Determination of inorganic impurities in PVC latex by activation analysis

Experimental work was carried out in order to determine inorganic impurities in PVC latex by activation analysis. Arsenic and bromine were detected and quantitatively determined by means of two alternative methods: (a) comparison of the samples and As₂O₃ and KBr standard simultaneously irradiated with slow neutrons; (b) the same as (a), but considering only bromine and using standards made by adding and homogenizing known amounts of KBr in the PVC latex. All measurements were based on γ-spectrometry. The mean values given by method (a) are: arsenic (2.5±0.4)·10⁻⁴%, bromine (1.9±0.1)·10⁻³%. In method (b) the bromine found was (2.47±0.03)·10⁻³%.     

Non-destructive analysis of inorganic impurities in Brazilian coals by epithermal neutron activation

Twenty-two elements were identified and determined in different Brazilian coal samples by an epithermal neutron activation technique developed by the authors. The detection limits and the uncertainties of the results show that the technique can be used for routine analysis. The analysis of the complex gamma-ray spectra and the evaluation of the interfering activities are discussed in detail.     

Determination of trace impurities in palladium by neutron activation analysis

Trace amounts of Ir, Au, Ag, Pt, Zn, Mn, and Cu were determined in high purity palladium by destructive and instrumental neutron activation analysis (NAA). The latter version of NAA was employed for the determination of Ir, Au and Ag. Special attention was paid to a new non-destructive method for the determination of silver traces in palladium. The results obtained by both versions of NAA are critically discussed and compared.     

Determination of trace impurities in tin by neutron activation analysis

Two methods are described to determine indium and managenese in high-purity tin. In the first method indium and manganese are separated from the tin and antimony matrix activities on Dowex 1X8 anion exchanger. Tin and antimony are adsorbed in 10M HF while indium and manganese are eluted. In the second method the incident γ-ray intensity due to the tin matrix is reduced by placing a lead absorber between the sample and the detector. The reproducibility and the sensitivity of both methods are of the order of 10 ppb for manganese and of 1 ppb for indium for 1 g samples and a neutron flux of 10¹¹ n·cm⁻²·sec⁻¹. Aspirant of the N. F. W. O.     

Determination of trace impurities in tin by neutron activation analysis

Arsenic, selenium and antimony were determined in four different tin samples. After distillation from HBr?H₂SO₄ medium arsenic and selenium were precipitated with thioacetamide, and antimony was subsequently separated by deposition on iron powder. The separated samples were counted on a high-resolution Ge(Li) γ-spectrometer. The sensitivity of the method is highly satisfactory.     

Determination of trace impurities in tin by neutron activation analysis

A method was developed for the determination of 15 trace elements in tin. High-purity tin samples (99.9999% and 99.999%) as well as tin of technical quality were analysed. Reactor neutron activation of the tin samples was followed by distillation of the matrix activities from a HBr−H₂SO₄ medium and Ge(Li) gamma-ray spectrometry of the distillation residue. The sensitivity of the method is generally high. For the high-purity samples the detection limits vary from 0.02 ppb (scandium) to 200 ppb (iron) for irradiation of 1 g of tin for 1 week at a thermal flux of 5·10¹²n·cm⁻². ·sec⁻¹. To decontaminate the surface of the tin samples, pre- and post-irradiation etching procedures were applied. The efficiency of these etching techniques was studied.     

Determination of trace impurities in platinum by neutron activation analysis

Determination of trace impurities in platinum by neutron activation analysis was carried ont by combining the advantages of ion exchange chromatography and Ge(Li spectrometry. Owing to the development of a new ion exchange separation scheme which assures high decontamination factors with respect to matrix activities and practically quantitative yields, ppm and sub ppm amounts of Au, Cu, Ir, K, La, Mn, Pd and Zn were determined in 10 mg samples of pure platinum metal. No determinations of the chemical yield were necessary. Several other elements could be determined, if present, without essentially changing the procedure.     

