Molybdenum Concentrations Measured in Eleven USGS Geochemical Reference Materials by Isotope Dilution Thermal Ionisation Mass Spectrometry

Molybdenum concentrations in eleven USGS geochemical reference materials AGV-1, BCR-1, BHVO-1, BIR-1, DNC-1, DTS-1, G-2, GSP-1, MAG-1, PCC-1 and W-2 were measured by isotope dilution thermal ionisation mass spectrometry (ID-TIMS). In every case but one, the concentrations determined in this study were significantly lower than the current consensus values. Molybdenum concentrations determined by ID-TIMS are inherently more accurate and precisions may be up to an order of magnitude higher than those measured by other analytical techniques.     

High Precision Isotope Dilution Determination of Potassium by Thermal Ionisation Mass Spectrometry

Two independent articles published more than a decade ago pointed to the potential of the somewhat neglected K‐Ca system for very precise K‐Ca dating and thermochronology, but have not been followed up since. In the first of these articles, highly precise determination of K and hence the K/Ca ratio in lunar granites showed the feasibility of K‐Ca dates of micas with an analytical precision known so far in only U‐Pb and Ar/Ar dating. In the second article, it was shown that responses of the K‐Ca and Rb‐Sr isotopic systems in micas subjected to a slow post‐metamorphic cooling could provide new insights into thermochronology. Crucial to the follow‐up of these two promising leads is the development of a simple and user‐friendly method for routine high precision K determination in real samples, such as the one described in this report.     

Boron Determination in Twenty One Silicate Rock Reference Materials by Isotope Dilution ICP-MS

The concentration of boron was determined in twenty one geochemical reference materials (silicate rocks) by isotope dilution inductively coupled plasma-mass spectrometry. Boron was extracted from the rocks using HF digestion, suppressing boron volatilisation through boron-mannitol complexation. Sample solutions, in a diluted HCl matrix, were analysed by ICP-MS without any separation of boron from the matrix elements. The results obtained were in agreement with the literature data and indicate that using the described procedure, trace amounts of boron can be very easily determined in complex matrices with rapidity and precision. With the instrumentation and reagents used in this study, this procedure can be used for the determination of 0.5 μg g⁻¹ boron in a 15 0 mg silicate rock sample. Replicate analyses of the twenty one geochemical reference materials (GRM), ranging in boron concentration from 1.35 to 15 7 μg g⁻¹, yielded precisions (relative standard deviation) varying between 0.9 and 9.8%.     

Determination of Chlorine in Nine Rock Reference Materials by Isotope Dilution Mass Spectrometry

A procedure for the determination of chlorine by the isotope dilution technique (ID) using negative thermal ionisation mass spectrometry (N-TIMS) is described. Silicate samples of about 10 mg were spiked and decomposed with hydrofluoric acid, and chlorine was isolated by precipitation of silver chloride after neutralisation with Ca(OH)₂. The ammonical solution of AgCl was then subjected to N-TIMS. Replicate analyses of rock reference materials, typically of JB-1 and JR-1, demonstrated the high quality of the analyses (precision for Cl was ± 1-2%). We present here the most precise data sets of chlorine concentrations in nine igneous rock reference materials, three basalts (JB-1, JB-2, JB-3), two andesites (JA-3, AGV-1), two rhyolites (JR-1, JR-2) and two granodiorites (JG-3, GSP-1). The chlorine concentrations found ranged from 152 μg g-1 in AGV-1 to 1008 μg g^-1 in JR-1. Our results presented here are partly (but not completely) in agreement with recommended values, where they are available. The N-TIMS ID technique can thus be used as a means of determining low chlorine contents in silicate materials to high precision.     

硅酸盐氧同位素标样研制

本文介绍了硅酸盐氧同位素标准物质(SH和H)的研制。均匀性检验证实该标准物质是均匀的。该标准物质采用直接比较测量法标定,即直接与国际标准V-SMOW和SLAP进行比较。 国际标准水样采用CO_2-H_2O平衡法制备CO_2;石英标样采用BrF_5法制备CO_2。将六个定值实验室提供的数据统一处理后,获得SH和H的δ~(18)Ox/v-s_(MOW)值分别为11.11±0.06(‰)和-1.75+0.08(‰)。该标准物质于89年12月被国家技术监督局批准为国家一级标准物质,山阳石英标样(SH)统一编号为G     

Accurate and Precise Elemental Abundance of Zinc in Reference Materials by an Isotope Dilution Mass Spectrometry TIMS Technique

