Comparative study of activation analyses for the determination of trace halogens in geological and cosmochemical samples.

Halogens (fluorine, chlorine, bromine and iodine) were determined by activation analyses (neutron activation analysis (NAA), photon activation analysis (PAA) and prompt gamma-ray analysis (PGA)) for geological and cosmochemical solid samples. We studied how each analytical method was for the determination of trace amounts of halogens in rock samples. Radiochemical NAA (RNAA) showed the highest analytical reliability for three halogens (chlorine, bromine and iodine), whereas a set of four halogens (fluorine, chlorine, bromine and iodine) could be determined in principle by radiochemical PAA (RPAA) from a single specimen. Although it is a non-destructive method, PGA showed an analytical sensitivity for chlorine comparable to those of RNAA and RPAA.     

Instrumental neutron activation analysis of geochemical and cosmochemical samples: A fast and reliable method for small sample analysis

We have developed a fast and reliable procedure to routinely measure the abundances of up to about 35 elements even in small (<1 mg) samples. Depending on the type of samples, they are either irradiated for about 8 hours at a flux of about 2·10¹²n·cm^–2·s^–1, or up to 100 hours at a flux of about 6·10¹³n·cm^–2·s^–1. As standards, high-purity synthetic multielement standards and well-characterized geological reference materials are used. Synthetic standards are used as primary standards because they have several advantages over secondary (geological) standards. Three to four counts are done one each sample, starting 1–3 days after the end of the irradiation. We use high-purity germanium (HpGe) detectors with high efficiencies and very good energy resolution (1.6–1.8 keV at 1332 keV). To allow high throughput rates we use fast preamplifiers and gated integrator spectroscopy amplifiers with fast fixed conversion time ADCs. The signals are fed into an acquisition interface module (AIM) and via Ethernet into a Micro VAX. To allow better peak deconvolution, 8k spectra are taken where possible. A specially designed annular NaI(TI) guard detector allows Compton suppression spectrometry. The system uses standard software and was tested with sets of geological standards and has given reliable results for a wide variety of samples, e.g., cosmic spherules in the 30–200 g weight range.     

Radiochemical neutron activation analysis of trace lanthanoids in geological and cosmochemical samples

In order to determine trace lanthanoids in geological and cosmochemical samples, an analytical procedure for radiochemical neutron activation analysis (RNAA) was developed, where lanthanoids are radio-chemically purified through precipitations of hydroxides and fluorides, and cation exchange using HBr as an eluent. Chemical yields are determined by reactivation. The procedure was applied to the Allende meteorite and geological standard rocks. Our data for Allende are in excellent agreement with literature values, and those values for standard rocks, JP-1 (peridotite) and JF-2 (feldspar), in which lanthanoids are depleted by orders of 1 to 2 compared with those in Allende, seem to be reasonable, although not properly evaluated because of large scatterings in their literature data. This suggests that the present RNAA procedure is highly effective in determining trace lanthanoids (less than 1 ng) in rock samples.     

Quantitative multielement analysis of geochemical and cosmochemical samples using spark source mass spectrometry

Summary Spark source mass spectrometry is a useful method for the chemical analysis of geochemical and cosmochemical samples. The technique is highly sensitive (limit of detection between 0.001 ppm and 0.1 ppm) and allows the simultaneous determination of about 70 major, minor and trace elements. With the help of electrical ion detection and multielement isotope dilution on solid and dissolved samples, a precision of better than ±5 % is obtained for many elements. The measured concentrations are in good agreement with literature data.

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Quantitative Multielementanalyse von geo- und kosmochemischen Proben unter Verwendung der Funken-Massenspektrometrie

Zusammenfassung Die Funken-Massenspektrometrie ist eine nützliche Methode für die chemische Analyse von geochemischen und kosmochemischen Proben. Diese Technik ist sehr empfindlich (die Nachweisgrenze liegt zwischen 0,001 ppm und 0,1 ppm) und ermöglicht die gleichzeitige Bestimmung von ungefähr 70 Haupt-, Neben- und Spurenelementen. Mit Hilfe des elektrischen Ionennachweises und der Multielement-Isotopenverdünnungsmethode an festen und gelösten Proben wird eine Genauigkeit von besser als ±5% für viele Elemente erreicht. Die ermittelten Konzentrationen stimmen gut mit Literaturdaten überein.

     

Radiochemical neutron activation analysis of Mo and W in geochemical and cosmochemical samples with an emphasis on the correction of fission products

Radiochemical neutron activation analysis (RNAA) was applied to geochemical and cosmochemical samples to determine trace amounts of Mo and W. To determine the Mo concentration by NAA accurately, the contribution of the fission products of U should be corrected. For that reason, we developed a simple and effective method, where a contribution of fissiogenic ⁹⁹Mo was estimated by monitoring the ratio of uranium fission-product ⁹⁹Mo to ¹³³I. Mo concentrations corrected for fission with the W concentrations were consistent with the literature values, showing that ¹³³I was found to be an effective monitor for fission correction. Detection limits are estimated to be 10 ppb for Mo and W and 30 ppb for U under the present experimental conditions.     

