Determination of trace elements in silicate rocks by X-ray fluorescence spectrometry on 1:5 glass discs: comparison of accuracy and precision with pressed powder pellet analysis

A fusion procedure commonly used for major element analysis of silicate rocks (1:5 sample to flux ratio, using 0.7 g of sample) was used to determine a small group of trace elements (Cu, Zn, Rb, Sr, Y, Zr, Nb) by X-ray fluorescence. Compton scatter peak ratioing was successfully used for matrix corrections, despite the thickness of the glass discs being only 1.7 mm. Precision and detection limits were compared with pressed pellet values. For most elements, routine analytical precision is better with powder pellets and detection limits are worse in glass discs, by an average factor of 2, considering all elements analyzed. Accuracy was evaluated with international reference materials and for most of the determinations, good or excellent agreement with recommended values was obtained. The main advantages of using glass discs for the trace element determination are the possibility of analyzing small amounts of sample and the suppression of any mineralogical effects in the glass discs, which can also be used to determine major elements.     

Routine Control of Accuracy in Silicate Rock Analysis by X-Ray Fluorescence Spectrometry

In this study, we used the modified Horwitz expression (H_c= 0.01c^0.8495, which gives the precision as a function of concentration) to evaluate and control the accuracy of results of silicate rock analysis obtained by X-ray fluorescence spectrometry. This expression is currently used by the organisers of the GeoPT international proficiency tests, to assign the precision limits of each analyte and subsequently to evaluate the data provided by laboratories whose main application is geochemistry. Results for major and trace elements, determined in glass disk and pressed pellets, respectively, were evaluated. Nine international silicate rock reference materials were analysed and results were compared to the recommended values plus and minus the limits given by the above expression. Those limits are easily attained for most major elements, but not for trace elements. Sample preparation and sub-sampling contributions to precision were evaluated by analysis of an in-house reference sample. In our results, precision does not follow the Horwitz expression relationship with concentration. It is known that the final accuracy in XRF analysis depends strongly on instrumental settings and on the uncertainties associated with the certified or recommended values of the reference materials used to calibrate the spectrometer, but our results indicate that the precision expression can be useful, especially to inspect and correct calibration curves and to check routine instrumental accuracy.     

Format and philosophy for collecting,compiling, and reporting microprobe monazite ages

Microprobe monazite dating has been increasingly used to constrain the timing of deformation and metamorphism because of the potential to date very small monazite domains (down to 5 μm or less) in structural and petrologic context. This paper presents an analytical strategy, presentation format, and error considerations for microprobe monazite dating. The strategy involves high-resolution compositional mapping to delineate compositional domains within monazite crystals. Then for each compositional domain, a series of Th, U and Pb analyses are made, and a single date and error are calculated. The number of analyses in each domain is determined by the desired statistical precision of the date. Results from several monazite grains are typically combined and, along with textural relationships, are used to build an argument that the dates constrain the age of a deformation or metamorphic event. The total error involves three components: short-term random error (dominated by counting statistical uncertainty), short-term systematic error (uncertainty in background correction, conductive coating variation, and calibration), and long-term systematic error (uncertainty in standard composition, mass absorption factors, decay constants, etc.). In homogeneous compositional domains, short-term random errors (2σ) of less than 10 m.y. can be obtained from five to ten analyses. However, short-term systematic error, mainly background estimation uncertainty, would typically result in a doubling of the magnitude of random error. Microprobe dates are presented as a single Gaussian probability distribution for each domain, along with representative compositional maps. It is recommended that a consistency standard be analyzed during each analytical session and the results be reported along with those from the unknown. This proposed strategy and format are compatible with those of other geochronological techniques; they incorporate analytical limitations associated with trace, as opposed to major element, microprobe analysis, and will allow better comparisons to be made between labs and between different geochronological techniques.     

