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  • Author or Editor: M. Guillaume x
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Abstract  

Increasing interest is devoted in geochemistry to the determination of minor elements in rocks and minerals with the best analytical precision. The use of different methods is quite useful to point out and overcome the systematic and specific interferences of the geological matrix. 14 MeV neutron activation analysis can be used for such a purpose as an additional check method. A successful attempt has been made in the determination of rubidium in different geochemical standards. A sensitivity of 100 ppm can be reached with a 5% precision without any interference problem.

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Abstract  

The fixation behavior of PbS specially prepared for analytical purposes has been studied using batch equilibration technique and chromatographic columns. This inorganic adsorbant shows a high and specific fixation capacity for ions such as Cu2+, Hg2+, Br SeO 4 2− . An interpretation of the fixation mechanism is proposed.

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Abstract  

A fast and precise method of determining fluorine in geological matrices is proposed. The 0.20 MeV photopeak of19O, induced by the19F(n, p)19O reaction, was used for this assay. Neutron flux monitoring was achieved by adding an internal standard monitor (20 mg Ce) to each sample and counting the activity due to the 0.74 MeV photopeak of139m Ce, produced in the140Ce(n, 2n)139m Ce reaction. This activity was considered to be proportional to the neutron flux during the sample irradiation. This method of fluorine determination was checked on two fluorine geological standards, mica and apatite, containing 1.50 and 2.90% fluorine, respectively. The sensitivity of the method, obviously depending upon the matrix composition, was 1.46 mg for the mica standard.

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Abstract  

The use of 2.8 MeV neutrons produced by the D(d, n)3He reaction should be taken into consideration in some applications of radioactivation analysis. The low number of elements activable by these neutrons makes possible to minimize the matrix interference and the background below the characteristic photopeaks. The very low dead-time of the spectrometric measurements permits the use of the maximum neutron flux available now and in the future. The purpose of this paper is to define experimentally the sensitivity of determination for the 16 main elements activable with a 400 keV Van de Graaff accelerator at a 2.8 MeV neutron flux of 2·106 n·cm−2·sec−1 on the sample.

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Abstract  

Selenium and tellurium isotopes formed by thermal neutron irradiation have longer half-life than the copper isotope. The non-destructive analysis fails even after the complete decay of copper because of the other radioisotope present. The radioisotopes were separated by ion exchange chromatography on Dowex 1X8 (200–400 mesh) and “Pertitanic” resins in order to obtain a highly sensitive analysis. The limits of detection of 5 ppb for tellurium and 0.5 ppb for selenium were obtained.

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