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Eingeladener Vortrag
- nein (116)
Triple IDMS has been applied for the first time to the quantification of element concentrations. It has been compared with single and double IDMS obtained on the same sample set in order to evaluate the advantages and disadvantages of triple IDMS over single and double IDMS as an analytical reference procedure. The measurement results of single, double and triple IDMS are indistinguishable, considering rounding due to the individual measurement uncertainties. As expected, the relative expanded uncertainties (k = 2) achieved with double IDMS (0.08 %) are dramatically smaller than those obtained with single IDMS (1.4 %). Triple IDMS yields the smallest relative expanded uncertainties (k = 2, 0.077 %) unfortunately at the expense of a much higher workload. Nevertheless triple IDMS has the huge advantage that the isotope ratio of the spike does not need to be determined. Elements with high memory effects, highly enriched spikes or highest metrological requirements may be typical applications for triple IDMS.
Die Industrie nutzt die Borisotopenanalytik in nukleartechnischen Anwendungen. Umwelt- und Geowissenschaften identifizieren anhand der Borisotopenverhältnisse Kontaminationsquellen und charakterisieren Mischungs- und Fraktionsprozesse. In der Lebensmittelanalytik dient der Parameter dazu, Herkunft und Anbauweise von Obst und Gemüse herauszufinden. Seit kurzem gibt es dafür ein validiertes Verfahren und erste Referenzdaten.
The encyclopedia of mass spectrometry, Volume 5: Elemental and isotope ratio mass spectrometry covers the subject almost entirely and serves as a reference work with links to specialist literature if more details are required.
Therefore, this book can be recommended to all beginners, students, and experts working in this broad field.
IDMS Training
(2016)
Based on its proven records especially in reference material certification, isotope dilution mass spectrometry (IDMS) is considered as one of the most powerful and most accurate methods for determining amounts of substance. Contrary to other calibration approaches, IDMS does not directly suffer from long-time changes or drifts in instrument sensitivity. Moreover, provided isotopic exchange between the sample and spike is ensured, losses of analyte do not affect the analytical result. Both advantages are based on the fact that IDMS only requires isotope ratio measurements and isotope ratios are largely unaffected by instrumental drift, setup or by matrix, unless an isobaric interference is present.
The Consultative Committee for Amount of Substance (CCQM), the world's highest institution for metrology in chemistry, considers IDMS as the most important “Primary Method of Measurement” for amount determination. The total combined uncertainty, according to ISO and EURACHEM guidelines, can easily be calculated via the IDMS equations. Applying it correctly, IDMS has the potential to be a primary method of measurement yielding SI traceable values in the most direct way with combined uncertainties significantly smaller than obtainable by other methods.
In general it can be stated that IDMS is the most important reference method for elemental and elemental species analysis, offering highest accuracy and precision or smallest measurement uncertainties, when properly applied. Thus IDMS represents by far the best suited reference method for RM characterisation. Due to its universal applicability IDMS offers sufficient potential to follow future needs in analytical chemistry as well as in the RM sector.
This presentation will demonstrate the basic principle of IDMS and will show its Pros and Cons as well as its pitfalls. Possible sources of errors and bias are mentioned and correction models will be discussed. Notice will be given to metrological aspects such as traceability and uncertainty. Differences in the application of thermal ionization mass spectrometry and inductively coupled plasma mass spectrometry are discussed as well as differences between different types of mass spectrometers. This will be illustrated by practical examples from various fields.
Isotope analysis
(2017)
The variation of isotope ratios is increasingly used to unravell natural and technical questions. In the past the investigation and interpretation of such variations was the field of a limited number of experts. With new upcoming techniques and research topics in the last decades, such as provenance and authenticity of food, the number of published isotope data strongly increased. Instrumental developments such as the enhancement of inductively coupled plasma mass spectrometers (ICPMS) from an instrument for simple quantitative analysis to highly sophisticated isotope ratio machines influenced this process significantly. While in former times only experts in mass spectrometry were able to produce reliable isotope data, nowadays many laboratories, never been in touch with mass spectrometry before, produce isotope data with an ICPMS. Especially for such user isotope reference materials (IRM) are indispensible to enable a reliable method validation. The fast development and the broad availability of ICPMS also lead to an expansion of the classical research areas and new elements are under Investigation.
This presentation shows the basics and principles for isotope ratio determination using ICP-MS. Additionally, it provides three specific examples for isotope Ratio applications: isotope dilution mass spectrometry; provenancing of archaeoligical artifeacts by lead isotope Ratio Analysis and studies on boron uptake in bell pepper plants.
Absolute Isotope Ratios
(2018)
Measurement results and scientific models leading to important decisions in forensics, food fraud or climatology are based on isotope ratio data. Molar masses of multi-isotopic elements are as well based on isotope ratio data. Thus, in the case of Si, isotope ratios directly impact the redefinition of the SI base units kilogram and mole. Therefore, new strategies are required leading to new primary isotope reference materials, whose isotope ratios are traceable to the SI. This in turn will ensure the comparability of isotope ratio data and will render the traceability exception requested by the CCQM superfluous. Such new procedures will be developed for the key elements S, Si, Ca, Sr and Nd at relative uncertainty levels of ≤ 0.01 %.
This presentation gives a short overview of isotope ratio measurements being carried out in the past few years at BAM in different fields such as plant metabolism, food web structures and archaeology. The corresponding isotope reference materials which have been certified at BAM in parallel are presented as well. Additionally an outlook is being provided on future iRM projects.
Technologie-kritische Elemente (TCE) sind unentbehrliche Materialien für High-Tech Produkte wie Smartphones, Notebooks und Monitors. Ihr Bedarf wird voraussichtlich aufgrund des gesellschaftlichen Wandels hin zu einer grünen Ökonomie exponentiell ansteigen. Dieser Wandel wird vor allem auch durch erneuerbare Energien und Elektromobilität geprägt (European Green Deal). Diese Entwicklung in Verbindung mit einer nahezu fehlenden TCE Produktion in Europa setzt den Markt unter Druck und führt zu steigenden Preisen. Die Sicherung des TCE Nachschubs wurde in der gegenwärtigen Gesundheitskrise noch dringender und wurde daher auch zu einem der Hauptthemen des COVID-19 Recovery Plan, der eine Stärkung der europäischen Resilienz und Autonomie zum Ziel hat. Ein nachhaltige Lösung ist das Recycling der Abfall- bzw. Wertstoffe und letztendlich eine Circular Economy. Allerdings ist die Analyse von Abfallströmen schwierig und erfordert geeignete analytische Lösungen, die SI-rückführbare und somit vergleichbare Messergebnisse im gesamten Recyclingprozess ermöglichen. Die dafür erforderlichen, für TCE zertifizierte, Referenzmaterialien und nötige standardisierte Verfahren fehlen bisher nahezu vollständig. In diesem Beitrag werden die analytischen Herausforderungen, wie z.B. die extreme Heterogenität der Materialien, Schwierigkeiten beim Probenaufschluss und das Fehlen von Referenzmaterialien diskutiert. Und es wird das EMPIR-Projekt MetroCycleEU vorgestellt, dessen Ziel es ist Referenz- und Routineverfahren für ausgewählte TCE (Co, Ga, Ge, In, Ta, Nd, Pr, Dy, Gd, La, Au, Pt, Pd, Rh) zu entwickeln und Referenzmaterialien für Platinen, LEDs und Li-Batterien bereitzustellen.
Technology critical elements (TCE) are key materials for high-tech products such as smartphones, notebooks and monitors. Their demand is expected to increase exponentially due to the shift towards greener economy through the deployment of renewable energy and electro mobility solutions (European Green Deal). This and the lack of TCE production within the EU, puts the market under pressure and leads to increasing prices. The need to secure TCE supply has become even more pressing under the current health crisis and it is a major objective of the Covid-19 Recovery Plan aimed at reinforcing Europe’s resilience and autonomy. A sustainable solution is effective recycling and finally a circular economy. However, the analysis of waste streams is difficult and requires suitable SI traceable analytical solutions to allow for comparability of measurement results throughout the recycling process. The required reference materials (RMs) certified for TCE in the corresponding waste or secondary raw materials and specific documentary standards for TCE to comply with ISO/IEC 17025 requirements, however, are lacking. Furthermore, waste from the so-called “urban mine” is extremely heterogeneous making the estimation of its TCE content difficult. Currently, there is a lack of knowledge at the European level about the TCE stocks and flows in the urban mine. Given the high volume of waste generated and received, fast reliable analytical methods as well as sampling and sample preparation strategies are needed to determine the economic value of the waste and of the final product and to develop and improve recycling procedures.
Within this project we focus on TCEs (Co, Ga, Ge, In, Ta, Nd, Pr, Dy, Gd, La, Au, Pt, Pd, Rh), which have been selected from the list of critical elements for Europe established by the EU in 2020. The overall objective of the project is to provide the reliable and SI traceable determination of TCE in urban waste material at µg/g levels to increase the efficiency and accuracy of TCE recycling. This will be realized by developing validated SI-traceable reference methods, developing traceable and validated RMs for the TCEs, validating the use of the routine methods and RMs for real world applications and facilitating the take up of the technology and measurement infrastructure developed in the project by the measurement supply chain, standards developing organizations and end users.
This presentation will give an overview of the consortium, the project structure and the planned research. First activities will be presented as well.
IRWG strategy update
(2022)
Boron isotope fractionation in soil-plant systems and its influence on biogeochemical cycling
(2022)
Boron (B) is an essential mineral nutrient for higher plants. Although B plant nutrition is well studied, the B isotope fractionation at the soil-plant interface, within plant metabolism, and its influence on biogeochemical cycling is not fully understood. Boron concentrations and isotope variations (δ11B) of the dicotyledonous plants of Chenopodium album and Brassica napus and their growing soils along a climatic gradient were analyzed to decipher these unresolved issues of the B behavior. The boron concentrations and δ11B values show an increasing trend from roots to leaves for both plants, while a decreasing trend from flower to shell and to seed for Brassica napus. A large boron isotope fractionation occurs within the plants with median Δ11Bleaf-root ≈ +20‰, which is related to different boron transporters and transportation ways. Formation of borate dimerized rhamnogalacturonan II in cell and B(OH)3 transportation in xylem lead to heavier δ11B values from root to stem and leaf while B(OH)4 transportation in phloem lead to lighter δ11B values from flower to shell and seed. Although samples cover a distinct transect with systematically different climatic conditions, Δδ11B within the individual plant compartments and between the bulk plants and the soil available B do not show any systematic variation.
This suggests that B uptake from the soil into Chenopodium album and Brassica napus occurs without a distinct isotope fractionation at the soil-plant interface (median Δ11Bbulkplant-soil = 0.2‰) and plants are able to regulate boron uptake. Both the observed large B fractionation within plant and low or absent B isotope fractionation at the soil-plant interface may have profound implications for the biological and geological B cycle. If this observed boron behavior also exists in other plants, their litters would be an important source for exporting 11B-rich biological material from continental ecosystems via rivers to the global oceans. This may be helpful for the explanation of ocean B cycle and the increasing δ11B values over the Cenozoic.
Soil certified reference material (CRM), UME EnvCRM 03 was produced by a collaborative approach among national metrology institutes, designated institutes and university research laboratories within the scope of the EMPIR project: Matrix Reference Materials for Environmental Analysis. This paper presents the sampling and processing methodology, homogeneity, stability, characterization campaign, the assignment of property values and their associated uncertainties in compliance with ISO 17034:2016. The material processing methodology involves blending a natural soil sample with a contaminated soil sample obtained by spiking elemental solutions for 8 elements (Cd, Co, Cu, Hg, Ni, Pb, Sb and Zn) to reach the level of warning risk monitoring values specified for metals and metalloids of soils in Europe. Comparative homogeneity and stability test data were obtained by two different institutes, ensuring the reliability and back up of the data. The certified values and associated expanded uncertainties for the total mass fractions of thirteen elements (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, V and Zn) are established. The developed CRM can be used for the development and validation of measurement procedures for the determination of the total mass fractions of elements in soil and also for quality control/assurance purposes. The developed CRM is the first example of a soil material originating from Türkiye.
ICP-MS has played a key role in inorganic chemical metrology for 25 years, from the 1993 CIPM feasibility study which led to establishment of the CCQM. Since that time, the Inorganic Analysis Working Group of the CCQM has organised 56 international comparisons involving measurements by ICP-MS and, in a recent comparison, 16 different national institutes submitted their results using the technique. Metrological applications of ICP-MS currently address an enormous range of measurements using a wide variety of instrumentation, calibration strategies and methodologies. This review provides an overview of the ICP-MS field with an emphasis on developments which are of particular relevance to chemical metrology.
Examples from CCQM comparisons and the services available from the participants are used to illustrate how the capability and scope of ICP-MS methods have expanded far beyond the expectations of 1993. This is due in part to the research and development Programmes of the national institutes which participate in the CCQM. They have played a key role in advancing new instrumentation and applications for elemental analysis, isotope dilution mass spectrometry, determination of isotopic ratio or composition, and speciation of organometallic compounds. These developments are continuing today, as demonstrated by work in new fields such as heteroatom quantitation of proteins, characterisation and counting of nanoparticles using spICP-MS, and LA-ICP-MS analysis of solid materials.
The performance of second generation ICP-TOFMS, equipped with a micro-channel plate (MCP) enabling multi-isotope detection, in terms of isotope ratio precision and instrumental isotopic fractionation (IIF) for (multi-)isotope ratio analysis was thoroughly assessed for B, Sr and Pb. Experimental isotope ratio precision of 0.14 % for 11B/10B intensity ratio, 0.15 % for 87Sr/86Sr intensity ratio and 0.07% for 208Pb/206Pb intensity ratio were obtained at high signal levels ($500 mg L−1) which is comparable to first generation ICP-TOFMS. The long-term stability of isotope ratios, measured over several hours and expressed as repeatability, is between 0.05 % and 1.8 % for B, Sr and Pb. The observed IIF per mass unit is negative for B (i.e., −11 % for 11B/10B) which is in accordance with measurements using sector field (MC) ICP-MS. But the observed IIF per mass unit is positive for Sr (i.e., 2 % for 87Sr/86Sr) and Pb (i.e., 4.5 % for 208Pb/206Pb) which is not in accordance with measurements using sector field (MC) ICP-MS. Furthermore, different IIFs per mass unit were observed for different isotope pairs of the same isotopic system (i.e., Sr, Pb) and adjacent isotopic systems (i.e., Pb vs. Tl). This and the observations from three-isotope plots for Sr and Pb show that ion formation, ion extraction, ion transmission, ion separation and ion detection in second generation ICP-TOFMS is subject to IIF that does not follow the known mass dependent fractionation laws and is possibly caused by mass independent fractionation and/or multiple (contradictory) fractionation processes with varying contributions. The non-mass dependent IIF behavior observed for second generation ICP TOFMS has profound consequences for the IIF correction of isotope raw data, including application of multi-isotope dilution mass spectrometry (IDMS) using ICP-TOFMS. Hence, only IIF correction models that correct also for mass independent fractionation are applicable to calculate reliable isotope ratios using second generation ICP-TOFMS. In the present study, reliable d11B values, and absolute B, Sr and Pb isotope ratios could be determined using the SSB approach in single-element solutions as well as in a mixture of B, Sr and Pb, where the isotopes were measured simultaneously.
In this study, we demonstrate the applicability of nitrogen microwave inductively coupled atmospheric pressure mass spectrometry (MICAP-MS) for Ca, Fe, and Se quantification in human serum using isotope dilution (ID) analysis. The matrix tolerance of MICAP-MS in Na matrix was investigated, uncovering that high Na levels can suppress the signal intensity. This suppression is likely due to the plasma loading and the space charge effect. Moreover, 40Ca and 44Ca isotopic fractionation was noted at elevated Na concentration. Nine certified serum samples were analyzed using both external calibration and ID analysis. Overestimation of Cr, Zn, As, and Se was found in the results of external calibration, which might be resulted from C-induced polyatomic interference and signal enhancement, respectively. Further investigations performed with methanol showed a similar enhancement effect for Zn, As, and Se, potentially supporting this assumption. The mass concentrations determined with ID analysis show metrological compatibility with the reference values, indicating that MICAP-MS combined with ID analysis can be a promising method for precise Ca, Fe, and Se determination. Moreover, this combination reduces the influences of matrix effects, broadening the applicability of MICAP-MS for samples with complex matrix.
Boron isotope studies on technical materials and geological and environmental samples are one hot topic in nowadays isotope research. Provenance studies of artefacts, food and other products might become another one, as several recent studies demonstrate. Typically boron isotope determinations have been carried out by TIMS. To open up this research field to a broader scientific community we developed two analytical procedures for boron isotope determinations based on single collector SF-ICPMS combined with a sample preparation procedure consisting of dry-ashing and a three step ion chromatographic boron-matrix separation. The developed procedures consist of one low resolution (LR) and one medium resolution (MR) procedure. The repeatability for the δ11B determination in three independently measured aliquots lies between 0.2 and 0.8‰ for the LR procedure and between 0.3 and 1.5‰ for the MR procedure. The expanded uncertainties with a coverage factor of k=2 range between 1.4 and 1.6‰ for the LR procedure and between 2.9 and 3.2‰ for the MR procedure. The accuracy, expressed as average deviation from the reference values, is 0.43‰ for the LR procedure and 0.33‰ for the MR procedure. To test the practicability of the procedures the matrix tolerance has been investigated as well and was found to be up to 2 mg kg-1 of alkaline and alkaline earth elements in the final measurement solution containing 100 µg kg-1 boron. Thus a highly efficient matrix separation for SF-ICPMS boron isotope determinations is required, similar to TIMS.