Application of multiple prompt gamma-ray analysis (MPGA) to geochemical and cosmochemical samples

A prompt gamma-ray analysis system using multiple detection method (MPGA system) was constructed at the neutron guide hall of the JRR-3M reactor of the Japan Atomic Energy Agency. We applied MPGA method to geochemical and cosmochemical samples to evaluate its analytical performance on signal to noise (S/N) ratio, sensitivity, and detection limit. The S/N ratio measured by MPGA system was larger than that by normal prompt gamma ray activation analysis (PGAA) at JRR-3M. For some elements, the S/N ratio was improved more than ten times. Several elements that are not detected by PGAA were detected by MPGA. At the present time, concentrations of major elements and trace elements with high neutron capture cross section in geochemical and cosmochemical samples were determined accurately by the MPGA system installed at JRR-3M. It is expected that it will determine a lot of trace elements after appropriate adjustments and modifications.     

A comparison of N-type semi-planar and coaxial INAA detectors for 33 geochemical reference samples

While INAA is becoming a less popular analytical technique and it is a mature tool, there are still many improvement happening in the field. The effect of the new semi-planar detector is evaluated as compared to geological reference material and as its performance to the classical coaxial detector. The semi-planar detector offers improved accuracy (about 5%) for many analytes (As, Ba, Ce, Co, Cr, Eu, Hf, Lu, Nd, Rb, Sm, Th, U, Yb and Zn) while the coaxial gives an accuracy in the range of 10-15%.     

Semi-empirical determination of detector absolute efficiency in INAA of voluminous samples

When neutron activation analysis of voluminous samples is performed using the absolute method, the detector absolute efficiency for -ray emiting distributed sources must be known. In this study, a Monte-Carlo program was developed to include the calculation of the effective solid angle subtended by a collimated detector from irregularly shaped voluminous samples. The program cna cope with dififerent sample shapes and geometries provided that the sample covers the view of the detector. Data such as the source and detector dimensions, the source-detector distance, the detector view at a cartain distance, the thickness and the composition of any intervening materials, the -ray energies of interest and the corresponding attenuation coefficients for each material are required. The method adopted for calculating the detector absolute efficiency of the voluminous sample in a certain geometry takes into account the effect by -rays baing emited from different position within the sample and also considers their attenuation in the sample material as well as any intervening materials between the sample and the detector and is compared with a reference point source. The alculations are varified experimentally using a distributed source of 75 mm diameter and 100 mm thickness and two semiconductor detectors. The difference between the calculated and measured absolute efficiencies did not exceed 4%.     

Comparison study of RNAA and ICP-MS for the determination of ultra-traces of Th and U in geological and cosmochemical samples

In order to determine thorium and uranium traces in geochemical and cosmochemical samples, we developed an ICP-MS procedure, in which an anion-exchange step was introduced after sample digestion to separate major matrix elements, leading to decrease the dilution factor and increase the sensitivity for Th and U. The ICP-MS procedure was compared to the RNAA procedure which we recently developed for the same purpose. Both ICP-MS and RNAA procedures developed were found to yield similar detection limits (sub ppb) for Th and U.     

An improved colorimetric determination of vanadium in geochemical prospecting samples

The colorimetric method employed by the U.S. Geological Survey for the determination of vanadium in large numbers of geochemical prospecting samples has been examined. Use of sodium hydrogen sulphate for fusing the samples avoids precipitation of potassium phosphotungstate during colour development. Sensitivity and selectivity of the method are enhanced by extracting the phosphotungstovanadic acid into isobutyl methyl ketone.     

ICP-OES法测定地球化学样品中的铁

试样采用HCL、HNO3分解,制成2~3%王水溶液。在最佳条件下,用ICP-OES法测定地球化学样品中铁含量,测定范围为0.10~20%。方法简便快速,精密度和准确度能满足分析要求,符合地质矿产实验室测试质量管理规范(区域地球化学普查样品化学成分分析)。适用于地球化学调查样品批量样品中铁的测定,已应用于实际工作中,结果满意。     

Direct flame atomic absorption spectrophotometric determination of alkalis in geochemical samples

Flame atomic absorption spectrometry has been used for the estimation of the alkali metal content (as Na₂O and K₂O) in 95 reference materials with diverse matrices (including recently introduced Polish and Chinese standard samples awaiting certification through collaborative studies) using 1000 μg ml⁻¹ of lanthanum and 2000 μg ml⁻¹ of rubidium as matrix buffers for sodium and potassium, respectively. The ±t (Student's values for the samples with known recommended values (degree of freedom n − 1 = 9), at the 95% and 99% confidence levels) indicate that within the confidence levels 95–99% there is no statistical difference between the data presented and the reference data for most of the samples. The agreement between the reported data and the results obtained are generally good.     

