高精度质谱计在同位素地球化学的应用前景

微量地质样品的高精度同位素比值测试已经成为地质和环境科学等领域极其重要的研究手段.新型固体热电离质谱计以其高精度和高灵敏度, 将在同位素年代学和地球化学领域有广阔的应用前景.报道采用IsoProbeT质谱计测量标准物质溶液的结果.测量锶标准物质NBS987和钕标准物质Ames分别获得平均87Sr/86Sr比值0.710 241 8±0.000 005 1和平均143Nd/144Nd比值0.512 148 4±0.000 002 9, 内部精度可达0.000 3%.微量锶标准物质(0.3~1 ng) 的同位素比值测量内部精度可以优于0.003%.结合低本底化学流程, 实现了微量地质样品的高精度同位素比值测试.这一结合将有效地促进单颗粒矿物年代学和同位素示踪在岩浆岩、变质岩、矿床、构造岩研究的应用.      

通用同位素标准化程序及在Sr、Nd同位素分析上的应用

固体元素的同位素在热表面电离质谱计上分析时,会产生同位素分馏,使得同位素比值测量的重复性和测量精度都受到局限。而在同位素地质学中,有时所遇到的样品之间的同位素比值差别很小,以致被测量过程中的同位素分馏所掩盖,使同位素地质方法的应用受到限制。     

高灵敏度元素分析仪-连续流同位素质谱法对硅酸盐岩中碳及碳同位素组成的精确测定

硅酸盐岩中含有微量的碳,对其精确地分析可以示踪流体的来源和形成过程。元素分析仪-同位素质谱方法(EA-IRMS)是一种使用样品量小、快速的分析方法,本文将EA-IRMS技术应用于硅酸盐岩中微量碳同位素组成的测定,基于一系列条件实验,确认了硅酸盐岩中微量碳分析的EA-IRMS连续流方法的关键条件参数。标准物质选择和归一化处理使用以下方法:(1)选择较宽碳同位素组成范围且合理的碳同位素分布的标准物质,以高纯石英粉末与之混合来模拟天然样品中的基质。(2)利用与样品类似含量的3个标准物质的测量值和标准真值建立校准曲线,对天然样品的测量值进行标准化,从而实现了对硅酸盐岩中低至600!g/g微量碳含量和同位素组成的精确测定。用国家标准物质GBW04416作为未知样品检验了不同含量下拟合的线性方程,在碳含量不低于600!g/g时,标准偏差分别约为0.02‰、0.04‰、0.05‰、-0.07‰、0.11‰;在MERCK+USGS24混合物中,测量的δ13C值在标准误差范围内与理论值是一致的。因此,对于碳含量不低于600!g/g的30 mg硅酸盐岩样品,本方法能够获得高精准度的碳同位素分析结果。根据不同碳含量的标准混合物的峰面积(峰强度)和相对应的含量所建立的线性曲线获得样品的碳含量,碳含量的分析误差在10%以内。     

用双稀释法测定地质样品中的铅同位素组成

随着超净化实验室条件的完善以及多接收同位素质谱技术的成熟，铅同位素双稀释法倍受关注。用双稀释法测定铅同位素比值的方法原理，以及^204Pb—^207Pb双稀释剂的配制和标定方法。通过对标准物质NBS981和地质样品的分析测定，表明用双稀释法测定铅同位素比值，可以有效校正由质谱分析造成的同位素分馏效应，从而提高分析结果的精度和准确度。     

钕同位素比值~(143)Nd/~(144)Nd标准溶液研制

钕同位素比值(~(143)Nd/~(144)Nd)是Sm-Nd同位素方法的关键量值,由于被测样品的~(143)Nd/~(144)Nd比值变化范围很小,所以对~(143)Nd/~(144)Nd比值测试的精准度要求很高(精度优于0.005%)。为了获得高精度和高准确度的测试数据,分析过程中所用Nd同位素标准物质起着重要作用。以往的Nd同位素标准物质都是氧化钕,经过近三十年有的已消耗殆尽。本文阐述了钕同位素比值~(143)Nd/~(144)Nd标准溶液的研制,经检验标准溶液的均匀性和稳定性良好,由11家实验室协同定值,采用MC-TIMS和MC-ICP-MS方法测定~(143)Nd/~(144)Nd,确定了Nd同位素标准溶液的特性值~(143)Nd/~(144)Nd=0.512438,不确定度为5×10-6。此标准溶液于2015年5月获得国家标准样品证书(批号为GSB 04-3258—2015),可被用于地质、资源、海洋、环境、考古等多种样品~(143)Nd/~(144)Nd比值测定时的仪器校准和分析过程的质量监控。     

