Multi-element determination in silicate rocks by instrumental neutron activation analysis

Instrumental neutron activation analysis technique was applied for the determination of 20 elements in 54 silicate rock samples which belong to three sedimentary geological formations located in the western desert of Iraq. The samples along with USGS standards were irradiated in an IRT-5000 reactor at a neutron flux of 3.7·10¹³ n·cm^–2·s^–1 The following minor and trace element constituents have been determined: Na, K, Ca, Fe, Sc, Cr, Co, Zr, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, Th and U.     

Determination of indium in standard rocks by neutron activation analysis

A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained.     

Determination of sodium and chlorine in pure water by neutron activation analysis

Neutron activation analysis was applied to determine sodium and chlorine in high purity water samples. After irradiation of the sample,³⁸Cl was purified from⁸²Br and other nuclides by carbon tetrachloride extraction and silver chloride precipitation, and²⁴Na was separated from other alkali elements and other nuclides by adsorption of²⁴Na on HAP. The activities of both elements were measured by conventional G.M. counter. The contamination of the elements from container walls during neutron irradiation and the interference with³⁸Ar(n, p)³⁸Cl reaction on argon dissolved in water were also examined. Water samples containing 3 ppb of chlorine could not be determined accurately, owing to the above mentioned interfering reaction.     

Interference from uranium in neutron activation analysis or rare-earths in silicate rocks

A direct nondestructive method of analysis for²⁴¹Am utilizing photon counting and self-absorption correction factors is presented. The method gives favorable agreement for samples analyzed by radiochemical separation procedures and alpha particle spectrometry. The comparison was made over a range of approximately five orders of magnitude of²⁴¹Am concentrations. The method is reliable and relatively simple. Sensitivity for a ∼5-g sample and a counting intervals of 60 000 s is ∼0.2 pCi/g with an uncertainty of ±22%, which decreases to ±11% for increased counting intervals of 150 000 s and an increased sample size of ∼20 g.     

Determination of rare earths in silicate rocks by epithermal neutron activation and a simple group separation

The determination of nine rare earth elements in rock samples by epithermal neutron activation, followed by a simple group-separation procedure and Ge(Li) γ-ray spectrometry, is described. This method is found to be advantageous for the determination of Nd, Gd, Ho, Er and Lu by means of the short-lived nuclides¹⁴⁹Nd,¹⁵⁹Gd,¹⁶⁶Ho,¹⁷¹Er and^176m Lu. Precision for La, Sm and Eu is similar to that of thermal neutron activation, that for Dy is worse. Samples of the standard rocks, basalt BCR-1 and granite G-2, were analyzed by this procedure and the results obtained are compared with previously reported data.     

Routine multielement instrumental neutron activation analysis of silicate rocks using short-lived radionuclides

By means of thermal neutron activation and countings on the small planar and large coaxial Ge(Li) detector, 13 elements are determined in various silicate rocks, using short-lived radionuclides with half-lives from 2 min to 15 h. A method of routine analysis with simple dead-time and pile-up correction is described and tested with the standard rocks AGV-1 and G-2.     

Gamma-ray photopeak interferences found in the instrumental neutron activation analysis of silicate rocks

Data are tabulated to identify all major and minor gamma-ray interferences which may effect the area determinations of analytical photopeaks for all principle isotopes (of half life greater than about one day) encountered during the routine instrumental neutron activation analysis of silicate rocks. These photopeaks cover the energy range 60–1700 keV and are based on data abstracted from ERDTMANN and SOYKA.⁸ Interferences are listed down to relative intensities of 0.001% and include principle sum peaks. Photopeaks which are considered to be most reliable for routine quantitative analysis are identified.     

Determination of chlorine distribution in silicon dioxide by neutron activation

A neutron activation method for the determination of chlorine distribution in silicon dioxide on the surface of Si wafers has been developed. After irradiation of the sample with a standard, successive layers are removed from the oxide surface by chemical etching and the chlorine content in the solutions obtained is determined gamma-spectrometrically. Using a Ge(Li) detector, a lower limit of determination of 1.0·10⁻⁷ g was obtained. This limit can be improved by using a NaI(Tl) detector. The error of chlorine determination is discussed.     

A well-tested procedure for instrumental neutron activation analysis of silicate rocks and minerals

Procedures for instrumental neutron activation analysis (INAA) have been developed and used on more than a thousand small samples of terrestrial and lunar silicate rocks and minerals for determination of Co, Cr, Fe, Hf, Na, Ni, Sc, Ta, Th, and the rare earths La, Ce, Sm, Eu, Tb, Yb, and Lu. Precision has been determined by repeated analysis of Knippa basalt and DTS-1 to be better than ±5 percent for all elements except Ni, Yb, Lu, and Hf. Mean values and estimates of accuracy are given for Knippa basalt and USGS standards AGV-1, G-2, GSP-1, and W-1. Important features of the method are its precision and ease of data reduction.     

Rare earth element determination in silicate rocks using neutron activation analysis and mass spectrometry

A pre-irradiation group separation procedure for the quantification of 11 to 13 rare earth elements (REE) in geological materials by neutron activation analysis, with yield determination by mass spectrometry isotope dilution analysis of Sm and Nd, is described. Utilization of the shorterlived isotopes of the REE allow sufficient data for most geochemical studies to be obtained within one day of irradiation, although where necessary additional information may be obtained following a decay period of three to four weeks. Analysis of selected USGS rock standards shows the method to be both accurate and precise.     

