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.
Three new offset Delta11B isotope reference materials for environmental boron isotope studies
(2011)
The isotopic composition of boron is a well established tool in various areas of Science and industry. Boron isotope compositions are typically reported as 5nB values which indicate the isotopic difference of a sample relative to the isotope reference material NIST SRM 951.
A significant drawback of all of the available boron isotope reference materials is that none of them covers a natural boron isotope composition apart from NIST SRM 951. To fill this gap of required 5UB reference materials three new solution boric acid reference materials were produced, which cover 6096o of the natural boron isotope Variation (-20 to 40%oo B) of about 100%o. The new reference materials are certified for their B values and are commercially available through European Reference Materials® (http://wwrv.enn-cmi.org). The newly produced and certified boron isotope reference materials will allow straightforward method Validation and quality control of boron isotope data.
Development and validation of a method to determine the boron isotopic composition of crop plants
(2011)
We present a comprehensive chemical and mass spectrometric method to determine boron isotopic compositions of plant tissue. The method including dry ashing, a three-step ion chromatographic boron–matrix separation, and 11B/10B isotope ratio determinations using the Cs2BO2+ graphite technique has been validated using certified reference and quality control materials. The developed method is capable to determine δ11B values in plant tissue down to boron concentrations of 1 mg/kg with an expanded uncertainty of ≤1.7‰ (k = 2). The determined δ11B values reveal an enormous isotopic range of boron in plant tissues covering three-quarters of the natural terrestrial occurring variation in the boron isotopic composition. As the local environment and anthropogenic activity mainly control the boron intake of plants, the boron isotopic composition of plants can be used for food provenance studies.