Determination of total iron in standard rocks by spectrophotometric titration with EDTA

A method for the determination of total iron in silicate rocks is described. It is based on spectrophotometric titration of iron(III) with EDTA after decomposition in a PTFE bomb. No prior separation of interfering elements is needed. The method was tested by analysis of the U.S. Geological Survey reference rocks G-2, AGV-1, GSP-1, BCR-1 and PCC-1. The same sample solutions were also analysed by atomic-absorption spectrophotometry. The agreement with published and recommended values was good.     

Instrumental neutron activation analysis of Moroccan geological samples using the k0-standardization method

Instrumental neutron activation analysis (INAA) for traces and major elements of several geological samples from “Zgounder” region in Morocco was performed utilizing the k ₀-standardization method. Sample irradiation has been done by the 250 kW Triga Mark II reactor at Jozef Stefan Institute in Slovenia. Due to its accuracy, sensitivity and specificity, the k ₀-standardization method is the most suitable method for non-destructive multielement analysis mainly for trace elements in rocks. It requires an accurate knowledge of the parameters of the irradiation facilities and other instrumentation parameters. It is an absolute standardization method, where the absolute nuclear data are replaced by a nuclear constant, the k ₀-factor, determined experimentally with high accuracy. More than 40 elements were determined using about 30-second short and about 7-hour long irradiations. Gamma-rays emitted from the irradiated samples have been determined by a high purity germanium detector. Accuracy was assessed using the standard reference material AGV-1. This was less than 1% for major elements and about 5% for traces. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of carrier yields for neutron activation analysis using energy dispersive X-ray spectrometry

A new method is described for determining carrier yield in the radiochemical neutron activation analysis of rare-earth elements in silicate rocks by group separation. The method involves the determination of the rare-earth elements present in the carrier by means of energy-dispersive X-ray fluorescence analysis, eliminating the need to re-irradiate samples in a nuclear reactor after the gamma ray analysis is complete. Results from the analysis of USGS standards AGV-1 and BCR-1 compare favorably with those obtained using the conventional method.     

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.     

Analysis of low levels of rare earths by radiochemical neutron activation analysis

A procedure for the radiochemical neutron-activation analysis for the rare earth elements (REE) involves the separation of the REE as a group by rapid ion-exchange methods and determination of yields by reactivation or by energy dispersive X-ray fluorescence (EDXRF) spectrometry. The U. S. Geological Survey (USGS) standard rocks, BCR-1 and AGV-1, were analyzed to determine the precision and accuracy of the method. We found that the precision was ±5–10% on the basis of replicate analysis and that, in general the accuracy was within ±5% of accepted values for most REE. Data for USGS standard rocks BIR-1 (Icelandic basalt) and DNC-1 (North Carolina diabase) are also presented.     

An interlaboratory study of potassium determination in rocks and minerals

Seven laboratories took part in this interlaboratory study which was part of an investigation of the flame-speetrometric determination of potassium in rocks and minerals suitable for potassium-argon age-measurement. Three of these laboratories determined potassium in the following five international reference rocks: tonalite T-1, basalt BCR-1, andesite AGV-1, granite G-2, and granodiorite GSP-1. The other five samples (with the number of laboratories analysing them in parentheses) were: a chlorite rock (7), an altered basic igneous rock (5), an altered basaltic andesite (5), a biotite (6) and a potassium feldspar (7). Details of sample preparation and methods of analysis are given; no laboratory used exactly the same method as any of the other six laboratories. Results have been examined by analysis of variance; larger relative between- and within-laboratory variations occurred for the two samples containing less than 0.1% potassium than for seven of the eight other (higher potassium) samples; between-laboratory variations for the basalt BCR-1 and, to a lesser extent, the andesite AGV-1, were high and of similar magnitude to those for the samples containing less than 0.1% potassium. The causes of any poor interlaboratory agreement in the present study are considered.     

Instrumental neutron activation analysis based on k0-standardization method as compared with other methods in the analysis of the IAEA inter-comparison test

Results of inter-comparison test organized by the IAEA are analyzed according to the contribution and performance of INAA as non-destructive method for trace elements analysis as compared to other techniques. Several methods were employed for certifying the biological sample (IAEA-0140) and were also compared. It is shown that NAA is the method of a good accuracy and precision. The biological sample has been investigated by INAA based on semi-absolute technique. More than 30 elements have determined without using standards. The reference materials, which are certified in this manner and utilized as primary standard, are also discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Application of an Apple IIe microprocessor for data acquisition and analysis in instrumental neutron activation analysis with a low energy photon detector

The determination of thirteen elements, eleven rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Tb and Lu), thorium and uranium were performed by instrumental neutron activation analysis for four geological reference materials (G-2, AGV-1, GSP-1 and SY-2) as well as our laboratory rare-earth standard. The analyses were performed using a low energy photon detector coupled to an Apple IIe microprocessor employed as a multichannel analyzer not only to collect the data but also for data analysis. Finally, based on this work we have proposed a simple, rapid routine method for the determination of eleven rare-earth elements, thorium and uranium in geological materials employing IVIC's RV-1 nuclear reactor.     

