In a 2003 study of the determination of Iodine in thyroids in Europe to test for
ID: 1034286 • Letter: I
Question
In a 2003 study of the determination of Iodine in thyroids in Europe to test for residual effects from the 1986 Chenobyl explosion, the 129I/127I ratios in sheep and human thyroids were determined as follows. Thyroid extracts were weighed, transferred to a quartz ampoule (10-mm diameter and 50-mm length), and dried at 70?80 ºC. Sealed sample and standard ampoules were irradiated at a thermal neutron flux of 4 x 1013 n.cm¯2.s¯1 for 6.0 h. After 10–15 h decay, the quartz ampoule was broken under a solution containing 30 ml of deionized water, 2 ml of 0.3 mol L¯1 KHSO3, 10 mg Br¯ and 20 mg I¯ in a beaker. Then 3 ml of 1.0 mol L¯1 HNO3 was added to the beaker to dissolve the irradiated sample. Iodine was purified by three cycles of extraction with CCl4 and back-extraction with KHSO3 solution. A portion (2–5 ml) of PdCl2 solution (15 mg Pd2+ ml¯1) was added into the back-extracted aqueous phase; the precipitated iodine as PdI2 was separated by filtering through a Millipore filter. The precipitate with filter was sealed in a polyvial for measurement and the ??rays of 536 keV of 130I produced from 129I and of 388 keV of 126I produced from 127I were counted using a high purity Ge semiconductor detector.
Is this an example of:
Instrumental neutron activation analysis.
Chemical neutron activation analysis.
Radiochemical neutron activation analysis.
Particle induced gamma ray emission analysis.
14 MeV fast neutron instrumental neutron activation analysis.
a.Instrumental neutron activation analysis.
b.Chemical neutron activation analysis.
c.Radiochemical neutron activation analysis.
d.Particle induced gamma ray emission analysis.
e.14 MeV fast neutron instrumental neutron activation analysis.
Explanation / Answer
Answer: a. Instrumental neutron activation analysis.
ampoules were irradiated at a thermal neutron flux of 4 x 1013 n.cm¯2.s¯1 is carried out in Instrumental neutron activation analysis (INAA), or sometimes referred to as simply NAA, is a method for determination of many elements at low levels in a given sample. The method is based on neutron activation and therefore requires a source of neutrons. The nuclides of 129I and 127I are determined by gamma ray spectroscopy using a high-resolution germanium detector.
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