A Simple Method for Precise Determination of 23 Trace Elements in Granitic Rocks by ICP-MS after Lithium Tetraborate Fusion

Abstract. An improved alkali fusion method followed by HF-HNO₃-HC1O₄ treatment is performed for simultaneous determination of 23 trace elements (Sr, Y, Zr, Nb, Ba, Hf, Ta, Th, U, and REE) by ICP-MS in rock reference materials: basaltic rocks (JB-2, JB-3) and granitic rocks (JG-la, JG-2, JG-3). Our improved method offers several advantages including: (1) suppression of whitish precipitates probably composed of insoluble fluorides by addition of HCIO4, (2) simple and reliable preparation procedure, (3) instrument calibration which enables straightforward simultaneous multi-elemental analysis, and (4) the very low background levels by using pure lithium tetraborate flux. We obtained the analytical results with a reproducibility of mostly <2 % (1) for the basaltic rocks and <7 % for the granitic rocks. The higher relative standard deviation (RSD) values for granitic rocks may be attributed to sample heterogeneity of coarse-grained granitic rocks. The analytical results of the granitic rocks demonstrate that Zr and Hf abundances are consistent with the compiled values and that REE concentrations agree well with recently published data, suggesting that the Li₂B₄O₇ fusion method applied in the present study is suitable for the analysis of the granitic rocks.     

Trace Element Analysis of Fused Whole-Rock Glasses by Laser Ablation-ICP-MS and PIXE

The concentrations of fifty trace elements, including relatively volatile elements and transition metal elements, in fused glasses of Geological Survey of Japan rock reference materials GSJ JR-2, JA-1, JA-2, JB-1a, JB-3, JGb-1 and JF-1 were determined by particle (proton) induced X-ray emission (PIXE) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The fused glasses were prepared by rapid fusion and subsequent quenching in welded platinum capsules and were found to be homogeneous for major elements and for trace elements with concentrations of more than 1 μg g^-1 within the observed precision (± 10% mean) on a 70 μm sampling scale. The values obtained by PIXE and LA-ICP-MS for the transition elements (Cr, Mn, Fe, Ni and Cu), the relatively volatile elements (Zn, Ga, Rb and Pb) and the refractory elements (Y, Zr, Nb and Th) with concentrations greater than a few μg g^-1 showed good agreement (within 10 % relative difference). The values for almost all the elements detected at concentrations higher than 1 μg g^-1 as determined by LA-ICP-MS also agreed well with the reference values (mean relative difference < ± 10%), except for B and Cu. The good agreement confirmed the appropriateness of the NIST SRM 600 series glass calibration reference material for LA-ICP-MS analysis of glasses with variable major-element compositions for almost all elements. The concentrations of Cu in all the samples were lower than the reference values, which was attributed to adsorption of the transition metals onto the platinum capsule during preparation.     

Determination of Platinum-Group Elements in Geological Reference Materials by High Resolution-ICP-MS after Nickel Sulfide Fire-Assay Collection and Te Co-Precipitation

Inductively coupled plasma-mass spectrometry (ICP-MS) after NiS fire assay-Te co-precipitation was employed in the determination of Ru, Rh, Pd, Os, Ir and Pt at ng g^-1 levels in six platinum-group element (PGE) geological reference materials. In general, the average of several results was in good agreement with the certified values taking into account respective uncertainties. High relative standard deviations were observed for the reference materials GPt-3 and GPt-4. Problems associated with the NiS fire assay procedure and PGE determination at the sub-10 ng g^-1 level are reviewed and discussed.     

SIMS Determination of μg g−1-Level Fluorine in Geological Samples and its Concentration in NIST SRM 610

The fluorine concentration in NIST SRM 610 was determined by SIMS to be 295 16 μg g⁻¹ (5.40% relative standard deviation). Accuracy of the measurement was determined from a calibration involving the synthesis of glass calibration samples doped with varying concentrations of fluorine and characterized by electron microprobe analysis and SIMS. The calibration was accurate to about 5%. Multiple analyses of the calibration samples and SRM 610 in three different analytical sessions combine to produce a low relative standard deviation of the mean (0.23% RSD) in the mean fluorine value for SRM 610. Analytical uncertainty in the fluorine value was 5.40% (RSD), originating from a combination of calibration and ion counting uncertainties as determined from multiple analyses. Evaluation of the SIMS technique using the new fluorine value in SRM 610 shows that this element can be determined with a precision and accuracy superior to that of EPMA. Measurements of fluorine in igneous and hydrothermal zircon suggest that F-ligands may have been responsible for Zr transportation in hydrothermal fluids also responsible for W-Au mineralisation. Other applications for low-level fluorine determinations may include melt inclusions and nominally anhydrous mineral phases, particularly mantle phases.     

