Accurate high throughput quantification of selenium in biological samples – the potential of combining isotope dilution ICP-tandem mass spectrometry with flow injection
In this work, different strategies for the analysis of selenium in human serum were validated by tandem ICP-MS and isotope dilution. The potential of flow injection–ICP-tandem MS was explored to provide accurate quantification of selenium in serum samples, thus allowing high throughputs and low sample consumption (as low as 10 μL) without the requirement of sample preparation. The approach combining on-line isotope dilution and the use of gas modes (either oxygen or hydrogen) is ideally suited to clinical analysis. As a key prerequisite, the 77Se-enriched spike was added on-line to avoid precipitation effects that would occur if samples rich in proteins are mixed with isotopically enriched standards without undergoing previous mineralization procedures. This method proved to be fit for purpose as being validated by using a Serum-Clinchek-certified reference material and by comparing isotope dilution analysis as performed on mineralized samples.