Browsing by Author "Santos, Rui Miguel P."
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- Effects of methane addition to nebulizer gas on polyatomic interferents and ion sensitivity in inductively coupled plasma mass spectrometryPublication . Santos, Rui Miguel P.The addition of methane to nebulizer gas was assessed as a method for the reduction of polyatomic interferents in inductively coupled plasma mass spectrometry (ICP-MS). The effects of nebulizer gas flow rate, RF power and methane flow were studied for a range of analytes and polyatomic ions. The analyte sensitivity, especially for Be, Br and I, was enhanced by a factor of 7–12 with methane addition. Polyatomic ions, such as ArCl+, ArO+, ClO+ and ArArH+, were reduced between 61 and 92% when compared to those of an unmodified plasma. Such reduction allowed better quantification limits for V, As, Se, Br and I, as well as 90% BaO+ polyatomic reduction. Finally, the optimized conditions were evaluated in successful recovery tests for As, Se and V in different matrices with high chloride content. The Fe accuracy was evaluated in several reference materials.
- Terras raras nos sedimentos Pliocénicos entre os rios Vouga e Mondego (Portugal) = Rare earth elements in the Pliocene sediments between rivers Vouga and Mondego (Portugal)Publication . Oliveira, Álvaro; Dinis, Pedro A.; Santos, Rui Miguel P.; Rocha, FernandoA geoquímica de sedimentos argilosos do Pliocénico é usada para determinar as principais fases transportadoras de terras raras. Foram consideradas 3 fácies, associadas a sedimentação em planície de inundação e em pântano-lago, e dois sectores. A concentração de terras raras pesadas é substancialmente maior nos sedimentos de pântano-lago que nos de planície de inundação. Ainda que os minerais de argila integrem parte das terras raras, o xenótimo e a monazite são os principais minerais a transportar aqueles elementos. Outras fases (p. ex. matéria orgânica) em sedimentos de pântano-lago devem reter uma parte significativa das terras raras, em particular das terras raras pesadas. As concentrações de terras raras nos dois sectores não são muito diferentes, sugerindo que a proveniência era similar.