Determination of impurities in high-purity solvents by neutron activation analysis

The determination of impurities in high-purity solvents, (acetone, isopropanol, trichloroethylene and trichlorotrifluoroethane) used in the production of integrated circuits was carried out by reactor neutron activation analysis. A special vacuum evaporation technique was used for the preconcentration of the solvents. The results showed that sodium and iron are the main impurity components in the solvents and on the other hand the quality of the solvents satisfies the specifications required by high-technology standards. The suspended solid particles in solvents were counted by a Microscopic Image Analysis System (MIAS).     

Determination of certain trace impurities in uranium concentrates by activation analysis

A method is presented for the simultaneous determination of chromium, iron, cobalt and zinc in samples of uranium concentrates, oxides and metallic uranium by neutron-activation analysis. The method involves adequate decontamination of gross fission product activities by adsorption on silica gel, removal of uranium by solvent extraction, separation of most carrier-free rare-earth activities by coprecipitation with aluminium chloride, and, finally, fractional separation of the elements concerned by ion-exchange chromatography. The method can assay ppm of such elements in limited quantities of samples by scintillation gamma-ray spectrometric analysis with a reproducibility of 10-15%.     

Determination of impurities in tantalum by a radiochemical neutron activation analysis

A radiochemical separation method using Dowex 1×8 (200–400 mesh) has been applied to two tantalum metals of 99.9% purity. While tantalum was still retained on the resin, the elements Na, K, Cr, Mn, Fe, Co and Zn were separated with 2M HF and subsequently the elements Sc, As, Zr, Mo, Eu, W and Hf with a mixture of 0.5M HF and 3M HCl. The separation yields for all impurities was 98–100%. Elemental contents were calculated by a single comparator method using two monitors.     

Determination of impurities in zircaloy clad by means of neutron activation analysis

A method is described for determining impurities in Zr-2 and Zr-4 clads by means of instrumental neutron activation analysis followed by high resolution gamma-ray spectrometry. The samples were irradiated in IRT-5000 using vertical channels and a pneumatic system with neutron fluxes of about 3·10¹³ and 4.8·10¹¹ n·cm^–2·s^–1, respectively, and counted using Ge(Li) detectors coupled to an on-line computer. The following impurties have been determined Al, Cr, Mn, Fe, Co, Ni, As, Sn, Sb, Hf and W.     

Determination of impurities in nuclear fuel element components by neutron activation analysis

Neutron activation analysis methods for the determination of impurities in zirconium cladding material and uranium oxide are described. Detection limits for the elements Al, Cd, Cr, Co, Cu, Hf, Fe, Mn, Ni, W and U in zirconium are below that required by the ASTM B 352-79 standard. The method has been tested on the NIST SRM 360a Zircaloy-2 from which the elements Na, Mg, Al, Ca, V, Cr, Fe, Co, Ni, Cu, Eu and U have been detected. The values for Cr, Fe, Ni and Cu are compared with the certified values. A method for the pre-irradiation separation of the elements Mg, Na, Al, K, Sc, Ca, V, Mn, Cr, Fe, Co, Cu, Zn, Rb, Zr, Cd, Cs, REE and Hf from uranium has been developed. A neutron activation analysis method for the determination of those elements in uranium is described. The method is tested by the analysis of the IAEA reference sample SR-54/64. The elements Al, Mn, V, Cu, Cr, Co, Ni and Fe have been detected and the results compared with the certified values.     

Determination of trace element impurities in aspirin tablets by neutron activation analysis

Twenty five trace and minor elements (aluminium, arsenic, barium, bromine, cerium, chlorine, cobalt, chromium, cesium, europium, iron, hafnium, potassium, magnesium, manganese, sodium, rubidium, antimony, scandium, selenium, strontium, thorium, titanium, vanadium and zinc) in five different Egyptian aspirin brands (Aspo, Askin, Aspocid, Aspeol and Rivo) have been determined by instrumental neutron activation analysis. It has been concluded that the concentration of arsenic, barium, bromine, cobalt, chromium, iron (except in Aspocid), magnesium, manganese, rubidium, selenium, strontium and zinc in the Egyptian brands is below or within the concentration range reported for these elements in 16 American aspirin and aspirin-like brands.     