A thermal ionisation mass spectrometric technique enabled the abundance of Zn in geological and biological reference materials and water samples to be measured by double spiking isotope dilution mass spectrometry enriched in the ⁶⁷Zn and ⁷⁰Zn isotopes. In the past, thermal ionisation mass spectrometry proved to be difficult for low-level zinc isotopic measurements. The size of Zn samples used for isotopic determination, in particular the biological RMs, represents an important breakthrough. These results represent the most accurate and precise concentrations measured for Zn in these samples. The maximum fractional uncertainty was that for TILL-3 (2%), while the minimum fractional uncertainty was 0.7% for both BCR-1 and W-2. The inhomogeneity of Zn in HISS-1 was revealed while other reference materials appeared homogeneous at the 95% confidence uncertainty. The certified concentration of Zn in HISS-1 and IMEP-19 by their producers are 28% and 3.8% higher than the values measured in this work. These are the first Zn concentration measurements in these materials by the isotope dilution-TIMS technique, except for BCR-1, NIES N^o 9 and IMEP-19. Reducing the blank enabled accurate measurement in water at the ng g^-1 level demonstrating the applicability of the technique for low-level Zn samples.     

The Precision and Sensitivity of Thermal Ionisation Mass Spectrometry (TIMS): An Overview of the Present Status

This paper illustrates that sample size cannot be reduced below a theoretical limit and still achieve the highest precision obtainable on modern mass spectrometers. Reproducibility at the few ppm level is achievable and is related essentially to ion counting statistics. The number of atoms necessary to carry out such measurements is related directly to the sensitivity of the instrumentation. As most of the elements of interest are not major constituents of natural silicates, a lower limit to the size of the starting sample is assessed. Even for a number of elements for which very high ion per atom yields are attained by TIMS, minimum sample mass is an important limiting factor for precious or rare samples and may reduce the scientific output of experiments or place a major constraint on the sampling strategy itself. For rare meteorites or individual Martian samples expected to be returned in amounts at the gramme scale for rocks or at the microgramme scale for dust, the high sensitivity of TIMS is a requirement. Nevertheless, a compromise has to be found between sample consumption and the minimal desirable precision for a useful isotopic measurement.     

Determination of In and Sn Mass Fractions in Sixteen Geological Reference Materials by Isotope Dilution MC‐ICP‐MS

Mass fractions of Sn and In were determined in sixteen geological reference materials including basaltic/mafic (BCR‐2, BE‐N, BHVO‐1, BHVO‐2, BIR‐1, OKUM, W‐2, WS‐E), ultramafic (DTS‐2b, MUH‐1, PCC‐1, UB‐N) and felsic/sedimentary reference materials (AGV‐2, JA‐1, SdAR‐M2, SdAR‐H1). Extensive digestion and ion exchange separation tests were carried out in order to provide high yields (> 90% for Sn, > 85% for In), low total procedural blanks (~ 1 ng for Sn, < 3 pg for In) and low analytical uncertainties for the elements of interest in a variety of silicate sample matrices. Replicate analyses (n = 2–13) of Sn–In mass fractions gave combined measurement uncertainties (2u) that were generally < 3% and in agreement with literature data, where available. We present the first high‐precision In data for reference materials OKUM (32.1 ± 1.5 ng g^?1), DTS‐2b (2.03 ± 0.25 ng g^?1), MUH‐1 (6.44 ± 0.30 ng g^?1) and PCC‐1 (3.55 ± 0.35 ng g^?1) as well as the first Sn data for MUH‐1 (0.057 ± 0.010 μg g^?1) and DTS‐2b (0.623 ± 0.018 μg g^?1).     

The Calcium Isotope Composition of Modern Seawater Determined by Thermal Ionisation Mass Spectrometry

The Ca isotopic composition of modern seawater has been determined using a ⁴³Ca-⁴⁸Ca double spike, which was calibrated using a ⁴²Ca/⁴⁴Ca seawater ratio of 0.30587 ± 0.00026. This ratio was determined from a total evaporation experiment in which the ion beam was measured from the beginning to the end of the emission. With integration of the peak intensities, the fractionation effects can be minimised, since total evaporation of the reservoir cancels out the effect of vapour enrichment in the light isotopes. This experiment avoids the gravimetric uncertainty inherent in the double spike calibration. This calibration allows the precise redetermination of the seawater isotopic composition of Ca. A mean ⁴⁰Ca/⁴⁴Ca ratio for two Atlantic water samples of 45.143 (2s_mean= 0.003) was found. The good reproducibility of the Ca isotope ratios in present seawater and the very strong isotopic homogeneity of Ca in the oceans illustrate the advantage of using seawater as the common standard, with the advantage of decreasing interlaboratory bias.     

