Elements Accessible to ICP-IDMS Analysis

Meanwhile, metrological institutions, such as the Institute of Reference Materials and Measurements (IRMM) in Geel, Belgium, and the Bundesanstalt fur Materialforschung und -priifung (BAM) (the Federal Institute for Materials Research and Testing) in Berlin, Germany, distribute certified spike solutions [18, 19], for example, for boron, uranium, plutonium, copper, and zinc. 

If an element has more than two stable isotopes, which is valid for more than 30 elements often measured via IGP-MS, one can select which isotope is to be used as spike and which as reference isotope. It is recommended that the following conditions are fulfilled  

Neither spike nor reference isotope should be subject to spectral overlap due to the occurrence of isobaric nuclides, doubly charged ions, or polyatomic ions. 

Usually the isotope with the lowest natural isotopic abundance is selected as the spike isotope. 

An optimization of the ratio of the amount of spike to the amount of target element in the sample is recommended in IDMS analysis to minimize the error multiplication factor J R), which influences the precision of the result. From Eq. (8.3), it follows that the precision of an IDMS analysis is mainly dependent on the corresponding precision of the spike addition and the isotope ratio (R) measurement, assuming that the uncertainties on the relative isotopic abundances do not contribute significantly for either sample or spike. Under this assumption, the standard deviation s on Ns is described by the following approximation  

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