Analyses without calibration curve for determination of indium in sediment and geochemical samples

Influences of atomization temperatures on the characteristic mass and the atomic absorption coefficient of indium were studied. The results show that the values of characteristic mass obtained from the wall, using the platform and the V-shaped boat have appeared to be stable to better than 10, 6 and 12% in the range of 1600–2400 °C, respectively. The determination of indium without calibration curve by furnace with the V-shaped boat using palladium and ammonium salt of EDTA as a matrix modifier are described. The proposed method was applied to the determination of indium in standard sediment and geochemical reference samples and satisfactory results were obtained.     

The determination of gold in geochemical samples by non-dispersive atomic fluorescence spectrometry

Non-dispersive flame atomic fluorescence spectrometry is a very sensitive method for the determination of gold, with a limit of detection in aqueous solution of about 0.5 ng ml^?1. However, the application of the technique to aqua regia digests of geochemical samples is limited by large scatter signals which are due mainly to aluminium. The use of an auxiliary lamp to provide correction for scatter is suitable for samples containing low concentrations of elements which form refractory compounds in the flame or for samples where the full sensitivity of the fluorescence technique is not required. To obtain both high accuracy and sensitivity, gold must be separated from the scattering matrix and this can be achieved by a simple extraction with a 0.1% (w/v) solution of a trioctylmethyl-ammonium salt (Aliquat-336) in di-isobutyl ketone. The use of fluorescence avoids the need for a large extraction ratio and a subsequent washing step to remove iron, as is normally required for atomic absorption measurements.     

The INAA of untreated and water-extracted bone samples

Bone samples /of about 5 mg/ were activated in a nuclear reactor for 1 h. Lines of^87mSr,⁵⁶Mn,²⁴Na,⁴²K,³⁸Cl and⁴⁷Sc /daughter of⁴⁷Ca/ were found in the -ray spectrum. Effects of pre-activation boiling with water and affinities of particular ions for the bone mineral are discussed.     

The application of INAA to the geochemical analysis of single diamonds

Instrumental neutron activation analysis (INAA) has been applied to the analysis of 62 small (0.01–0.5 carat), single, inclusion-bearing and inclusion-free diamonds from South Africa, Brazil and Colorado. Up to 40 elements were detected at the ppb and ppt levels in individual diamonds of the eclogitic (basaltic affinity) and the peridotitic (ultramafic) paragenesis. The data obtained in this study can be used to distinguish between diamonds from the eclogitic and peridotitic parageneses and provides geochemical information on the environment in which diamonds crystallize. Further, the technique may prove to be useful in fingerprinting diamonds of different provenance areas.     

Twin-spray flame atomic-absorption spectrometric determination of antimony, bismuth and mercury in geochemical samples

A new flame atomic-absorption method for determination of antimony, bismuth and mercury, called the twin-spray method, has been established. The operating conditions and potential interferences have been investigated in detail. Under the optimized conditions the sensitivities obtained are 20, 30 and 70 times higher for antimony, bismuth and mercury respectively, than those of conventional AAS. The method can be used to determine as little as 0.00n% of antimony, 0.000n% of bismuth and 0.0n% of mercury in geochemical samples. The procedures are very simple and easy and need no extra apparatus for hydride generation.     

INAA of cortical and trabecular bone samples from animals

Instrumental neutron activation analysis (INAA) was applied to determine Ba, Br, Ca, Cl, Fe, K, Mg, Mn, Na, P, Sr and Zn in bovine and porcine rib bones. Precise results were obtained in analyses of freeze-dried cortical and trabecular bones separately, and also of whole bone ashes. Cortical tissues presented higher concentrations of Ba, Ca, Mg, Mn, Na, P, Sr and Zn than those obtained in trabecular ones. Comparisons were also made between the results obtained for bovine and porcine rib bones. This revised version was published online in August 2006 with corrections to the Cover Date.     

Ion Chromatographic determination of sulfur and chlorine using milligram and submilligram sample weights

Initial results for Ion Chromatographic analyses of chlorine and sulfur in organic compounds combusted by the Schöniger technique show excellent agreement with analyses using standard methods. Samples weighing less than 1 mg can be analyzed if homogeneity is not a problem. Determination of chlorine in the presence of large amounts of bromine and the analysis of other heteroatoms is also possible by IC. The present limiting factor in the microdetermination of chlorine and sulfur by IC is the presence of these species in the filter paper flag.