采用氧化物方式高精度测量微量样品钕同位素比值

微量样品Nd同位素比值的高精度测定在地球科学和环境科学研究中具有重要的意义,同时也是同位素测定的难点.对1ng以下的国际标准样品进行了高精度质谱测试.采用新一代高精度热电离质谱计(IsoProbe-T)分别运用Nd 和NdO 测试方法,多次测量常量(≥200ng)和超微量(0.25ng、0.5ng和1ng)Nd标准物质(Ames、JMC和Jndi-1)和实验室内部标准LRIG-Nd溶液.质谱计同位素比值测量均采用静态多接收模式.143Nd/144Nd比值测量的内部精度均优于0.003%.与传统的Nd 测量方式相比,NdO 测量方式具有显著的优势,即有极高的灵敏度,是Nd 分析灵敏度的100倍左右.     

元素分析仪-同位素比值质谱仪测定海洋沉积物有机碳稳定同位素方法初探

初步建立了利用元素分析仪-同位素比值质谱仪(EA-IRMS)联用技术测定海洋沉积物中有机碳稳定同位素的方法。标定了标准工作参考气CO2(δ13CvsPDB为-32.053‰);验证了仪器的稳定性,标准偏差为0.009‰;当离子流强度范围为0.4～8.7 V时,总体线性为0.0337‰/V,小于仪器线性指标0.06‰/V的要求;同时测定了国家标准物质GBW 04408、国际标准物质Urea和海洋沉积物样品M01的精密度和准确度,标准偏差在0.04‰～0.13‰范围内;并在三家实验室进行了测量比对实验,标准偏差小于0.20‰,满足地质样品再现性0.5‰的要求。所选样品区域δ13Corg范围为-25.29‰～-22.30‰,表明该海域总有机碳是陆源和海源两种来源的混合物。     

大型多接收等离子体质谱测定地质样品的硅同位素

使用Nu Plasma 1700型MC-ICP-MS的高分辨模式并采用标准-样品交叉法(SSB)测定Si同位素比值,以减少质谱干扰和仪器质量歧视对测定结果的影响。结果表明样品与标准样之间的Si浓度差异程度与Si同位素测量值呈正相关关系,样品与标准样的Si浓度差异低于20%时,Si同位素测量值差异小于0.04‰。测试部分国际常用标准样品的Si同位素组成,结果与文献报道值在误差范围内一致,δ~(30)Si测量精度优于0.07‰/amu。     

Helix SFT惰性气体质谱仪分析矿物包裹体中氦同位素组成

氦同位素组成在地球大气圈、地壳及地幔各圈层具有不同的元素丰度和同位素比值,变化范围达数个量级,而且氦作为惰性气体中质量最轻的元素,其稳定性好,迁移能力强,因此将其同位素作为地质过程和物质来源的天然示踪剂倍受重视,被广泛地应用于地学研究的各个领域,而能否对于岩石样品中氦同位素组成进行准确分析,成为了氦同位素作为示踪剂的一个关键问题。本文利用Helix SFT惰性气体质谱仪对岩石矿物包裹体内的氦同位素组成测定方法进行了研究,建立了样品的压碎及气体提取纯化装置,通过进一定体积的标准氦气,计算出仪器的灵敏度,在此基础上对整套系统的静态本底进行了测定。对仪器本身的离子倍增器的接收效率进行了探讨,使其可以准确对3 He进行准确测定。以大气中氦同位素为标准并进行多次测定,获得了氦同位素测量的质量歧视校正因子。通过对实际样品黄铁矿包裹体中氦同位素组成的测定,获得了稳定性很好的同位素比值数据,其精度可达99%。通过建立合理的压碎装置,利用该仪器对氦同位素组成分析的独特优势,可以满足对于岩石矿物包裹体中氦同位素组成的精确测定,满足其在地质科研领域的应用研究需要,进而对基础科学研究起到支撑作用。     

