Absolute isotope ratios – Analytical solution for the determination of calibration factors for any number of isotopes and isotopologues

Absolute isotope ratios of carbon dioxide – a feasibility study

“…Since 13 C + / 12 C + can be measured directly, the calculation of the K-factor (and its associated uncertainty) can be simplied tremendouslyuseful tools were published. 31,42 Also no assumptions for the 17 O corrections are needed. Furthermore, with the latest advances in the eld of high resolution ICP-MS and 10 13 U amplier resistors maybe it is even possible to measure also 18 O + / 16 O + .…”

“…A comprehensive explanation of this method can be found in the ESI, † or the literature. 31,42 If we adapt this approach to carbon dioxide with its twelve isotopologues, see Table 1, four obstacles may be encountered. First, to straightforwardly adapt the described procedure, it would be necessary to measure all twelve isotopologues at once.…”

“…In this simulation, it is assumed that there is a mass spectrometer that is capable of detecting and resolving all twelve isotopologues at once. In a previous publication, 31 we already used this made-up data set for demonstrating how Kfactors can be calculated for a system with more than four isotopes, but we neglected the inuence of isotope equilibrium. All of the mathematics behind this simulation can be traced using the mentioned EXCEL® le and the given formulas.…”

“…These biased intensity ratios were then entered into our tool called GIMiCK. 31 Since the initial set of K-factors is known, the comparison of the initial set and the set obtained from the new isotopologue ratios is a good way of investigating, whether scrambling inuences the calculation. In Table 2 the initial and the new sets are compared.…”

“…With the knowledge of the masses of the parent materials and the measured ion intensities, the needed K-factors can be calculated. 30,31 The procedure is explained briey later in ESI † accompanying this publication. This method has been successfully used to obtain absolute isotope ratios, for example, in the Avogadro project 32 in order to determine the molar mass of a 28 Si enriched sphere and to develop new potential isotope reference materials for magnesium.…”