The aim of this comparison was to demonstrate the capability of national metrology institutes to measure elemental mass fractions at a level of w(E) ≈ 1 g/kg as found in almost all mono-elemental calibration solutions. These calibration solutions represent an important link in traceability systems in inorganic analysis. Virtually all traceable routine measurements are linked to the SI through these calibration solutions. Every participant was provided with three solutions of each of the three selected elements chromium, cobalt and lead. This comparison was a joint activity of the Inorganic Analysis Working Group (IAWG) and the Electrochemical Analysis Working Group (EAWG) of the CCQM and was piloted by the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany) with the help of the Bundesanstalt für Materialforschung und -prüfung (BAM, Berlin, Germany), the Centro Nacional de Metrología (CENAM, Querétaro, Mexico) and the National Institute of Standards and Technology (NIST, Gaithersburg, USA).
A small majority of participants applied inductively coupled plasma optical emission spectrometry (ICP OES) in combination with a variety of calibration strategies (one-point-calibration, bracketing, calibration curve, each with and without an internal standard). But also IDMS techniques were carried out on quadrupole, high resolution and multicollector ICP-MS machines as well as a TIMS machine. Several participants applied titrimetry. FAAS as well as ICP-MS combined with non-IDMS calibration strategies were used by at least one participant. The key comparison reference values (KCRV) were agreed upon during the IAWG/EAWG meeting in November 2011 held in Sydney as the added element content calculated from the gravimetric sample preparation. Accordingly the degrees of equivalence were calculated. Despite the large variety of methods applied no superior method could be identified. The relative deviation of the median of the participants' results from the gravimetric reference value was equal or smaller than 0.1% (with an average of 0.05%) in the case of all three elements.
A thin-layer reference material for surface and near-surface analytical methods was produced and certified. The surface density of the implanted Sb layer was determined by Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA), and inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) equipped with a multi-collector. The isotopic abundances of Sb (121Sb and 123Sb) were determined by multi-collector ICP-MS and INAA. ICP-IDMS measurements are discussed in detail in this paper. All methods produced values traceable to the SI and are accompanied by a complete uncertainty budget. The homogeneity of the material was measured with RBS. From these measurements the standard uncertainty due to possible inhomogeneities was estimated to be less than 0.78% for fractions of the area increments down to 0.75 mm2 in size. Excellent agreement between the results of the three different methods was found. For the surface density of implanted Sb atoms the unweighted mean value of the means of four data sets is 4.8121016 cm-2 with an expanded uncertainty (coverage factor k=2) of 0.0921016 cm-2. For the isotope amount ratio R (121Sb/123Sb) the unweighted mean value of the means of two data sets is 1.435 with an expanded uncertainty (coverage factor k=2) of 0.006.
An ICP-MS equipped with collision cell, sector field and multi-collector technology has been applied to developing analytical procedures for Fe in terms of isotope ratio measurements and isotope dilution analysis. Therefore a detailed study on the reduction of molecular interferences by a variety of collision gases (He, Ar, Kr, H2, D2 and N2) was performed. The efficiency of the reduction has been checked by high resolution mass scans. The argon based interferences disturbing the determination of 54Fe and 56Fe could be completely removed when using Faraday detectors. The interferences on mass 57 could be reduced to a level which enables accurate measurements. Also, the 40Ar12C interference, which disturbs the chromium correction, could be completely removed. Reproducibilities of 0.01% could be reached for 54Fe/56Fe isotope ratios and 0.02% for 57Fe/56Fe isotope ratios. Under these measurement conditions a sensitivity of 1.2 V per 50 µg kg1 Fe is available. This corresponds to 1.5 × 109 cps per mg kg1. Based on these results highly accurate procedures for Fe isotope ratio determinations were set up, reaching a performance level superior to that of other ICP-MS instruments. Consequently, IDMS procedures were developed on this basis in order to perform certification measurements at the highest metrological level. The first application was the contribution to the Fe reference value by IMEP-12, an interlaboratory comparison with approximately 350 participants worldwide. The analysed Fe mass content is 0.2150 mg kg1 with its expanded uncertainty (k= 2) of 0.0012 mg kg1(0.56%), which is ten times less than the uncertainty of the second certification laboratory. Another application was the certification campaign of the two reference materials Tea Leaves and Polish Herbs. The results obtained with the ICP-MS procedure, 542 ± 11 mg kg1 and 543 ± 12 mg kg1, were compared with the results analysed by TIMS, 541 ± 12 mg kg1 and 541 ± 13 mg kg1, and agree very well within the stated uncertainties (k= 2). The results presented demonstrate quite well the suitability of the developed IDMS procedures for certification or reference measurements.
A comparison of different isotope dilution mass spectrometric (IDMS) procedures using inductively coupled plasma mass spectrometry (ICPMS) and thermal ionization mass spectrometry (TIMS) was carried out to examine the degree of equivalence between the used procedures in terms of requirements for reference material certification. The comparison was based on the measurement results and their uncertainties. The sample used in this study is a pure zinc metal to be certified by the Bureau Communie de Référence (BCR) for amount contents of different trace elements. This study focuses on cadmium and thallium. The TIMS values contributed to the certified values. To guarantee identical conditions as far as possible for the procedures under investigation, the samples were split into subsamples after spiking and digestion took place. Thus, every IDMS procedure started with an identical set of samples. In total, four different IDMS procedures and one external calibration procedure using internal standardization as an example of routine analysis were applied. The IDMS procedures divide in a group with and a group without trace/matrix separation. Multicollector TIMS (TI-MC-MS) and multicollector ICPMS (ICP-MC-MS) were used in combination with trace/matrix separation, whereas quadrupole ICPMS (ICP-QMS) and ICP-MC-MS were also applied to nonseparated samples. All IDMS results agree well within their combined uncertainties, while some results from the external calibration procedure do not. IDMS results obtained by ICPMS without separation are comparable to those obtained by TI-MC-MS with separation regarding precision and accuracy. The smallest uncertainties were achieved using ICP-MC-MS in combination with trace/matrix separation.