基于X射线荧光光谱法测定常见生物样品中常量和微量元素

基于大米、小麦、玉米等23种国家生物成分系列标准物质,探讨了X射线荧光光谱法在常见生物样品中常量和微量元素测定中的应用。在对各待测元素的激发电流电压、分析线、背景位置、干扰谱线、分析晶体、准直器、探测器和脉冲高度分布等条件进行分析的基础上,采用粉末压片法制样,基于回归曲线法和康普顿散射线内标法求取各待测元素的标准曲线常数、元素间吸收效应的影响系数和谱重叠系数。结果表明:国家生物成分系列标准物质具有足够宽的含量范围和适当的含量梯度,基本能覆盖常见生物样品中各元素的含量范围。方法检出限能够保证测定结果的有效性,测量精密度为2.62%～14.79%,且标准物质各元素的测定值与标准值基本相符。方法具有简便、灵敏和准确的特点,能够满足分析的需求。     

Multi-Element Analysis of Fifty-Four Geochemical Reference Samples Using Inductively Coupled Plasma-Atomic Emission Spectrometry

Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) has been applied for simultaneous, multielement analysis of a diverse suite of igneous rocks and minerals, metamorphic and sedimentary rocks, coals and soils using a single matrix calibration procedure and a single sample preparation. Analytical results determined on 40 elements in 54 geochemical reference samples are presented. A sample analysis time of about three minutes allows the analyst to run several hundred samples per day, but does not include sample dissolution. The instrumental method described here provides the capability for rapid, simultaneous, multielement determination of the major (except silica), minor, and trace elements in rocks using a single sample preparation technique. Analytical data collected on the Geochemical Reference Samples (GRS) demonstrate the general utility of the method. Analytical results show an excellent agreement with previously published results for the major and minor elements. Of the 28 trace elements studied, 17 can be routinely determined in crustal rocks, but the concentration of several of the others can be determined only if present at concentrations several times above their crustal-abundance level.     

Preparation of a Synthetic Titanite Glass Calibration Material for In Situ Microanalysis by Direct Fusion in Graphite Electrodes: A Preliminary Characterisation by EPMA and LA-ICP-MS

This paper describes a technique for the preparation of a titanite (CaTiSiO₅) glass calibration material for use in in situ microanalysis of major, minor, and trace elements in geological materials. The starting composition was a titanite matrix doped with minor and trace elements at ∼ 200 μg g^-1. The elements Sc, Y, REEs, Th and U were added in the form of nitrates in solution, and the elements V, Cr, Mn, Fe, Co, Ni, Zr, Nb, Hf and W were added as solid oxides. The synthetic titanite glass was produced by direct fusion by resistance heating in graphite electrodes at 1600-1700 °C, and quenched in air. Backscattered electron images indicate good homogeneity, with no signs of separate phases or vesicles, and analysis of the major elements Ca, Ti and Si by electron microprobe showed relative standard deviations between 0.5 and 0.7%, based on six independent measurements. Deviations from nominal concentrations for Ca, Si and Ti were measured to -1.2, -3.3 and -0.8%, respectively. The homogeneity of the trace elements in the glass was assessed by LA-ICP-MS analyses, using NIST SRM 610, 612 and 616 as external calibrators, and Ca as the internal standard element. Determinations were made both with a quadrupole mass spectrometer and a sector field instrument, and both raster and spot modes of analysis were used. For the majority of doped elements, precision was better than 10%, and relative deviations from nominal values were, with few exceptions, between 5 and 10%.     

High‐Precision Iron Isotope Analysis of Geological Reference Materials by High‐Resolution MC‐ICP‐MS

We report high‐precision iron isotopic data for twenty‐two commercially available geological reference materials, including silicates, carbonatite, shale, carbonate and clay. Accuracy was checked by analyses of synthetic solutions with known Fe isotopic compositions but different matrices ranging from felsic to ultramafic igneous rocks, high Ca and low Fe limestone, to samples enriched in transition group elements (e.g., Cu, Co and Ni). Analyses over a 2‐year period of these synthetic samples and pure Fe solutions that were processed through the whole chemistry procedure yielded an average δ⁵⁶Fe value of ?0.001 ± 0.025‰ (2s, n = 74), identical to the expected true value of 0. This demonstrates a long‐term reproducibility and accuracy of < 0.03‰ for determination of ⁵⁶Fe/⁵⁴Fe ratios. Reproducibility and accuracy were further confirmed by replicate measurements of the twenty‐two RMs, which yielded results that perfectly match the mean values of published data within quoted uncertainties. New recommended values and associated uncertainties are presented for interlaboratory calibration in the future.     

