The determination of trace iron(II) is' usually interfered by the presence of iron(Ill) when ortho-phenanthroline colorimetric method is used. In this report a chromogenic reagent which contain'S onho-pbenantnroline-Blj'I'A mixture has been developed to decrease the interference of ferric ion after adjusting the acidity of sample at 0.1 N by adding the sulfuric acid. .The procedure -is also simplified by introducing sulfamate buffer solution (pH == I.S) without adjusting the acidity of sample with 'Sulfuric acid. If iron(I1l) is not present in the sample. this method is also applicable. The comparative results are exhibited for the present method and the conventional o-phenanthroline method.
The internal-reference method proposed previously has been applied to the photon-activation analysis of niobium using molybdenum as the reference element. For the determination of niobium, 92mNb produced by the (γ,n) reaction was utilized and 95mNb or 96Nb activities coming from molybdenum by the (γ,p) processes were used as reference. A series of molybdenum and niobium mixtures with known compositions were irradiated by bremsstrahlung photons with a maximum energy of 17 MeV for an hour. After niobium activities were separated chemically, their γ-ray spectra were measured with a lithium-drifted germanium detector. A good proportionality was obtained between the activity ratio, RA0, and the weight ratio, RW. Niobium down to 5μg can be determined with a relative error within ±3% under the present experimental conditions.
A method for the determination of zirconium has been studied by activation analysis with bremsstrahlung photons, with molybdenum used as the internal-reference element. This method is based on the γ-ray spectrometric measurement of the 89Zr activity produced by the 90Zr(γ,n) reaction and on the comparison of this activity with the 88Zr activity formed by the (γ,α) reaction on molybdenum. The reaction products and their rates of production in zirconium and in molybdenum have also been examined as functions of bremsstrahlung maximum energies up to 60 MeV, and the best conditions for the determination of zirconium are proposed. When the maximum energy was set at 20 MeV, no interfering reactions occurred; under the present experimental conditions, a zirconium content down to about 18 μg can be determined accurately. The reliability and the versatility of this method are demonstrated.
An internal‐standard method1–4) has been applied for the determination of La, Sb, Au, Cr and Ag in silicon single‐crystal by neutron activation analysis using cobalt as an internal‐standard element. No chemical separation is required in this case and the precision obtained with the present method is satisfactory.
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