Comparison of analytical methods for the determination of trace amounts of strontium and yttrium by photon induced X-ray fluorescence techniques in lateritic materials |
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Authors: | J J LaBreque E Marcano C A Peña W C Parker |
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Institution: | (1) Instituto Venezolano de Investigaciones Cientificas-IVIC, Apartado 1827, 1010A Caracas, (Venezuela) |
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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.
This project was funded by Consejo Nacional de Investigaciones Científicas y Technológicas (CONICIT) and performed as part
of UNESCO's IGCP-129 “Lateritization Processes” project. |
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