元素分析仪-气体同位素质谱法分析硫酸钙样品的硫同位素组成

硫酸盐硫同位素的常规分析方法是将硫酸盐转化为硫酸钡后搭配双路进样SO2法,该法易于操作、数据稳定,但样品用量大、费时费力,需要繁杂的前处理,无法满足微量分析发展方向的需求。本文以石膏为例,以元素分析仪-气体同位素质谱法(EA-IRMS)直接测定硫酸钙样品硫同位素比值,对同一样品分别采用:①硫酸钙与V2O5混合后包裹于锡杯中密封,直接进行元素分析仪-气体同位素质谱分析;②硫酸钙充分溶于去离子水中,向溶有硫酸钙样品的液体中加入沉淀试剂BaCl2,将生成的硫酸钡沉淀滤出后,用去离子水清洗2~3遍,烘干后与V2O5混合包裹于锡杯中密封再进行质谱测定。实验选取了13件δ34S值变化范围介于-20‰^+30‰之间的天然石膏样品,将获得的硫同位素比值进行对比,二者δ34SV-CDT绝对差值在0.00‰~0.24‰,表明同一样品的硫同位素比值结果在误差范围内基本一致。与常规分析方法相比,本文建立的直接在线分析时无需任何化学前处理,只需直接加入适量的V2O5,V2O5和氧气中的外部氧在瞬间燃烧的过程中替代了硫酸钙本身的氧,生成的SO2气体的氧是均一的,其硫同位素比值能代表样品的硫同位素组成,无需进行氧同位素的校正。经过验证表明,硫酸钙样品的直接在线分析是完全可行的。     

不同检测方法对氢氧同位素分馏的影响

氢氧同位素的检测方法由最初的离线双路进样同位素比质谱法(Dual-inlet IRMS),发展到自动化程度较高的连续流水平衡法(Gasbench-IRMS)检测方法以及现阶段正在研究使用的热转换元素分析同位素比质谱法(TC/EA-IRMS)。为了探讨不同检测方法对氢氧同位素分馏的影响以及各方法的优缺点,文章应用Dual-inlet IRMS、GasbenchⅡ-IRMS、TC/EA-IRMS三种检测方法对四种不同水样的氢氧同位素进行检测,并用国际标准和国家标准对检测结果进行校正。结果表明,Dual-inlet IRMS法检测氢同位素的精密度高,重现性好;Gasbench-IRMS法检测氢同位素的结果重现性较差;Dual-inlet IRMS和Gasbench-IRMS法检测氧同位素要比TC/EA-IRMS法的精密度高,重现性好。用TC/EA-IRMS法检测氢氧同位素,分别用国际标准和国家标准校正,δD值的最大绝对偏差为1.13‰,δ18O值的最大绝对偏差为0.27‰。测定不同水样的氢氧同位素时,连续流GasbenchⅡ-IRMS测定氧同位素较有优势,而TC/EA-IRMS测定氢同位素比较有优势。样品测试过程中选用的校正标准不同,检测结果也存在一定的误差。     

Nitrogen Mass Fraction and Stable Isotope Ratios for Fourteen Geological Reference Materials: Evaluating the Applicability of Elemental Analyser Versus Sealed Tube Combustion Methods

Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g^?1 to 1% m/m nitrogen mass fractions and δ¹⁵N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s).     

水中氢氧同位素不同分析方法的对比

采用在线的连续流Gasbench Ⅱ-IRMS和离线的Dual-inlet IRMS分析方法分析水样中氢氧同位素组成.对比两种分析系统结果表明,运用离线的Dual-inlet IRMS测定氢同位素,精密度均小于1‰,比在线的连续流Gasbench Ⅱ-IRMS重现性和精度好;运用离线的Dual-inlet IRMS和在...     