Determination of impurities in niobium metal by a radiochemical neutron activation analysis

A radiochemical separation method using an anion exchange resin has been applied to 3N grade Nb for determining nine impurity elements. Five elements (Cr, Fe, Co, Zn and Se) were separated in 2M HF, three elements (Mo, W and Hf) in 32M HF, Nb in 0.5M HF/3M HCl, and Ta in 1M NH₄F/4M NH₄CCl. The contents of the elements were calculated by a single comparator method using two monitors of Au and Co. The main impurity was revealed to be Ta with a content of over 160 ppm.     

Determination of impurities in semiconductor grade silicon by instrumental neutron activation analysis

Instrumental neutron activation analysis has been applied to semiconductor grade silicon to study the concentration levels of impurity elements, the contamination during the single crystal growing process, and the vertical and radial distributions of impurities, along with the decontamination effect in the analysis. Twenty elements of Au, Br, As, W, Cr, Co, Na, Eu, La, Se, Zn, U, Th, Hf, Fe, Sb, Ag, Ce, Tb and Ta have been analyzed in p- and n-type wafers, single crystals and a polycrystal by a single comparator method using two comparators of gold and cobalt. Considerable surface contamination has been found and could be removed by etching the surface with nitric and hydrofluoric acid before and after irradiation. The impurity concentration has been found to be generally increased in the process of single crystal growth. The vertical and radial distributions of impurities have revealed that some impurity elements were more concentrated in the top region of a single crystal rod than in the middle region, and that Br, Cr, La, Eu and Sb were enriched in the central region and As, U and Fe in the outer region.     

Determination of impurities in ice-cores form the Jungfrau-Joch by neutron activation analysis

An ice-core of 4 m length was drilled at the Jungfraujoch. It was divided into 18 sections and analyzed for solid and dissolved material by neutron activation analysis using nondestructive counting as well as chemical group separations. The solid material was identified as stone dust. Part of the dissolved material seems to originate from dissolved limestone, whereas many elements can not be accounted for by this hypothesis and must be due to atmospheric fallout.     

Determination of Ta impurities in Nb samples by X-rays in neutron activation analysis

Ta impurities in Nb samples have been determined by X-rays in 14 MeV neutron activation analysis. For X-ray detection, (HP) Ge detector with Be-window is used. The sensitivity of the determination has been found to be about 30 g (in Nb).This work was supported by the National Foundation for Research (Contract No. 259).     

Determination of impurities in marbles from different deposits in Yugoslavia by activation analysis

Impurities in marbles from the deposits in Petrovac na Mlavi, near Gostivar (Duf and Sušički Most) and Venčac in Yugoslavia have been determined by activation analysis. The impurities of Na, Mn and Cu were determined from the characteristic photopeaks with γ-energies of 1.38 and 2.78 MeV (²⁴Na); 0.511 MeV (⁶⁴Cu) and 0.850 MeV (⁵⁶Mn), and from the corresponding half-lives of these radioisotopes. The concentrations of Mn, Na and Cu were also determined in every marble sample.     

Determination of impurities in single crystals of magnesium oxide by neutron activation analysis

The determination of some trace impurities in single-crystal magnesium oxide is described. Radiochemical separations of iron, cobalt, scandium, manganese and chromium by ion exchange and solvent extraction are applied in conjunction with γ-spectrometry. The impurities that give rise to long-lived γ-emitting isotopes are considered.     

Determination of impurities in titanium and titanium oxide by radiochemical neutron activation analysis

A radiochemical neutron activation analysis has been applied to 2N–4N grade titanium metal and its oxide. Twenty two impurities were separated in a group from scandium by a radiochemical separation method using cation exchange resin with HBr and HCl. The contents of the elements were calculated by a single comparator method using two monitors. The analytical results agree well within 10% deviation with those obtained by instrumental method. Eighteen elements, Na, Fe, Co, As, Se, Sr, Mo, Sb, La, Eu, Tb, Yb, Lu, Hf, Ta, W, Th and U, are determined in titanium oxides and 17 elements, Na, Cr, Fe, Co, Se, As, Zr, Mo, Sb, Cs, Ce, Tb, Yb, Hf, Ta, W and Th, in titanium metals.