試料溶液の重量採取と中性子放射化γ線スペクトル法の組み合わせによるナノグラム量ユウロピウムの高精度定量

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The precision of the determination of nanogram quantities of europium was increased greatly through the gravimetric sampling of standard and sample solutions. About 3 mg(≈0.003 ml) of europium solutions (1100 μg-Eu/ml) was weighed out by means of a polyethylene pycnometer (Fig. 1) and spottes on a piese of filter paper (0.5 cm in diameter). The filter paper was dried at room temperature and sealed in a polyethylene pouch. The sample was irradiated, together with a standard in a pneumatic tube of JRR-2 at a neutron flux of 7.0×1013 neutron·cm-2·sec-1 for 1 minute. 151Eu (natural abundance 47.77%) is nuclearly trasformed through 151Eu(n, γ) 152mEu to 152Eu, which decays as 152mEu β-, γ(0.842 MeV, 0.961 MeV)→T1/2:9.2h 152Eu β-, γ→T1/2:12.7 years 152Gd The radioactivity of 152mEu was measured by a high resolution Ge(Li)-detector and 1024 channel pulse height analyzer. The repeatability precision of the method was 0.418% in terms of coefficient of variation for 4ng of europium, this value being higher than theoretical precision calculated from statistical fluctuation. The corresponding values were 2.3% and 5.20%, when a 1-ml pipette and a 10-μl microsyringe were used, respectively, for the sampling. The adoption of the gravimetric sampling and activation γ-ray spectrometry allowed the determination of nanogram quantities of europium with an error of 0.5% or less. The procedure was applied to the test of local distribution of europium in red phosphors (europiumdoped yttrium oxide). About 0.5 mg of the sample powder was weighed by a semi-micro balance, transfered to the weighed "weighing vial", then dissolved in 5 ml of 2 M HNO3, and the weight of the solution was determined. About 1 ml of the solution was introduced into a pycnometer, and europium was determined according to the above-described procedure. This experiment revealed that the doped europium was not uniformly distributed in commercial red phosphors from a microscopic point of view.
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試料溶液の重量採取と中性子放射化γ線スペクトル法の組み合わせによるナノグラム量ユウロピウムの高精度定量

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