Intercalibration of Mg Isotope Delta Scales and Realisation of SI Traceability for Mg Isotope Amount Ratios and Isotope Delta Values

The continuous improvement of analytical procedures using multi‐collector technologies in ICP‐mass spectrometry has led to an increased demand for isotope standards with improved homogeneity and reduced measurement uncertainty. For magnesium, this has led to a variety of available standards with different quality levels ranging from artefact standards to isotope reference materials certified for absolute isotope ratios. This required an intercalibration of all standards and reference materials, which we present in this interlaboratory comparison study. The materials Cambridge1, DSM3, ERM‐AE143, ERM‐AE144, ERM‐AE145, IRMM‐009 and NIST SRM 980 were cross‐calibrated with expanded measurement uncertainties (95% confidence level) of less than 0.030‰ for the δ^25/24Mg values and less than 0.037‰ for the δ^26/24Mg values. Thus, comparability of all magnesium isotope delta (δ) measurements based on these standards and reference materials is established. Further, ERM‐AE143 anchors all magnesium δ‐scales to absolute isotope ratios and therefore establishes SI traceability, here traceability to the SI base unit mole. This applies especially to the DSM3 scale, which is proposed to be maintained. With ERM‐AE144 and ERM‐AE145, which are product and educt of a sublimation–condensation process, for the first time a set of isotope reference materials is available with a published value for the apparent triple isotope fractionation exponent θ_app, the fractionation relationship ln α(^25/24Mg)/ln α(^26/24Mg).     

高精度硅同位素分析方法研究进展

基于碱熔法的改进和多接收电感耦合等离子质谱仪（MC-ICP-MS）的发展,近年来高精度Si同位素组成（δ30Si）分析方法取得了长足进步,分析精度（2SD）自气体质谱仪（GS-MS）时代的±0.15‰~±0.30‰ 提高到优于±0.10‰,足以辨析高温过程中Si同位素发生的微小分馏,并且避免了实验流程中使用含氟等危险化学品。二次离子质谱（SIMS）和飞秒激光剥蚀（fs LA）的发展使得原位Si同位素组成分析精度近期也优化到±0.10‰~±0.22‰。文章对近年来Si同位素分析方法的发展沿革进行综述,探讨建立溶液法MC-ICP-MS的高精度Si同位素分析方法的进展与局限,并比对了国内外各个实验室已发表国际国内Si同位素标准物质测定值,最后总结了硅酸盐地球（BSE）、地壳和陨石等主要地质储库的δ30Si组成范围。     

Production and Certification of a Unique Set of Isotope and Delta Reference Materials for Boron Isotope Determination in Geochemical,Environmental and Industrial Materials

Isotopic reference materials are essential to enable reliable and comparable isotope data. In the case of boron only a very limited number of such materials is available, thus preventing adequate quality control of measurement results and validation of analytical procedures. To address this situation a unique set of two boron isotope reference materials (ERM‐AE102a and ‐AE104a) and three offset δ¹¹B reference materials (ERM‐AE120, ‐AE121 and ‐AE122) were produced and certified. The present article describes the production and certification procedure in detail. The isotopic composition of all the materials was adjusted by mixing boron parent solutions enriched in ¹⁰B or ¹¹B with a boron parent solution having a natural isotopic composition under full gravimetric control. All parent solutions were analysed for their boron concentration as well as their boron isotopic composition by thermal ionisation mass spectrometry (TIMS) using isotope dilution as the calibration technique. For all five reference materials the isotopic composition obtained on the basis of the gravimetric data agreed very well with the isotopic composition obtained from different TIMS techniques. Stability and homogeneity studies that were performed showed no significant influence on the isotopic composition or on the related uncertainties. The three reference materials ERM‐AE120, ERM‐AE121 and ERM‐AE122 are the first reference materials with natural δ¹¹B values not equal to 0‰. The certified δ¹¹B values are ?20.2‰ for ERM‐AE120, 19.9‰ for ERM‐AE121 and 39.7‰ for ERM‐AE122, each with an expanded uncertainty (k = 2) of 0.6‰. These materials were produced to cover about three‐quarters of the known natural boron isotope variation. The ¹⁰B enriched isotope reference materials ERM‐AE102a and ERM‐AE104a were produced for industrial applications utilising ¹⁰B for neutron shielding purposes. The certified ¹⁰B isotope abundances are 0.29995 for ERM‐AE102a and 0.31488 for ERM‐AE104a with expanded uncertainties (k = 2) of 0.00027 and 0.00028, respectively. Together with the formerly certified ERM‐AE101 and ERM‐AE103 a unique set of four isotope reference materials and three offset δ¹¹B reference materials for boron isotope determination are now available from European Reference Materials.     