Multi-Element Isotope Dilution Sector Field ICP-MS: A Precise Technique for the Analysis of Geological Materials and its Application to Geological Reference Materials

We present a multi-element technique for the simultaneous determination of twelve trace elements in geological materials by combined isotope dilution (ID) sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) following simple sample digestion. In addition, the concentrations of fourteen other trace elements have been obtained using the ID determined elements as internal standards. This method combines the advantages of ID (high precision and accuracy) with those of SF-ICP-MS (multi-element capability, fast sample processing without element separation) and overcomes the most prevailing drawbacks of ICP-MS (matrix effects and drift in sensitivity). Trace element concentration data for BHVO-1 (n = 5) reproduced to within 1–3% RSD with an accuracy of 1–2% relative to respective literature values for ID values and 2–3% for all other values. We have applied this technique to the analysis of seventeen geological reference materials from the USGS, GSJ and IAG. The sample set also included the new USGS reference glasses BCR-2G, BHVO-2G and BIR-1G, as well as the MPI-DING reference glasses KL2-G and ML3B-G, and NIST SRM 612. Most data agreed within 3–4% with respective literature data. The concentration data for the USGS reference glasses agreed in most cases with respective data of the original rock powder within the combined standard uncertainty of the method (2–3%), except the U concentration of BIR-1G, which showed a three times higher concentration compared to BIR-1.     

同位素稀释等离子体质谱法测定岩石中的铂

报道了以普通铂标准溶液标定198Pt稀释剂溶液的浓度,采用同位素稀释等离子体质谱法测定岩石中的Pt。稀释剂标定结果得到该198Pt稀释剂溶液的浓度为19.76μg/g(n=4,RSD=0.16%)。4次测定标准物质GBW07293(取样量约0.5g,推荐浓度440±37ng/g)中Pt含量,结果分别为412.0±2.6ng/g、495.9±2.7ng/g、519.6±3.5ng/g和677.3±3.8ng/g。单份试样重复测量的相对标准偏差<1%。由于铂族元素的块金效应,各份平行测定的结果较分散。     

低质量数元素同位素在线连续流同位素比值质谱分析的质量控制和数据标准化

同位素比值质谱分析方法是准确测量各种同位素相对丰度的标准方法。连续流同位素质谱的出现不仅提高运行效率,也降低了样品用量并提高灵敏度。但是,要使这种方法获得更好准确度和精度的同位素数据,并做到所获得数据可与其他实验室结果进行类比,从而得到可靠的同位素数据,这就需要好的分析策略和运行方案,还需要对仪器日常性能和数据质量进行严密的监视管控,而且还取决于原始数据如何进一步标准化到国际同位素尺度上。因此,同位素比值质谱结合元素分析仪(或热转换元素分析仪)连续流方法要实现可靠的稳定同位素分析需要:①设备安装和环境控制、测试准备、样品制备和称量、标准物质选择及序列等规范化质量控制措施;②严格校准仪器系统(包括调节灵敏度和线性,背景值监测,稳定性检测,H+3系数校正等);③可靠的数据处理。目前不同的实验室,采用标准物质来标定系统、对测量的同位素数据进行标准化,以及利用控制曲线来监测系统稳定性并对不确定度的计算,这些策略往往都不同。因此,统一的数据处理方案是被高度期待的。目前最好的执行方案是基于线性回归的两点或多点标准化方法。如果每一批样品中测量两个不同的标准物质四次,或者测量四个标准物质两次,那么不确定度会降低50%。当前同位素比值质谱能够测定同位素比值的不确定度一般要好于0.02‰。但是,标准物质的使用既要考虑样品的性质,同时要涵盖它们未知同位素组成的范围,尤其氢同位素在现阶段缺乏标准物质和测量的仪器精度较差(比碳、氮、氧等要低一个数量级)的情况下,这显然是稳定同位素分析者的一个重大挑战。本文概括了同位素比值质谱结合元素分析仪(或热转换元素分析仪)的基本操作原理和分析实践,将数据处理运用到同位素比值分析之中,获得连续流同位素比值质谱分析结果的合理准确度和精度。     

Multi-collector ICP-MS Analysis of Pb Isotope Ratios in Rocks: Data, Procedure and Caution

