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  • Author or Editor: H. Al-Shahristani x
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Abstract  

Several hundred samples of human head hair were analyzed to establish the range and variation of mercury concentration in “normal” people and in persons ingesting organic mercury compounds. Instrumental neutron activation analysis was used. The 77 keV line of197Hg was counted on a Ge(Li) detector. The pattern of concentration variation along hair was shown to be a more reliable criterion for hair individualization than average concentration values. The hair mercury contents of “normal” people in uncontaminated areas were 0.1–4 and 1–12 ppm, respectively. People who had ingested a mercury compound but showed no symptoms had hair mercury concentrations of from a few ppm to 300 ppm. Mild symptoms appeared with a 120–600 ppm hair mercury level, moderate with 200–800 ppm, and severe with 400–1600 ppm. There was no correlation with sex or age, except that infants showed more severe symptoms than expected, and people over 55 had mild or no symptoms with hair mercury levels of 1000 ppm and higher.

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Abstract  

The trace-element composition of crude oil was studied using instrumental neutron activation techniques and a large-volume high-resolution Ge(Li) detector. A total of 29 elements were determined in oils representing the various producing formations of the Iraqi oil fields. These were: Al, Ar, As, Au, Br, Ca, Cl, Co, Cr, Cu, Eu, Fe, Ga, Hg, K, La, Mn, Mo, Na, Ni, Re, S, Sb, Sc, Se, Sm, V, W and Zn. The significance of these trace elements in the geochemical investigation of crude oil is discussed.

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Abstract  

Resonance neutron activation and gamma-ray spectrometry were used to determine traces of iodine in biological materials. The method developed is purely instrumental and fairly rapid. The major interfering activities of24Na,38Cl,36Mn and82Br were significantly reduced by irradiating the samples inside a shield of Cd, NaCl, MnBr2 and MnO2. Neutrons with energies close to the resonances of Na, Cl, Mn and Br were absorbed in the shield and did not activate the sample while neutrons with energies close to the resonances of iodine were not absorbed appreciably. Thus the activity of128I was enhanced relative to the interfering activities. The 442 keV gamma of128I (T=25 min) was measured using a high-resolution Ge(Li) detector and a multichannel analyzer. Sensitivity of 0.05 ppm was obtained.

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Abstract  

A comparative study is made on different activation methods for mercury analysis. Mercury concentrations down to 0.1 ppm were determined instrumentally via the isotopes197Hg (T=65 h) and203Hg (T=47 d). A high-resolution Ge(Li) detector was used in measuring the activity and a small computer for data reduction. Up to 500 samples were measured daily. Chemical separations were performed on samples with low mercury concentrations. Sensitivity of 0.01 ppm was attained by precipitating HgS from basic solutions and counting197Hg on NaI(T1) detector. A new rapid instrumental method was also developed based on199mHg (T=43 min). This short-lived isotope was activated with resonance neutrons. The sensitivity of the method is 0.5 μg and it requires only 1 hr.

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Abstract  

An istrumental method is developed for the determination of As, Br, Cd, I, Mg, Mo, Sb, Si, Sn and Sr in biological materials based on resonance neutron activation analysis. Samples were irradiated inside cadmium and boron shields with reactor neutrons and counted on Ge(Li) detector after a delay of about 5 min. The interfering activities of24Na,38Cl and56Mn were significantly reduced particularly in the boron shield. The advantage factors of the various elements are compared for boron and cadmium shields. The method is especially useful for the determination of As, Cd, I and Sn.

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Abstract  

A method for the continuous on-stream determination of trace concentrations of uranium and thorium in flowing streams is developed. The 14 MeV neutron generator was used for irradiation and the delayed neutron counting technique was employed in counting the induced neutron activity. The dependence of the minimum detectable concentration on the irradiation, decay and counting times, liquid flow-rate and the background was studied. At optimal conditions, uranium and thorium concentrations were determined down to 20 and 100 ppm, respectively. The interference of the neutron emitting nuclide17m O was reduced to an insignificant level by optimizing the decay time.

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Abstract  

The silica gel adsorption behaviour of zirconium, niobium, ruthenium and cerium in hydrochloric acid has been investigated by batch and column techniques. A satisfactory radiochemical separation of zirconium and niobium from each other and from other fission products has been achieved by a two column technique. The recommended procedure consists of sorption of all the nuclides on a primary silica gel column. Fifteen per cent of95Nb, all of the zirconium and all of the other fission products are eluted first by washing with 5.5 M HCl. A second elution with concentrated hydrochloric acid then recovers the95Nb (free from other products). The solution from the first elution after evaporation to 1 ml is then passed through another silica gel column and successively washed with 0.5M HCl, 5.5M HCl and concentrated HCl to obtain three fractions—other fission products—95Zr free from other products—95Nb free from other products, respectively.

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