Determination of nitrogen by neutron activation in meteorites and rocks

The results of determination of nitrogen content in meteorites by neutron activation are reported. The method is based on the¹⁴N(n,p)¹⁴C reaction, which occurs upon irradiation of the samples by neutrons. The use of proportional gas-filled countes for the recording of¹⁴C made it possible to obtain the low nitrogen detection limit of 0.001 g.     

Optimization of instrumental neutron activation analysis for studying the chemical composition of silicate rocks

Software for optimization of instrumental neutron activation analysis of geological samples, preferentially silicate rocks, and a technique for evaluation and minimization of interference of gamma-ray lines are given. The maximum relevant signal-to-noise ratio was taken as a criterion for optimization by taking into account information available from a large number of lines in the gamma spectra studied.     

Optimization of instrumental neutron activation analysis for studying the chemical composition of silicate rocks

Software for optimization of instrumental neutron activation analysis of geological samples, preferentially silicate rocks, and a technique for evaluation and minimization of interference of gamma-ray lines are given. The maximum relevant signal-to-noise ratio was taken as a criterion for optimization by taking into account information available from a large number of lines in the gamma spectra studied. Received: 17 July 1997 / Revised: 7 November 1997 / Accepted: 16 November 1997     

Determination of chlorine, bromine and iodine in rock samples by radiochemical neutron activation analysis

Chlorine, bromine and iodine (hereafter, halogens) were detemined for rock samples by radiochemical neutron activation analysis. The powdered samples and reference standards prepared from chemical reagents were simultaneously irradiated for 10 to 30 minutes with or without a cadmium filter in a TRIGA-II reactor at the Institute for Atomic Energy, Rikkyo University. The samples were subjected to radiochemical procedures of halogens immediately after the irradiation. Iodine was firstly precipitated as PdI₂, and chlorine and bromine were successively precipitated as Ag-halides at the same time. In this study, geological standard rocks, sedimentary rocks and meteorites were analyzed for trace halogens. In some Antarctic meteorites, iodine contents were observed to be anomalously high. Chlorine contents also are somewhat high. The overabundance of iodine and chlorine must be caused by terrestrial contamination on the Antarctica.     

Group separation of rare earth elements by liquid-liquid extraction for the neutron activation analysis of silicate rocks

Rare earth elements are isolated as a group from neutron activated rock samples by a new radiochemical procedure based on extraction with thenoyltrifluoracetone/phenanthroline in CHCl₃. The procedure consists of three extraction steps, obviates the use of anactive carriers and gives practically quantitative chemical yields, thereby avoiding fractionation of the individual rare earths. Details of the dissolution, chemical separations and counting procedure are given togther with an analysis of BCR-1.     

Interference in neutron activation analysis of rocks by uranium fission

Interferences by uranium fission for⁹⁵Zr,⁹⁹Mo,¹⁰³Ru,¹⁴⁰La,¹⁴¹Ce and¹⁴⁷Nd have been studied using a single comparator method with two monitors. The effect of the neutron energy spectrum on the interference factor was examined by using the effective activation cross section. All the activities of¹⁴⁰La produced during neutron irradiation of uranium were included in the calculation of the factor for lanthanum. The calculated and experimental interference factors are in good agreement within 10% deviation. The results have been applied for the analysis of several rock samples containing uranium in a wide concentration range.     

Precision analyses of manganese in rocks by neutron activation analysis

A simple and rapid procedure for the determination of manganese in rocks by neutron activation and γ-spectrometry is presented. The precision of the method calculated from analyses of standard rocks is of the order 1.5–2%, and an accuracy of ±2% is attainable. The method is applicable to most types of geological samples, and should be superior to conventional methods used in rock analysis.     

The determination of bromine in rocks by neutron activation analysis

A neutron activation method for the determination of bromine in rocks and minerals is described. After removal of iodine, bromine is separated by oxidation with potassium permanganate and extraction with carbon tetrachloride. Bromine is thon precipitated as silver bromide; yields are from 60 to 84%. The method has a sensitivity of 0.001 p.p.m. of bromine and is free from interfering reactions. The values obtained for G-1 and W-1, 0.484 and 0.490 p.p.m. of bromine respectively, are lower than the average values for granites and basalts previously reported.     

Determination of 32 elements in rocks by neutron activation analysis and high resolution gamma-ray spectroscopy

Neutron activation analysis and Ge(Li) spectroscopy was used to determine 32 elements in seven U.S.G.S. standard rocks of a wide range of composition. Short half-life nuclides (10 sec-10 min) were used to measure Sc, Hf, Dy, Mg, Al, Ca, Ti, V (and Na) in an automated rabbit Ge(Li) detector system. The elements K, Cu, Zn, Ga, Sr, Ba, La, Eu, Sm (and Mn) were determined by dissolution of the irradiated sample followed by removal of²⁴Na on hydrated antimony pentoxide (HAP). Long-lived nuclides were used to measure Sc, Cr, Fe, Co, Zr, Rb, Sb, Cs, Ba, Ce, Eu, Yb, Tb, Lu, Hf, Ta and Th after decay of²⁴Na. The method involves little radiochemistry and the separation is selective for²⁴Na under the experimental conditions used. Elemental concentrations determined agree well with previously published data.     

Determination of gold by neutron activation analysis in some selected precambrian rocks from Eastern India

Gold was determined in some selected rock samples by neutron activation analysis. The analysis was carried out both in destructive and non-destructive ways followed by γ-ray spectrometry. The amounts of gold that were determined in the respective rock samples varied in the range 10⁻⁴–10⁻⁶%. Besides gold, some other trace constituents such as As, Ag, Sb, W, Se, La, Sm, etc. were also detected and their approximate order of occurrence was determined.