For the first time, an international comparison was conducted on the determination of the purity of a high purity element. Participants were free to choose any analytical approach appropriate for their institute’s applications and services. The material tested was a high purity zinc, which had earlier been assessed for homogeneity and previously used in CCQM-K72 for the determination of six defined metallic impurities. Either a direct metal assay of the Zn mass fraction was undertaken by EDTA titrimetry, or an indirect approach was used wherein all impurities, or at least the major ones, were determined and their sum subtracted from ideal purity of 100 %, or 1 kg/kg. Impurity assessment techniques included glow discharge mass spectrometry, inductively coupled plasma mass spectrometry and carrier gas hot extraction/combustion analysis. Up to 91 elemental impurities covering metals, non-metals and semi-metals/metalloids were quantified. Due to the lack of internal experience or experimental capabilities, some participants contracted external laboratories for specific analytical tasks, mainly for the analysis of non-metals. The reported purity, expressed as zinc mass fraction in the high purity zinc material, showed excellent agreement for all participants, with a relative standard deviation of 0.011 %. The calculated reference value, w(Zn) = 0.999 873 kg/kg, was assigned an asymmetric combined uncertainty of + 0.000025 kg/kg and – 0.000028 kg/kg. Comparability amongst participating metrology institutes is thus demonstrated for the purity determination of high purity metals which have no particular difficulties with their decomposition / dissolution process when solution-based analytical methods are used, or which do not have specific difficulties when direct analysis approaches are used. Nevertheless, further development is required in terms of uncertainty assessment, quantification of non-metals and the determination of purity of less pure elements and/or for those elements suffering difficulties with the decomposition process.
The major source of the anthropogenic platinum group element (PGE) emission is attributed to the use of catalytic converters in automobiles. This paper describes the work performed by three National Metrology Institutes (Laboratoire national de métrologie et dessais, by the Physikalisch-technische bundesanstalt, Bundesanatalt für materialforschung und prûfung), in the framework of the Joint Research Project 'PartEmission' under the European Metrology Research Program. An analytical procedure based on a cationic exchange protocol and the isotope dilution or standard addition using an Inductived Coupled Plasma Mass Spectrometer, ICP-MS, for the quantification of the elements Pt, Pd and Rh from automotive exhaust emissions is described. Results obtained on a road dust certified reference (BCR 723) material showed a good agreement with the certified values, at ng/g levels, and relative expanded uncertainties within the range of 7–10%. Analysis of filters impacted with automotive exhaust particle emissions (from a diesel engine) showed the amount of collected PGE at levels of 10–1000 pg/filter. Their quantifications followed the developed analytical protocol that had been carried out with relative expanded uncertainties in the range of a few per cent up to 20% per filter. Nevertheless, a lack of homogeneity between the filters was observed, making the comparison between the project partners difficult in the sake of the validation of their analytical procedures on real samples.
A two-step separation procedure for the quantification of Pd and Pt in automotive exhaust emissions using isotope dilution mass spectrometry was established using a combination of cation and anion exchange chemistry. AG 50W-X12 was used as cation exchange resin and DGA as weakly basic anion exchange resin. This procedure enabled the effective separation of Pd and Pt from the matrix and from interfering elements. Additionally Pd and Pt were collected in separate chromatographic fractions, which increased the precision of the isotope ratio determination by separate measurements using single collector sector field ICPMS. The analytical procedure was validated by analysing the synthetically prepared samples and the certified reference materials BCR-723 (road dust) and IAEA-450 (algae). For the SI-traceable results complete uncertainty budgets were calculated yielding relatively expanded uncertainties (k = 2) of ≈1% for analyte masses in the ng range. Procedure blanks of 55 pg Pd and 3 pg Pt were obtained. The detection limits were calculated as 12 pg for Pd and 7 pg for Pt. Additionally, Pd and Pt blank levels of different filter materials are presented as well as the first results for automotive exhaust particles collected on cellulose filters.
Within the National Metrology Institutes (NMIs) and designated laboratories, an interlaboratory comparison, CCQM-P107, was conducted to verify the degree of international comparability concerning the results of purity analysis. The mass fractions of Ag, Bi, Cd, Cr, Ni, Tl at the lower mg/kg-level in a high purity zinc material were determined, but the real measurand in metrological sense was the sum of the six mass fractions. Homogeneity was investigated by glow discharge mass spectrometry, reference values were obtained using isotope dilution mass spectrometry. Six NMIs participated, contributing eight independent data sets. The agreement amongst the results of the participants, their median and the agreement with the reference values were usually excellent and in almost all cases below the target uncertainty of 30% relative. In this manner, the accuracy of results and the comparability between the participants was demonstrated to be established.
Isotope amount ratios (hereafter referred to as simply isotope ratios) are proving useful in an ever increasing array of applications that range from studies unravelling transport processes, to pinpointing the provenance of specific samples as well as trace element quantification by using isotope dilution mass spectrometry (IDMS). These expanding applications encompass fields as diverse as archaeology, food chemistry, forensic science, geochemistry, medicine and metrology. However, to be effective tools, the isotope ratio data must be reliable and traceable to enable the comparability of measurement.
The importance of traceability and comparability in isotope ratio analysis has already been recognized by the Inorganic Analysis Working Group (IAWG) within the CCQM. Three pilot studies have focused on the quality of isotope ratio determinations (P48 “U isotope ratios in urine”, P75 “stable isotopes in Methionine”, P105 “87Sr/86Sr in wine”). Moreover, isotope ratio measurements are fundamental to IDMS amount of substance determinations. For example, when Pb quantification using IDMS is undertaken, this requires the measurements of Pb isotope ratios. While the requirements for isotope ratio accuracy and precision in the case of of IDMS are generally quite modest, “absolute” Pb isotope ratio measurements for geochemical age dating and source rock characterization as well as forensic provenance and fingerprinting studies require Pb isotope ratio measurements of the highest quality. To support present and future CMCs on isotope ratio determinations, a Key Comparison was urgently needed. Therefore, it was decided at the IAWG meeting in Paris in April 2011 that a Key Comparison on the determination of Pb isotope ratios in a pure Pb solution and in a bronze sample should be organized and accompanied by a pilot study.