Platinum-Group Elements and Gold Determination in NiS Fire Assay Buttons by UV Laser Ablation ICP-MS

The direct analysis of nickel sulfide fire assay buttons by UV laser ablation ICP-MS was used to determine the platinum-group elements and gold in the following reference materials: UMT-1, WPR-1, WMG-1, GPt-4, GPt-6 and CHR-Bkg. The instrument was calibrated with buttons prepared using quartz doped with the appropriate standard solutions. Analytical precision (RSD) was generally better than 10%, although occasional higher RSDs may infer local heterogeneities within nickel sulfide buttons. Good or excellent agreement was observed between analysed and reference material values except Rh in UMT-1 and WMG-1, which suffered an interference from copper. Detection limits calculated as 10 s quantitation limits were Au (1.7 ng g⁻¹), Pd (3.3 ng g⁻¹), Pt (8.3 ng g⁻¹), Os (1.3 ng g⁻¹), Rh (1 ng g⁻¹), Ru (5 ng g⁻¹) and Ir (0.7 ng g⁻¹).     

Analysis of Re, Au, Pd, Pt and Rh in NIST Glass Certified Reference Materials and Natural Basalt Glasses by Laser Ablation ICP-MS

A new technique for the in situ analysis of Re, Au, Pd, Pt and Rh in natural basalt glass by laser ablation (LA)-ICP-MS is described. The method involves external calibration against NIST SRM 612/613 or 614/615 glass certified reference materials, internal standardisation using Ca, and ablation with a 200 μm wide beam spot and a pulsed laser repetition rate of 50 Hz. Under these conditions, sensitivities for Re, Au, Pd, Pt and Rh analyte ions are ˜ 5000 to 100,000 cps/μg g^-1. This is sufficient to make measurements precise to ˜ 10% at the 2-10 μg g^-1 level, which is well within the range of concentrations expected in many basalts. For LA-ICP-MS calibration and a demonstration of the accuracy of the technique, concentrations of Re, Au, Pd, Pt and Rh in the NIST SRM 610/611 (˜ 1 to 50 μg g^-1), 612/613 (˜ 1 to 7 μg g^-1), 614/615 (˜ 0.2 to 2 μg g^-1) and 616/617 (˜ 0.004 to 2 μg g^-1) glasses were determined by solution-nebulisation (SN)-ICP-MS. Using the 612/613 or 614/615 glasses as calibration standards, LA-ICP-MS measurements of these elements in the other NIST glasses fell within ˜ 15% of those determined by SN-ICP-MS. Replicate LA-ICP-MS analyses of the 612/613 and 614/615 glasses indicate that, apart from certain anomalous domains, the glasses are homogeneous for Re, Au, Pd, Pt and Rh to better than 3.5%. Two LA-ICP-MS analyses of natural, island-arc basalt glasses exhibit large fractionations of Re, Au and Pd relative to Pt and Rh, compared to the relative abundances in the primitive mantle.     

X射线荧光光谱熔融制样法测定钛铁矿中主次量组分

采用熔融玻璃片法制样，X射线荧光光谱法测定钛铁矿中Fe、Ti、Si、Al、Ca、Mg、Mn、P、S、V和Cr等11种主次量组分。探讨了熔融钛铁矿的有效熔剂，认为Li2B4O7和Li2CO3混合熔剂效果好。方法用于钒钛磁铁矿等国家一级标准物质的测定，结果与标准值相符，对主、次量组分方法精密度（RSD，n=10）为0．20％～9．10％。     

A Flux‐Free Fusion Technique for Rapid Determination of Major and Trace Elements in Silicate Rocks by LA‐ICP‐MS

A simple flux‐free fusion technique was developed to analyse major and trace element compositions of silicate rocks. The sample powders were melted in a molybdenum capsule sealed in a graphite tube to make a homogenous glass in a temperature‐controlled one‐atmosphere furnace. The glass was then measured for both major and trace element concentrations by LA‐ICP‐MS using a calibration strategy of total metal‐oxide normalisation. The optimum conditions (i.e., temperature and duration) to make homogeneous glasses were obtained by performing melting experiments using a series of USGS reference materials including BCR‐2, BIR‐1, BHVO‐2, AGV‐1, AGV‐2, RGM‐1, W‐2 and GSP‐2 with SiO₂ contents from 47 to 73% m/m. Analytical results of the USGS reference materials using our method were generally consistent with the recommended values within a discrepancy of 5–10% for most elements. The routine precision of our method was generally better than 5–10% RSD. Compared with previous methods of LA‐ICP‐MS whole‐rock analyses, our flux‐free fusion method is convenient and efficient in making silicate powder into homogeneous glass. Furthermore, it limits contamination and loss of volatile elements during heating. Therefore, our new method has great potential to provide reliable and rapid determinations of major and trace element compositions for silicate rocks.     