同位素地质样品分析的质量监控与质量评估

讨论了同位素地质样品分析的质量监控与质量评估问题,提出在同位素地质样品分析中以准确度与精度度并重、标准物质监控与重复样监控相结合的质量监控方法。通过对大量标准样品定值数据与积累的测试数据的统计分析,提出了标准物质测定误差和标准偏差及重复样双份分析的双差允许限的确定方法,并采用准确度分数、精密度分数、空白分数和系统性偏倚分数对测试结果的质量进行定量评估的方法,这些方法适用于实验室内部的质量监控和评估     

Ba同位素分析方法综述

随着实验技术的进步以及多接收电感耦合等离子体质谱仪（MC-ICP-MS）和热电离质谱仪（TIMS）的发展,近年来Ba 同位素的分析方法取得了显著进展。分析精度（δ^138/134Ba,2SD）从之前的1 ‰ 提高到好于0.05 ‰。文章综述了近年来高精度Ba 同位素分析方法（溶液法）的发展历程,总结了国内外实验室关于不同类型样品的消解、Ba 元素化学纯化流程以及Ba 同位素质谱测定等方法,并对国内外多个实验室已发表的各类标准物质的Ba 同位素组成进行统计。研究结果可为Ba 同位素激光原位分析提供参考,为后续分馏机理解析和应用研究提供技术支撑。     

High‐Precision,High‐Accuracy Oxygen Isotope Measurements of Zircon Reference Materials with the SHRIMP‐SI

Analytical protocols for SHRIMP‐SI oxygen isotope analysis (δ¹⁸O) of a suite of zircon reference materials (RMs) are presented. Data reduction involved a robust estimate of uncertainties associated with the individual spot as well as for groups where the spot data are combined. The repeatability of δ¹⁸O measurements is dependent on both the analytical conditions and the choice of the primary reference material. Under optimised conditions, repeatability was often better than 0.4‰ (2s) allowing sample uncertainties to be obtained to better than 0.2‰ (at 95% confidence limit). Single spot uncertainty combined the within‐spot precision with the scatter associated with repeated measurements of the primary zircon reference material during a measurement session. The uncertainty for individual spots measured under optimised conditions was between 0.3 and 0.4‰ (at 95% confidence). The analytical protocols described were used to assess a variety of zircon RMs that have been used for geochronology and for which laser fluorination oxygen isotope data are available (Temora 2, FC1, R33, QGNG and Ple?ovice), as well as zircons that have been used as RMs for trace element or other types of determination (Mud Tank, Monastery, 91500, AS57, AS3, KIM‐5, OG1, SL13, CZ3 and several other Sri Lankan zircons). Repeated analyses over nine sessions and seven different mounts show agreement within analytical uncertainty for Temora 2, FC1, R33, QGNG, Ple?ovice and 91500, when normalised to Mud Tank. For existing ion microprobe mounts with these materials, an appropriate δ¹⁸O can be determined. However, care should be taken when using zircons from the Duluth Complex (i.e., FC1, AS57 and AS3) as reference materials as our data indicated an excess scatter on δ¹⁸O values associated with low‐U zircon grains.     

Isotope Ratio Determination in the Earth and Environmental Sciences: Developments and Applications in 2003

This annual review documents developments and applications in the field of isotope ratio determination, as reflected in the literature for the Earth and environmental sciences for the year 2003. Particular emphasis is placed upon the relationship between the two dominant analytical techniques-thermal ionisation mass spectrometry (TIMS) and multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS)-and the rapidly changing nature of their roles in isotope analysis. Additionally, the review covers developments in single-collector ICP-MS and TOF technologies, new sample preparation procedures and the characterisation of isotopic reference materials, together with fundamental investigations of mass spectrometer performance.