Measuring Pb isotope amount ratios in a pure Pb solution, while seemingly straight forward, rigorously tests the ability of analyst to correct for any instrumental effects (such as mass discrimination and blank correction) on the measured ratios. Pb, present in trace amounts in a metal matrix sample (e.g. Pb in bronze), provides a real world test of the whole chemical and instrumental procedure, from chemical separation and sample purification to analysis and subsequent correction of appropriate instrumental effects on the separated samples.
A suitable bronze material with a Pb mass fraction between 10 and 100 mg·kg-1 was available at BAM. A high purity solution of Pb with a mass fraction of approximately 100 mg·kg-1 was also available. By comparing the Pb isotope ratio results obtained for the bronze sample with the Pb isotope ratio results from the Pb solution, potential biases arising from the processing of the bronze sample could be effectively identified and separated from the instrumental effects arising from the measurement and data processing protocol.
Various plant compartments of a single bell pepper plant were studied to verify the variability of boron isotope composition in plants and to identify possible intra-plant isotope fractionation. Boron mass fractions varied from 9.8 mg/kg in the fruits to 70.0 mg/kg in the leaves. Boron (B) isotope ratios reported as δ11B ranged from -11.0 to +16.0 (U ≤ 1.9, k=2) and showed a distinct trend to heavier δ11B values the higher the plant compartments were located in the plant. A fractionation of Δ11Bleaf-roots = 27 existed in the studied bell pepper plant, which represents about about 1/3 of the overall natural boron isotope variation (ca. 80). Two simultaneous operating processes are a possible explanation for the observed systematic intra-plant δ11B variation: 1) B is fixed in cell walls in its tetrahedral form (borate), which preferentially incorporates the light B isotope and the remaining xylem sap gets enriched in the heavy B isotope and 2) certain transporter preferentially transport the trigonal 11B-enriched boric acid molecule and thereby the heavy 11B towards young plant compartments which were situated distal of the roots and typically high in the plant. Consequently, an enrichment of the heavy 11B isotope in the upper young plant parts located at the top of the plant could explain the observed isotope systematic. The identification and understanding of the processes generating systematic intra-plant δ11B variations will potentially enable the use of B isotope for plant metabolism studies.
We report an appropriate preparation of binary isotope calibration mixtures of the three stable isotopes of magnesium to be used in the ab initio calibration of multicollector mass spectrometers (ICPMS and TIMS). For each of the three possible combinations of binary mixtures ("24Mg" + "25Mg", "24Mg" + "26Mg", and "25Mg" + "26Mg"), three individual setups have been prepared under gravimetric control, each of them with an isotope ratio close to unity, and a total magnesium mass fraction close to 20 mg kg-1. The preparation was designed to occur via an intermediate dilution of a parent solution of a highly purified specimen of the isotopically enriched magnesium materials. For the application as calibration mixtures, a complete uncertainty budget was set up, and is presented and discussed in detail, including the aspects that went into the design of the dilution and mixing approach to minimize uncertainty. The principle parameters for the purpose of the later calibration of the mass spectrometers are the absolute masses of isotopically enriched magnesium materials in the primary calibration mixtures. For the first time relative expanded uncertainties U (k = 2) for these masses of ≤0.005% could be achieved for all mixtures.
Three petrol reference materials were certified for their total sulfur content in support of Directive 2003/17/EC of the European Parliament and of the European Council, which stipulates that petrol with a maximum S content of 10 mg/kg must be available in all member states by 2009. Commercially available petrol was obtained and filled into borosilicate ampoules without further treatment. Homogeneity of the materials was tested and no heterogeneity was detected for two of the materials, whereas minor heterogeneity was observed for the third material. Stability of the materials was tested for 8-12 months at 60 °C and no degradation was observed. Characterisation was based on isotope-dilution mass spectrometry (IDMS) applied as primary method of measurement by three European metrology institutes and certified values were assigned using all results. The certified uncertainties include contributions of (potential) heterogeneity, potential degradation as well as characterisation. The final assigned values are:
ERM-EF211: 48.8 ± 1.7 mg/kg
ERM-EF212: 20.2 ± 1.1 mg/kg
ERM-EF213: 9.1 ± 0.8 mg/kg
The materials are available from IRMM (ERM-EF211), LGC (ERM-EF212) and BAM (ERMEF213)
Isotope dilution mass spectrometry often is applied for the quantification of platinum group elements in environmental and geological samples. In most cases, however, certified spike solutions offering complete uncertainty statements and SI-traceability are missing. This report describes the production and certification of two isotope reference materials, ERM-AE140 and ERM-AE141, serving as calibrated spike solutions for IDMS based quantification of Pd and Pt, respectively. Both materials were produced by dissolving highly enriched isotopes 106Pd and 194Pt and determining the mass fraction of 106Pd and 194Pt in the final solution by reverse IDMS. Two independent back-spikes were produced for each material from high purity Pd and Pt. Characterization measurements were carried out by MC-ICPMS. For ERM-AE140 the certified mass fractions are w(106Pd) = 20.24(5) mg/kg and w(Pd) = 20.54(5) mg/kg. For ERM-AE141 the certified mass fractions are w(194Pt) = 18.18(11) mg/kg and w(Pt) = 19.90(12) mg/kg. These values are traceable to the International System of Units (SI) in the shortest possible way.
Certification report for the reference materials ERM-AE102a, -AE104a, -AE120, -AE121 and -AE122
(2010)
Isotope reference materials are essential to enable reliable and comparable isotope data. Besides the correction of mass fractionation or mass discrimination isotope reference materials are indispensible for validation and quality control of analytical procedures. This article describes the production and certification of a set of five isotope reference materials ERM-AE102a, 104a, AE120, 121 and 122, for boron isotope analysis. The isotopic composition of all materials has been adjusted by mixing boron mother solutions enriched in 10B or 11B with a boron mother solution having natural-like isotopic composition under full gravimetric control. All mother solutions have been analysed for their boron mass fraction as well as their boron isotopic composition by TIMS using IDMS as calibration technique. For all five reference materials the isotopic composition obtained on the basis of the gravimetric data agrees very well with the isotopic composition obtained from different TIMS techniques. Performed stability and homogeneity studies show no significant influence on the isotopic composition as well as on the related uncertainties.