Mössbauer Study of El-Bahrain Meteorite

Procedures for the determination of traces of rare earth elements (REE) in geological samples by instrumental neutron activation analysis (INAA) and high resolution liquid chromatography (HPLC) are presented. The international standard reference materials AGV-1, GSP-1 and G-2 (USGS) were tested for the determination of REE concentrations using both techniques. The results obtained showed good agreement with certified values, giving relative errors less than 10%. By using INAA, the REE La, Ce, Nd, Sm, Eu, Tb, Yb and Lu were determined. All the REE, except Dy and Y, were determined when HPLC was employed. The application of INAA and HPLC to the determination of REE in geological samples is also discussed.     

Determination of trace elements in iron by neutron-activation techniques

A systematic analytical procedure for the determination of some trace impurities in iron matrices was developed by employing both direct and destructive neutron-activation techniques. Irradiations in fast neutron fluxes, selective activation by epithermal neutrons and coincidence γ-spectrometry measurements were used in some cases, in order to improve the sensitivity for non-destructive analysis; for destructive methods, radiochemical separations based on ion exchange and solvent extraction were applied. Procedures are described, and some results of the determination of low concentrations of Al, Mn, Ti, V (non-destructive), P, S, Zn (destructive) and As, Co, Cr, Cu, Mo, Ni, Sc, W (both methods) in iron are reported and discussed.     

Determination of rhodium by thermal neutron activation analysis using g-ray spectrometry

Trace amounts of rhodium have been determined by thermal neutron activation analysis using both destructive and non-destructive methods. With a neutron flux of 10¹² n cm^-2 sec^-1 the lower limits of detection are about 0.1 μg and 0.01 μg, respectively. A rapid sodium-peroxide fusion followed by a pyridine extraction was used in the destructive method to separate the 4.4-mm ^104mRh from its matrix. The 44-sec¹⁰⁴Rh was used in the non-destructive method. Both radioactive isomers were measured by γ-ray spectrometry with a multichannel pulse height analyzer. The average time required per non-destructive analysis was 7 min while the chemical method averaged 20 min.     

碱熔-标准物质法-电感耦合等离子体发射光谱(ICP-AES)法测定硅酸盐岩中10种主量元素

硅酸盐岩元素的准确测定是其地球化学分析研究的基础,其主量元素含量通常可以采用电感耦合等离子体发射光谱(ICP-AES)法测定,但其测定方法的系统性研究相对缺乏,尤其是样品前处理和基体干扰的有效消除两方面。前处理过程中,考察不同熔剂用量对硅酸盐岩样品的分解能力,发现当熔剂与样品比例达到6:1后,熔珠为纯色透明,经稀硝酸提取后溶液澄清,确定了硅酸盐岩前处理时熔剂与样品的最佳配比。测定过程中,通过考察基体匹配法和标准物质法两种基体干扰消除方法对测定结果的影响,发现当采用与岩性一致或者接近的标准物质绘制校准工作曲线时,基体干扰消除效果更好,更适用于测定硅酸盐岩10种主量元素含量。据此,建立了硅酸盐岩经偏硼酸锂熔融,稀硝酸振荡提取处理,以标准物质法绘制校准工作曲线,采用ICP-AES法同时测定SiO2、Fe2O3、Al2O3、CaO、K2O、MgO、Na2O、TiO2、P2O5、MnO 10种成分含量的方法。对岩石标准物质GBW07107进行分析测定,方法的相对标准偏差(RSD)为0.17%～0.75%,方法检出限为0.001%~0.016%,满足硅酸盐岩样品元素定量分析的要求,而且操作简单快速,环境污染小,适用于大批量样品分析。     

Activation analysis for selenium and tellurium trace impurities in gallium, arsenic and gallium arsenide

Destructive and non-destructive activation analysis for selenium and tellurium has been studied. In destructive analysis the selenium and tellurium activities are co-extracted from the irradiated and dissolved matrix elements with dithizone/CCl(4), reagent in a hot-chamber by remote manipulation, then separated from each other by diethylammonium-N,N-diethyldithiocarbamate/CCl(4) extraction, tellurium going into the organic phase and selenium being retained by the aqueous phase. The sensitivity of the method is 10(-8)g for both elements. By non-destructive methods, selenium can be determined down to 10(-6)g on short irradiation, and down to 3 x 10(-8) g on long irradiation and cooling, and tellurium down to 10(-6) g with long irradiation and cooling.     

