Requirements for Isotopic Reference Materials

The terms RM, CRM, and IRM have already been defined in Section 6.1. These internationally accepted definitions clearly make two important statements the differentiation between RMs and CRMs and the definition of the basic requirements thereof For an isotopic reference material, the requirements are as follows  

These are rather general requirements and need to be specified further (see below). Isotope amount ratios are used for different applications, such as the determination of elemental contents, determination of isotopic variations for the interpretation of specific incidents and processes in bio- or geochemistry, and characterization of materials. Interference corrections are also based on isotope amount ratios calculated from the lUPAC-tabulated isotope amount fractions [57]. 

In elemental analysis by ICP-MS, a difference in the isotopic composition between the sample and the calibration standard leads to a bias in the measurement result, that is, the elemental content determined. In serious routine analysis, the isotopic variation of certain elements therefore needs to be considered. For lead determination, often the ion currents of the isotopes ° Pb, Pb, and Pb are summed and this sum is used for the calculations, because the sum of all isotope amount fractions is one and therefore is not susceptible to isotopic variations. However, two approximations are included first, the ion current of Pb is not used owing to its low isotope amount fractions and the interference from 

Element Isotope Description State Composition Code  

Iodine 129j High level Solution Alkaline NIST SRM 3231 

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