The certified isotope abundances for 10B are 0.29995 (27) for ERM-AE102a and 0.31488 (28) for ERM-AE104a. The certified δ11B values are -20.2 (6) ‰ for ERM-AE120, 19.9(6) ‰ for ERM-AE121 and 39.7 (6) ‰ for ERM-AE122.
Together with the formerly certified ERM-AE101 and -AE103 a unique set of seven certified reference materials (CRM) for boron isotope analysis is now available from BAM.
Dieser Bericht beschreibt die Zertifizierung von 3 synthetischen Isotopenmischungen aus natürlicher und angereicherter Borsäure. Diese Isotopen-ZRM liegen als konzentrierte, wäs-serige Borsäure-Lösungen vor und sind bezüglich ihrer Isotopenzusammensetzung zertifi¬ziert. Der Bor-Gesamtgehalt ist als Richtwert angegeben. Die Unsicherheiten sind erweiterte Messunsicherheiten mit k=2. Sie sind in Klammern angegeben und beziehen sich auf die letzten beiden Stellen. Die vorliegenden Isotopen-ZRM sind bezüglich ihrer Isotopenzu¬sam-mensetzung mit erweiterten relativen Messunsicherheiten kleiner 0,12% zertifiziert. Die ab-solute, kombinierte Standardunsicherheit des prozentualen Stoffmengenanteils der Isotope (Isotopenhäufigkeit) liegt zwischen 0.012 und 0.017.
Previously applied methods for the quantification of sulphur in copper and other pure metals revealed a lack of SI-traceability and additionally showed inconsistent results, when different methods were compared.
Therefore, a reference procedure is required which allows SI-traceable values accompanied by a Sound uncertainty budget. In this study a procedure was developed for the quantification of total sulphur in copper at low concentration levels using inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS). The major part of the copper matrix was separated by adding ammonia which forms a complex with the copper while releasing the sulphur followed by chromatographic separation using a weak cation resin. After that the sulphur fraction was further purified by chromatographic means using first an anion exchange method and second a chelating resin. The developed procedure shows high performance, especially concerning high efficiency in matrix removal (>99.999%) while keeping the recovery of sulphur above 80%. Procedure blanks are in the order of 3–53 ng resulting in LOD and LOQ values of 0.2 mg g1 and 0.54 mg g1, respectively. The procedure is sufficient to facilitate value assignment of the total sulphur mass fraction in reference materials. Additionally, relative measurement uncertainties were calculated to be below 1% and the measurement results were traceable to the SI. The procedure reported in this study is a new reference procedure for sulphur measurement in copper, being fit for two major purposes, certification of reference materials and assignment of reference values for inter-laboratory comparison.
An alternative method for lithium isotope amount ratio analysis based on a combination of high-resolution atomic absorption spectrometry and spectral data analysis by machine learning (ML) is proposed herein. It is based on the well-known isotope shift of approximately 15 pm for the electronic transition 22P←22S at around the wavelength of 670.8 nm, which can be measured by the state-of-the-art high-resolution continuum source graphite furnace atomic absorption spectrometry. For isotope amount ratio analysis, a scalable tree boosting ML algorithm (XGBoost) was employed and calibrated using a set of samples with 6Li isotope amount fractions, ranging from 0.06 to 0.99 mol mol–1, previously determined by a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). The calibration ML model was validated with two certified reference materials (LSVEC and IRMM-016). The procedure was applied toward the isotope amount ratio determination of a set of stock chemicals (Li2CO3, LiNO3, LiCl, and LiOH) and a BAM candidate reference material NMC111 (LiNi1/3Mn1/3Co1/3O2), a Li-battery cathode material. The results of these determinations were compared with those obtained by MC-ICP-MS and found to be metrologically comparable and compatible. The residual bias was −1.8‰, and the precision obtained ranged from 1.9 to 6.2‰. This precision was sufficient to resolve naturally occurring variations, as demonstrated for samples ranging from approximately −3 to +15‰. To assess its suitability to technical applications, the NMC111 cathode candidate reference material was analyzed using high-resolution continuum source atomic absorption spectrometry with and without matrix purification. The results obtained were metrologically compatible with each other.
The therapeutic dose of lithium (Li) compounds, which are widely used for the treatment of psychiatric and hematologic disorders, is close to its toxic level; therefore, drug monitoring protocols are mandatory. Herein, we propose a fast, simple, and low-cost analytical procedure for the traceable determination of Li concentration in human serum, based on the monitoring of the Li isotope dilution through the partially resolved isotope shift in its electronic transition around 670.80 nm using a commercially available high-resolution continuum source graphite furnace atomic absorption spectrometer. With this technique, serum samples only require acidic digestion before analysis. The procedure requires three measurements—an enriched 6Li spike, a mixture of a certified standard solution and spike, and a mixture of the sample and spike with a nominal 7Li/6Li ratio of 0.82. Lanthanum has been used as an internal spectral standard for wavelength correction. The spectra are described as the linear superposition of the contributions of the respective isotopes, each consisting of a spin-orbit doublet, which can be expressed as Gaussian components with constant spectral position and width and different relative intensity, reflecting the isotope ratio in the sample. Both the spectral constants and the correlation between isotope ratio and relative band intensity have been experimentally obtained using commercially available materials enriched with Li isotopes. The Li characteristic mass (mc) obtained corresponds to 0.6 pg. The procedure has been validated using five human serum certified reference materials. The results are metrologically comparable and compatible to the certified values. The measurement uncertainties are comparable to those obtained by the more complex and expensive technique, isotope dilution mass spectrometry.
