TY - GEN A1 - Vogl, Jochen T1 - Isotope ratios and delta values with minimal measurement uncertainties -measuring magnesium using MC-ICP-MS N2 - Multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) has evolved significantly since its introduction in 1992. The second and third generation instruments now allow isotope ratio measurements at unprecedented precisions, 0.001 % or better. However, precision alone is not enough for producing accurate and reliable isotope ratio measurements. Metrological considerations such as the selection of suitable calibration strategies, proper assessment of instrumental biases, and the estimation of overall measurement uncertainty remain critical to the measurement process. Properly assessed, measurement uncertainty then provides the interval within which a result can be considered both accurate and precise. All mass spectrometric measurements are affected by instrumental mass discrimination and produce isotope ratios that are biased relative to their “true” ratio. To produce accurate and traceable isotope ratio measurements, it is imperative that certified isotope reference materials (iCRMs) be used for calibration and validation purposes. iCRMs reporting absolute isotope ratios are an analyst’s first choice, particularly when its uncertainty is sufficient for the intended use. However, when smaller uncertainties are required to resolve subtle differences between samples, delta-scale measurements become important. Here, the difference between an isotope ratio measured in a sample and in an internationally accepted isotope reference material (iRM) is determined. This deviation can be positive or negative relative to the iRM, is called a delta value, and is often expressed in per mil units. This presentation will highlight the potential for MC-ICP-MS to produce isotope ratio measurements with minimal uncertainties by examining three applications involving Mg isotopes: 1) the certification of a set of iCRMs for their absolute isotope ratio using a gravimetric isotope mixture approach; 2) the comparison of these iCRMs with currently accepted Mg delta-scale reference materials through intercalibration, and 3) the determination of isotope fractionation exponents for geochemical applications. T2 - 4th International Conference on Frontiers in Mass Spectrometry CY - Kottayam, Kerala, India DA - 04.12.2019 KW - Triple isotope fractionation KW - Absolute isotope ratio KW - Delta value KW - Mangesium PY - 2019 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/50004 AN - OPUS4-50004 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany