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  • Author or Editor: E. Marcano x
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Abstract  

An improved method for the determination of ruthenium in catalytic materials based on a relative fluorescence ratio factor is presented. This method employs a thin-film technique and an internal standard technique to minimize absorption and enchancement effects. The samples and standards were fluorescent with a109Cd (7 mCi) annular source for 200 seconds and the data were collected and analyzed with an Apple II+ micro computer. Precision (total variation) for typical ruthenium catalysts in the range of 1–5% ruthenium was about 2%. Finally, the concentration of ruthenium in six commercial catalysts was determined for both alumina and carbon supports.

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Abstract  

The comparison of an ambient temperature mercuric iodide spectrometer (HgI2) with a conventional cooled Si(Li) spectrometer is presented for the determination of niobium in Venezuelan laterites in the laboratory. The energy resolution of the HgI2 spectrometer was only about 590 eV (FWHM) at 5.9 keV compared to about 150 eV for the conventional Si(Li) spectrometer. The efficiency was about 5 times lower in the region of the NbK peak as compared to the Si(Li) detector. Even though its energy resolution and efficiency is much poorer than the conventional Si(Li), the results it produced for the determination of niobium were acceptable for use in the exploration and exploitation of a niobium-rich deposit such as Cerro Impacto, Estado Bolívar, Venezuela.

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Abstract  

A rapid radioisotope induced energy-dispersive X-ray fluorescence procedure for the simultaneous determinations of Cobalt, Nickel and Molybdenum in hydrodesulfurization catalysts is presented. A109Cd (7 mCi) source is used as the excitation system coupled to a high resolution Si(Li) detector. A PDP-11/05 processor is employed as a multichannel analyzer and also to automatically control the complete system by means of a prewritten computer program. The relative standard deviations for the three determinations (CoO, NiO and MoO3) are less than 5% for 300 seconds of fluorescent time for a typical sample. Finally a comparison of results by different methods is given to check the accuracy since no standard reference materials are available for catalytic material.

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Abstract  

Three different analytical methods for the determination of strontium and yttrium in Venezuelan latterites by radioisotope induced X-ray fluorescence are compared, also with results from conventional wavelength dispersive X-ray fluorescence. The samples analyzed were from Cerro Impacto, Venezuela. The photon-induced energy dispersive X-ray fluorescence system consisted of a109Cd (7 mCi) source for excitation of the characteristic K X-rays for strontium and yttrium. The detection system employed a high resolution Si(Li) detector and was completely controlled by a PDP-11/05 processor. Of the three analytical methods described, the internal standard-thin film technique was shown to be slightly superior to the conventional standard calibration curve method and the standard additon/dilution procedure. This can be explained by considering the effectiveness of the compensation of the sources of errors by these methods. It should also be noted that in the case of wavelength dispersive X-ray fluorescence, an about 5–10 times greater sample is needed, which is a limitation compared to energy dispersive X-ray fluorescence in some cases. Finally, typical relative standard deviations of the energy dispersive X-ray fluorescence methods were about 10–15% for the range of about 100–100 ppm of strontium and yttrium; these values are acceptable considering the large degree of heterogeneity in this type of geological material.

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