Polyethylene (PE) frits were used to quantify sulphur in copper and its alloys by isotope dilution combined with LA-ICP-MS as an alternative approach to conventional sample preparation: the copper samples were spiked, the spiked samples were dissolved, the resulting solutions were absorbed in the PE frits and finally the PE frits were analysed by LA-ICP-MS. A prerequisite for such a support material is a low sulphur blank and thus PE was selected for this purpose. The absorption efficiency of the PE frits was studied for varying sulphur amounts ranging from 2 mg S to 80 mg S showing that more than 99.5% of the loaded sulphur was absorbed by the frit. The so prepared PE frits were measured by LA-ICP-MS and yielded a good linearity (R2 ¼ 0.999) for the sulphur ion intensities corresponding to sulphur amounts up to 40 mg S; the associated sensitivity is approximately 3.4 x 10⁴ cps μg⁻¹ for ³²S. For the validation of the developed procedure the reference materials BAM-M376a, BAM-228 and BAM-227 were applied such that 2 μg S, 5 μg S and 11 μg S were absorbed in the PE frits, respectively. These samples were pre-quantified for the adsorbed sulphur amount by external calibration LA-ICP-MS yielding sulphur amounts of 0.9 μg, 5.1 μg and 8.5 μg (quantified for ³²S only), respectively. Relative Standard deviations of the isotope ratios were below 5% in average (n ¼ 3 lines) in all cases (except for the pure spike solution). These samples were then analysed by LA-ICP-IDMS and the measurement results were validated by comparing them with the results obtained by conventional ICP-IDMS. The obtained relative expanded measurement uncertainties ranged between 10% and 26%. Pearson's coefficient was used to express the correlation between both techniques; the obtained value was 0.999 demonstrating a strong correlation. Contrary to most published LA-ICP-IDMS procedures, the developed procedure enables SI-traceability for the measurement results. The metrological traceability to the SI for the sulphur mass fractions in copper was established by an unbroken chain of comparisons, each accompanied by an uncertainty budget. Thus, the measurement results are considered reliable, acceptable and comparable within the stated measurement uncertainty. The metrological traceability chain from the kg down to mass fraction in the samples obtained by LA-ICP-IDMS is presented as well.
Boron isotope amount ratios n(10B)/n(11B) have been determined by monitoring the absorption spectrum of boron monohydride (BH) in a graphite furnace using high-resolution continuum source molecular absorption spectrometry (HR-CS-MAS). Bands (0→0) and (1→1) for the electronic transition X1Σ+ → A1Π were evaluated around wavelengths 433.1 nm and 437.1 nm respectively. Clean and free of memory effect molecular spectra of BH were recorded. In order to eliminate the memory effect of boron, a combination of 2% (v/v) hydrogen gas in argon and 1% trifluoromethane in argon, an acid solution of calcium chloride and mannitol as chemical modifiers was used. Partial least square regression (PLS) for analysis of samples and reference materials were applied. For this, a spectral library with different isotopes ratios for PLS regression was built. Results obtained around the 433.1 nm and 437.1 nm spectral regions are metrologically compatible with those reported by mass spectrometric methods. Moreover, for the evaluated region of 437 nm, an accuracy of 0.15‰ is obtained as the average deviation from the isotope reference materials. Expanded uncertainties with a coverage factor of k = 2 range between 0.15 and 0.44‰. This accuracy and precision are compatible with those obtained by mass spectrometry for boron isotope ratio measurements.
The quantification of the sulphur mass fraction in pure copper and copper alloys by GDMS and LA-ICP-MS revealed a lack of traceability mainly due to a lack of suitable certified reference materials for calibrating the instruments. Within this study GDMS and LA-ICP-MS were applied as routine analytical tools to quantify sulphur in copper samples by applying reference materials as calibrators, which were characterized for their sulphur mass fraction by IDMS beforehand. Different external calibration strategies were applied including a matrix cross type calibration. Both techniques with all calibration strategies were validated by using certified reference materials (others than those used for calibration) and good agreement with the reference values was achieved except for the matrix cross type calibration, for which the agreement was slightly worse. All measurement results were accompanied by an uncertainty statement. For GDMS, the relative expanded (k = 2) measurement uncertainty ranged from 3% to 7%, while for LA-ICP-MS it ranged from 11% to 33% when applying matrix-matched calibration in the sulphur mass fraction range between 25 mg kg-1 and 1300 mg kg-1. For cross-type calibration the relative expanded (k = 2) measurement uncertainty need to be increased to at least 12% for GDMS and to at least 54% for LA-ICP-MS to yield metrological compatibility with the reference values. The so obtained measurement results are traceable to the international system of units (SI) via IDMS reference values, which is clearly illustrated by the unbroken chain of calibrations in the metrological traceability scheme.
In this study, an analytical procedure for multi-element screening of 40 elements in milk and feed samples was developed. Three different digestion and two different calibration methods were tested for the best suitability. The analytical procedure for the quantification of minor and trace elements is based on sector field ICP-MS (SF-ICP-MS). The method validation revealed good agreement between the determined elemental mass fractions and the certified values of two milk and three feed reference materials. Milk samples of dairy cows at different feeding regimes were collected from two different farms. The results of our study showed significant differences of nine elemental mass fractions (Li, P, Mn, Co, Cu, Rb, Sr, Br, I) between milk from the two locations. Further, a correlation between the elemental mass fractions of milk and the ingested feed and water was observed.
The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The δ13C values of milk and urine were dependent on different feeding regimes based on C3 or C4 plants. The δ13C values are more negative under grass feeding than under maize feeding. The δ13C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed milk and urine samples are enriched in 13C relative to the feed, whereas under maize feeding the 13C/12C ratio of urine is in the same range and milk is depleted in 13C relative to the diet. The difference between the 15N/14N ratios for the two feeding regimes is less pronounced than the 13C/12C ratios. The δ15N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences between the two feeding regimes.
In the interest of exploring their potential in the field of single particle analysis, a Microdroplet Generator (MDG) was coupled to an ICP-ToF-MS. Isotopic Dilution Analysis was also incorporated for the size determination of three different Platinum nanoparticles samples (50, 63 and 70 nm). The performance of the technique was validated by comparison to traditional size characterization techniques (sp-ICP-ToF-MS, TEM), while the robustness of the technique was proven by incorporating NaCl in the samples’ matrix, up to 100 mg/L.
This presentation provides a short introduction to the Commission on Isotopic Abundances and Atomic Weights (CIAAW). It describes the role of the Commission and provides an insight into its work and the corresponding principal tasks. Finally, it provides the reader with the latest achievements and with the most recent publications.