Limitations of chemical dating of monazite

Instrumental and spectral characteristics germane to chemical dating of monazite have been tested using the Cameca SX-100 at Rensselaer Polytechnic Institute. Statistical analysis demonstrates that, for trace element analysis, equal counting time on peak and background is required for optimal statistical precision, thus rendering impractical the procedure of fitting the entire spectrum to obtain background values. Energy shifts require shifting the detector voltage window between peak and background positions, and it is concluded that the differential auto PHA mode works optimally for this.Analyses of Pb-free phosphates, silicates, and oxides are used to measure spectral interferences with the PbM_α peak and background positions. Backgrounds were modeled using both linear and exponential fits. It was found that the difference in background counts using the two fits varies with each of the five spectrometers examined, and that the high-pressure (3 bar) detectors show larger differences in exponential vs. linear peak-minus-background (P-B) values than the low-pressure (1 bar) detectors. In addition, every spectrometer requires a unique correction for every major element in monazite. An analytical protocol is presented that incorporates these results. This protocol was applied to several monazite standards to determine inter-spectrometer variability, and spectrometer reproducibility from session to session. It was found that the difference in composition (and age) between spectrometers on identical spots exceeds the 2 sigma standard error of the mean of composition (or age) on either spectrometer. This means that (a) additional sources of error beyond the counting statistics exist between spectrometers; (b) the precision of microprobe ages cannot be continuously improved by additional counting; and (c) the minimum realistic precision is on the order of ± 2–3% for monazites with around 1500–2000 ppm total Pb, or an additional absolute uncertainty of 20–50 ppm Pb.     

电感耦合等离子体发射光谱法测定电子电器和玩具无铅焊锡中银的不确定度评定

建立了电感耦合等离子体发射光谱法测定无铅焊锡中银的数学模型,对数学模型中各个参数的不确定度来源进行评定,包括称样质量、配制标准工作溶液、工作曲线拟合、试液定容体积及测量重复性等引入的不确定度。计算检测结果的合成标准不确定度为0.02%,扩展不确定度为0.04%。     

X射线荧光光谱法快速分析镁质耐火材料中硅铝铁钛钙镁

采用X射线荧光光谱法快速测定镁质耐火材料（包括原料镁砂及其制品镁砖）中的SiO₂、Al₂O₃、Fe₂O₃、TiO₂、CaO、MgO等6种组分。利用粉末直接压片法制取试样,确定仪器最佳参数,系列标样建立工作曲线,经验系数法对基体效应进行校正。对于主次组分,方法精密度低于5%（n=10）。方法用于实际样品的测定,结果与实验室化学法和其他单位的X射线荧光光谱法相符。方法适用于厂矿企业大批量生产的镁质耐火材料化学组成分析。     

X射线荧光光谱法测定高锶高钡的硅酸盐样品中主量元素

用百分总和检查硅酸盐岩石全分析数据的质量是分析工作者的传统做法,但对于微量元素含量较高的样品,采用X射线荧光光谱法(XRF)进行测定,如果不考虑微量元素的含量及其对主量元素基体效应的影响,往往会使主量元素含量更加偏离真实值。本文针对Sr、Ba含量较高的硅酸盐样品,通过人工配制标准样品,扩大了Sr、Ba校准曲线的定量范围,主量元素校准中加入Sr、Ba的基体校正系数,达到了主量元素定量更加准确可靠的实际效果。采用此方法分析国家标准物质,各主量元素的精密度(RSD)均小于2%;分析不参加回归的标准物质和人工配制的标准样品,主量元素的测量值与标准值(或参考值)基本一致。该方法可以满足硅酸盐的测定要求,主量元素各项结果的加和能够达到《地质矿产实验室测试质量管理规范》的一级标准(99.3%～100.7%)。     

ICP发射光谱法测定硅酸盐岩石中主要元素

本文叙述了电感耦合等离子体原子发射光谱法(ICP-AES)测定硅酸盐岩石中的主要元素的分析方法及结果。我国ICP-AES对痕量分析工作已广泛开展,但在硅酸盐主要元素分析方面如何发挥仪器潜力的报导并不多。本文的目的是提供一个同时测定硅酸盐