.
[en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio.
Referência(s): [pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=8759&idi=1
[en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=8759&idi=2
DOI: https://doi.org/10.17771/PUCRio.acad.8759
Resumo:
Determination of trace elements in rock samples by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) has become an important tool for investigations in petrogenesis, metallogenesis and ore prospecting. However, despite the availability of new generation lasers with shorter pulse duration (fs) and wave length (<266 nm), calibration remains still a critical issue when matrixmatched standards are not available. One of the most serious non- spectral interference in LA-ICPMS is chemical fractionation, which causes compositions of standard and sample and their respective ablated masses to be different, thus compromising accuracy and precision of the results. When bulk analysis is the main objective, matrix matching can be achieved by the simple fusion of samples and standards with meta/tetraborates fluxes, similar to what is routinely used in XRFA. This work reports on our experience with this procedure in the analysis of basaltic rocks, aiming at the trace element characterization of host rocks from oil exploration sites in Brazil. The experiments were performed with a CETAC LSX- 100 laser ablation system (Nd:YAG, 266 nm, operated in the Q-switched and scanning mode) coupled to an ELAN 5000 ICPMS. An argon- nitrogen mixture (2 % N2, 98 % Ar) was used as carrier gas to enhance the mass of material ablated, thus increasing signal intensities and reducing detection limits. A cyclonic spray chamber was arranged just before the ICP-torch as a tentative to uniform aerosol particle size for improving measurement repeatability and robustness of the plasma. For comparison, the system was also operated without a spray chamber. Calibration samples were prepared from two standard reference materials: NIST SRM 688 basalt and NIST SRM 278 obsidian. The powdered rock standards were mixed and homogenized with a lithium borate flux (CLAISSE, pure, 75 % Li2B4O7, 25 % LiBO2) using rock-to-flux mass ratios of 1:5, 1:11, 1:23 and 1:47, respectively, thus obtaining each standard in four different analyte concentrations. Indium was used as an internal standard (IS) and was added before fusion to achieve targets with IS concentration of 100 mg kg(-1). Blanks from the lithium borate flux were produced in a similar way. Method validation was performed with GSJ basalt JB-2 and NIMG granite SARM-1, prepared at a constant sampleto- flux mass ratio of 1L:5 and containing also the IS. All fusions were performed in an automated furnace (CLAISSE Fluxy). Solution nebulization ICP-MS/OES after dissolution of smaller target pieces in HNO3 was used to assess for volatilization losses. Forty elements were determined and good linearity of the calibration curves was obtained and for most of them the correlation coefficient (R2) was higher than 0.995. Detection limits ranged from 0.013 mg kg(-1) for Tb to 0.6 mg kg(-1) for Zn, and improved for several elements by using a cyclonic spray chamber (e.g. V, Zn, Rb, Y, Nb, Ba, Ce, Sm, Tb, Dy, Ho, Tm). In the analysis of GSJ basalt JB-2 and NIMG granite SARM-1, accuracy was better than 5 % for: V, Sr, Y, Ba, Ce, Nd, Yb, and Lu; between 5-10 % for: Sc, Zn, Rb, Tm, and 10-20 % for: Co, Zr, La and Tb. Repeatability was better than 5 % for: V, Rb, Sr, La, Nd, Ta, between 5-10% for: Sc, Co, Zn, Y, Zr, Ba, Tb, Yb, and 10-20 % for: Ce, Tm, Lu and Hf. Additionally, the semiquantitative TotalQuant II calibration was applied, which gave, within the expected uncertainty for this calibration method (10 % to 20 %), concordant results when compared to the quantitative external calibration procedure. Preliminary results on the application of these methods for the determination of trace elements in basaltic host rocks from oil exploration sites will be shown.
Descrição: Arquivo:   
COVER, ACKNOWLEDGEMENTS, RESUMO, ABSTRACT, SUMMARY AND LISTS PDF    
CHAPTER 1 PDF    
CHAPTER 2 PDF    
CHAPTER 3 PDF    
CHAPTER 4 PDF    
CHAPTER 5 PDF    
REFERENCES AND ANNEX PDF