App Note
Interference-free selenium isotope abundance ratio measurements using the Sapphire Collision/Reaction Cell
Selenium has six major isotopes and is an element with main applications in low-temperature geochemistry and biochemistry. Although Se is an important micronutrient, and as such is a critical tracer of metabolic processes, it becomes toxic at high concentrations. Understanding its biological cycling could therefore help in preventing or finding treatments for infectious diseases, cancer, or diabetes because of its anti-inflammatory or antioxidant properties. Due to its various oxidation states, it is also used as a redox tracer to reconstruct the evolution of Earth’s atmosphere and marine environments.
Selenium isotope analysis by MC-ICP-MS is challenging for two reasons: (i) Due to the high ionisation potential of Se the sensitivity is usually low. Cold-vapour hydride generation can overcome this limitation, however stable operation of such systems is difficult. (ii) Plasma-based interferences from ArAr+, ArArH+, and Kr+ affect all Se isotopes, in addition to potential sample-matrix-based interferences from Ge+, AsH+, or BrH+. The use of a Collision/Reaction Cell offers great potential to facilitate Se isotope abundance ratio measurements by eliminating or minimising such isobaric interferences. Here we investigate the use of He-H2 a nd H e-N2 collision/reaction gas mixtures to remove polyatomic and isobaric interferences, enabling the simultaneous quantification of the isotopic abundances of all Se isotopes.
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