The Istituto di Geoscienze e Georisorse (IGG), on behalf and with the support of the International Atomic Energy Agency (IAEA), prepared eight geological materials (three natural waters and five rocks and minerals), intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials were distributed to twenty seven laboratories ‐ virtually all those performing geochemical boron isotope analyses in the world ‐which agreed to participate in the intercomparison exercise. Only fifteen laboratories, however, ultimately submitted the isotopic and/or concentration results they obtained on the intercomparison materials. The results demonstrate that interlaboratory reproducibility is not well reflected by the precision values reported by the individual laboratories and this observation holds true for both boron concentration and isotopic composition. The reasons for the discrepancies include fractionations due to the chemical matrix of materials, relative shift of the zero position on the δ11B scale and a lack of well characterized materials for calibrating absolute boron content measurements. The intercomparison materials are now available at the IAEA (solid materials) and IGG (waters) for future distribution.

Naturally occurring isotopes of such elements as strontium (Sr) have proved to be good tools for detecting trends in the soil-vegetation system and the tracing of a variety of objects. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has been used for the precise determination of variations in the isotopic composition of Sr. The method described has been applied to the establishment of the potential and limits to determine the geographical origins of different Emmental-type cheese samples. The sample preparation consists of (i) a freeze-drying procedure to remove water, (ii) an extraction step to eliminate the fat components and to obtain the cheese casein fraction, (iii) a thermal decomposition of the latter, and (iv) a chromatographic matrix separation of the redissolved residue. The determination of the isotope abundance ratios 88 Sr/ 86 Sr, 87 Sr/ 86 Sr and 84 Sr/ 86 Sr resulted in precisions of 0.002-0.01%. Simultaneously, the ion currents for krypton ( 83 Kr, 82 Kr) and rubidium ( 85 Rb) were measured to correct for interferences with the Sr isotopes 84, 86 and 87. These and further (argide) spectral interferences causing bias effects to the Sr isotope abundance ratios have been investigated and an adequate computational correction procedure has been assessed. The whole set of validation data has been used for the calculation of the combined standard measurement uncertainty of the isotopic abundance ratio, resulting in a value of 0.016%. Comparison of the measured 87 Sr/ 86 Sr data with thermal ionisation mass spectrometric (TIMS) results, determined on the same cheese samples, agreed within the stated measurement uncertainties, thus indicating that both the validation of the sample preparation procedures and the mass spectrometric measurements cause no evident bias effect with respect to the Sr isotope abundance values. The 87 Sr/ 86 Sr isotope abundance ratios in cheese originating from different regions (alpine, pre-alpine, Bretagne, Finland, Canada, Australia) accorded to local geological properties. No difference was found between ''casein-bound'' and ''whole-cheese'' Sr isotope abundance ratios within the stated measurement uncertainties.

No abstract

No abstract

No abstract