The authors measured Pb isotope compositions of seven USGS rock reference standards, i.e. AGV-1, AGV-2, BHVO-1, BHVO-2, BCR-2, BER-1/1 and W-2, together with NBS 981 using a micromass isoprobe multi-collector inductively-coupled plasma mass spectrometer (MC-ICP-MS) at the University of Queensland. 203Tl-205Tl isotopes were used as an internal standard to correct for mass-dependant isotopic fractionation. The results for both NBS 981 and USGS rock standards AGV-1 and BHVO-1 are comparable to or better than double- and triple-spike TIMS (thermal ionization mass spectrometry) data in precision. The data for BHVO-2 and, to a lesser extent, AGV-2 and BCR-2 are reproducibly higher for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb than double-spike TIMS data in the literature. The authors also obtained the Pb isotope data for BIR-1/1 and W-2, which may be used as reference values in future studies. It is found that linear correction for Pb isotopic fractionation is adequate with the results identical to those corre     

直接熔融热电离质谱法测定硼硅玻璃中硼同位素比值

硼硅玻璃是目前压水堆应用最多的可燃毒物材料,产品中硼同位素组成的准确测定对燃耗预估及产品质量判定具有重要意义。文章基于直接熔融热电离质谱法,首先探讨了硅元素对硼酸中硼同位素测量结果的影响,结果表明:Si/B质量比小于9时,硅对NIST 951a硼酸标准物质测量结果无显著干扰,采用直接熔融热电离质谱法测定核电用硼硅玻璃中硼同位素比值具有可行性;随后,详细分析了Na/B摩尔比、甘露醇和石墨加入量3个参数对测试结果的影响,得到的最佳参数为Na/B摩尔比9、加入甘露醇及3μL石墨发射剂;最后,采用优化测试参数,对实际硼硅玻璃样品进行了测试,并以NIST 951a硼酸标准物质为外标对测量结果进行分馏校正,结果发现分馏校正后样品的不确定度来源主要是标准物质。研究成果可满足硼硅玻璃的燃耗预估及产品质量的快速判定需要。     

Determination of Chromium, Nickel, Copper and Zinc in Milligram Samples of Geological Materials Using Isotope Dilution High Resolution Inductively Coupled Plasma-Mass Spectrometry

A simple and accurate method for the determination of Cr, Ni, Cu and Zn at μg g^?1 levels in milligram‐sized bulk silicate materials is reported using isotope dilution high‐resolution inductively coupled plasma‐mass spectrometry (HR‐ICP‐MS) with a flow injection system. Silicate samples with Cr, Ni, Cu and Zn spikes were digested with HF‐HBr and Br₂, and subsequently decomposed at 518 K in a Teflon bomb. In this procedure, all sulfides and chromite, major hosts of these elements, were completely decomposed, thus allowing for isotope equilibration between the sample and spike. Magnesium and Al fluorides formed after the digestion of the sample were removed by centrifugation, and the supernatant was directly aspirated into a HR‐ICP‐MS at a mass resolution of 7500, where interfering oxide ions, ArO⁺, CaO⁺, TiO⁺, CrO⁺ and VO⁺, were separated from Cr⁺, Ni⁺, Cu⁺ and Zn⁺. No matrix effects were observed down to a dilution factor of 50. Detection limits for these elements in silicate samples were < 0.04 μg g^?1. The effectiveness of the technique was demonstrated by the analysis of 13 to 40 mg test portions of USGS and GSJ silicate reference materials with a major element composition ranging from andesite to peridotite, in addition to 8‐23 mg of the Smithsonian reference Allende. Both the reproducibility and the deviation from the reference value for most reference materials of various rock types were < 9%, and thus confirm that the method gives accurate analytical results for small sample sizes over a wide range of Cr, Ni, Cu and Zn contents. This method is, therefore, suitable for analysing small and/or precious bulk samples, such as meteorites, mantle peridotites and mineral separates, and for the characterisation of silicate and sulfide minerals for use as calibration samples in secondary ion mass spectrometry or laser ablation ICP‐MS.     

Evaluation of Simultaneous Analyte Leaching/Vapour Phase Introduction for Direct Osmium Isotope Ratio Measurements in Solid Samples by Double-Focusing Sector Field ICP-MS

