Principles of ICP-IDMS in Elemental Speciation

In contrast to the spedes-specific spiking mode, in the spedes-unspedfic mode the isotope ratio of an elemental species peak varies with time because a constant spike flow is mixed with an elemental spedes of natural isotopic composition. 

An interesting alternative to the more frequentiy applied post olumn spiking mode was developed for FIPLC-ICP-MS by Schaumloffel et al, based on precolumn isotope dilution [69]. In this case, the species-unspecific spike was directly added to the eluents used for separation, which is only possible, of course, if the spike compound does not react with the different analytes and if the column does not fractionate the spike from the analyte, which always needs to be carefully assessed. Successful application of this type of species-unspecific isotope dilution has been demonstrated for the quantification of sulfur ontaining peptides using a 5-labeled sulfate spike. 

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