Advances in Radiogeochemistry

The applications of reactor thermal and epithermal neutron activation analysis (NAA) to geological materials are reviewed. These include the historical development of radiochemical (destructive) (RNAA) and instrumental (non-destructive) (INAA) methods, the counting systems, epithermal neutron activation. Special attention is given to reference materials and the place of NAA in the firmament of geoanalytical techniques for their certification and characterization. Literature references useful in NAA of geological materials are listed.     

Interferences of oxide, hydroxide and chloride analyte species in the determination of rare earth elements in geological samples by inductively coupled plasma-mass spectrometry

The analytical procedure for the determination of Ba and rare earth elements in rocks and minerals by ICP-MS is described. The yield of mono-oxide and hydroxide ions of Ba and rare earth elements, and chloride ions of Ba has been determined. A Microsoft Excel spreadsheet template has been written to calculate the expected peak intensities for all possible analyte species (M⁺, MO⁺, MOH⁺ and MCl⁺) as a function of the mass number. The degree of interferences of different analyte isotopes is estimated and interferent equivalent concentrations are given for elements, for which no isotope free from interferences is available. The method is applied to the analysis of the four Geo-Reference samples AC-E, GSP-1, G-2 and AGV-1; the analytical accuracy is better than ±10% for most of the elements when compared with recommended reference values.     

Instrumental neutron and photon activation analyses of selected geochemical reference materials

Ten selected rock reference materials (USGS diabase W-1, basalt BCR-1, andesite AGV-1, granite G-2, granodiorite GSP-1, and CRPG basalt BE-N, granite GS-N, trachyte ISH-G, serpentine UB-N, glass standard VS-N) were analyzed by instrumental neutron and photon activation analyses. The results have been evaluated on average for the entire set of samples to detect possible systematic deviations of the determined values from the reference values. Out of 47 elements determined, 43 elements have been determined with reasonable agreement (deviation < 10% on average) with the reference values. Au could not be determined because of a high blank from packaging polyethylene foil. Systematically higher Dy and lower Ho and Tm (by about 20% on average) in the present results require further investigation. In several cases, reasons for greater differences between the determined and recommended values could not be traced in the procedures used within the study. The most suspect is the recommended value for W in the CRPG BE-N basalt, which is twenty-five times higher than the present value, probably due to inconsistent contamination from a W carbide mill used in production of this reference material.     

Evaluation of a quantitative method for trace impurities in arsenous acids by synchrotron radiation X-ray fluorescence spectrometry and inductively coupled plasma-atomic emission spectrometry.

Thirteen arsenous acid samples of known origins and refining methods were collected. Each sample was subjected to quantitative analysis of any impurity elements present using synchrotron radiation X-ray fluorescence spectrometry (SR-XRF) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). The trace elements selected were Sn, Sb and Bi for the reasons that they were considered not to be changed by their circumstances and that they showed high sensitivity to SR-XRF. These results obtained by both methods were compared and the correlation between these two methods was determined. The quantification of trace impurities obtained by SR-XRF using As as an internal standard showed good agreement with the results obtained by ICP-AES. The discrimination of refining method became possible by the comparison of these impurities' contents measured with non-destructive SR-XRF using several arsenous acid particles.     

Elemental characterization of the new Czech meteorite ‘Morávka’ by neutron and photon activation analysis

Forty two major, minor and some trace elements were determined by activation analysis in the new Czech Morávka H5 chondrite, which fell on May 6, 2000 in the vicinity of Morávka, north-east Moravia. The elements Na, Mg, Al, Si, Cl, Ca, Ti, V, Mn, Co, Ni, and Cu were determined by means of instrumental short-time neutron activation analysis (INAA), whereas another group of elements, namely Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Sb, La, Sm, Ir, Au and Hg were assayed using long-time INAA. Most of the rare earth elements (REE) were determined by radiochemical neutron activation analysis (RNAA) using precipitation of their oxalates, whilst for the determination of Rb and Cs an RNAA procedure based on selective sorption of the elements on ammonium phosphomolybdenate was employed. Mg, Ca, Ti, Mn, Ni, Sr, Y and Zr were determined by instrumental photon neutron activation analysis (IPAA) using the irradiation with 20 MeV bremsstrahlung from a microtron. For quality control, the U.S. Geological Survey (USGS) reference rocks basalt BCR-1 and diabase W-1 were analyzed. Moreover, the self-verification principle in activation analysis was employed to increase the credibility of the obtained results.     

The correction of interference effects in the determination of the rare earth elements and hafnium by spark-source mass spectrometry

Superpositional interferences from oxide ion species cause significant errors in the spark-source mass spectrometric determination of hafnium and the rare earth elements when aluminium is used as the conducting matrix for samples such as rocks and soils. A mathematical correction procedure is described in which corrections are made in any particular exposure by using intensity measurements derived from that exposure alone. Its effectiveness is demonstrated for the USGS Standard Rocks BCR-1, AGV-1 and G-2.     

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.