The analytical performance of a method for Os isotope ratio measurement by double‐focusing, sector field ICP‐MS (ICP‐SFMS) was evaluated. The method is based on several optimised, concurrent processes: Os extraction from samples in hot concentrated nitric acid; separation of Os from the digest solution by the formation of volatile osmium tetroxide accelerated by continuous hydrogen peroxide addition; transport of analyte vapour by an oxygen flow into the ICP; and isotopic determination by ICP‐SFMS. Due to the very efficient utilisation of analyte (approaching 0.5‰), Os isotope ratio measurement could be performed at low pg levels. Combined with an ability to process sample sizes up to 2 g (up to 50 g if the organic matrix of biological or botanical samples is eliminated by ashing), materials with Os concentrations in the low, or even sub pg g^?1 range could be determined by this method. Given that two complete digestion/distillation systems were available for interchangeable use, throughputs of up to fifteen samples per 8 hour shift could be achieved. The method precision, evaluated as the long‐term reproducibility of ¹⁸⁷ Os/¹⁸⁸Os ratio measurements in a commercial Os reference sample containing 0.5 ng Os, was 0.16% relative standard deviation (RSD, 1s). The method has been applied to perform replicate ¹⁸⁷ Os/¹⁸⁸ Os ratio measurements on a suite of fifty reference materials of various origins and matrix compositions, with Os concentrations varying from < 0.1 pg g^?1 to > 100 ng g^?1, yielding an average precision of 3% RSD. Though none of the materials tested are certified for Os content or Os isotope composition, comparison of the obtained data with published Os isotope information for similar sample types revealed close agreement between the two. The method can also be used for the simultaneous, semi‐quantitative determination of Os concentrations.     

Problems of Lithium Isotope Research in Salt Lake Study

正Lithium in nature mainly exists in the forms of solid minerals and ionic liquid.More than 150 lithium minerals exist,which are mainly pegmatite mineral including triphane,lithionite and petalite.Liquid lithium mainly     

Development of Synthetic Clinopyroxene Reference Materials for In Situ Lithium Isotope Measurement by LA-MC-ICP-MS

The isotopic composition of lithium (Li) in clinopyroxene (Cpx), determined via in situ micro-analysis, has been employed as a potential geochemical tool for studying various geological processes such as crust-mantle recycling, silicate weathering and fluid-rock interaction. To obtain precise and accurate Li isotopic compositions in Cpx by LA-MC-ICP-MS, synthetic Cpx matrix-matched reference materials (RMs) were prepared in this study. Six Cpx-matrix RMs were prepared by mixing metallic oxides with GSP-2 (granodiorite) or pure L-SVEC solution and melting them into glasses (GSP-2 + oxide; L-SVEC + oxide). Two representative synthetic glasses, CPXA01 and CPXB01, were subjected to a series of analyses to investigate the possible qualification of the RMs for in situ Li isotope measurement by LA-MC-ICP-MS, including elemental homogeneity analysis (elemental mapping analysis and spot analysis), Li isotopic homogeneity analysis and accurate Li isotopic determination. The applicability of the synthetic Cpx-matrix RMs was highlighted by comparing the δ⁷Li values of three natural Cpx calibrated against the synthetic Cpx-matrix RMs and other commonly used RMs with different matrices (NIST SRM 612, BCR-2G, GOR128-G, StHs6/80-G, KL2-G and T1-G), respectively. Additionally, CPXB01-05 RMs with the same matrix but different Li contents were prepared to explore the Li content mismatch effect, which is significant for accurate determination of in situ Li isotopic composition by LA-MC-ICP-MS. The results of the cross-calibration of Li isotopes in CPXA01 and CPXB01 suggested no obvious Li isotopic fractionation between the two types of glasses (GSP-2 + oxide; L-SVEC + oxide). Thus, the two methods of producing Cpx-matrix RMs are suitable for preparing the matrix-matched RMs for in situ microanalysis for Li isotopes.     

Calcium Isotopic Fractionation during Ion‐Exchange Column Chemistry and Thermal Ionisation Mass Spectrometry (TIMS) Determination

Significant isotopic fractionation can occur during column chemistry and determination by mass spectrometry. Improper correction may produce uncertainties in the isotopic composition of geological samples. We investigated calcium isotopic fractionation during these two processes and set up a model to check data quality. The δ^44/40Ca_915a value of IAPSO seawater in different Ca cuts (e.g., 0–20, 20–40, 40–60, 60–80 and 80–100%) on column chemistry ranged from ~ 4‰ to 0‰. The more Ca was eluted, the lower the δ^44/40Ca_915a value of the elution was found. The isotopic fractionation of calcium on the column appeared to follow the exponential law. However, TIMS instrumental fractionation during Ca runs did not always follow the exponential law due to mixing effects from sample reservoirs on the filament. Our results show that errors could be caused if the instrumental fractionation deviates from the exponential law, especially when the fractionation degree is large. To improve the measurement uncertainty, a model is proposed to check the behaviour and degree of instrumental fractionation, which will provide a quick and reasonable verdict on the data quality of TIMS runs.