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Eingeladener Vortrag
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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.
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.
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.
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.