Fe isotopic analysis by ICP-MS is a real analytical challenge because of the numerous and severe isobaric and polyatomic interferences on the four stable isotopes. In addition to Ar based molecular ions having the same nominal mass-to-charge ratio as the target isotopes (54Fe, 56Fe, 57Fe, and 58Fe) including 40Ar14N, 38Ar16O, 40Ar16O, 38Ar18OH+, 40Ar16OH+, and 40Ar18O+, the presence of high concentrations of concomitant elements in blood samples, such as calcium, can affect the precision and accuracy of Fe isotopic ratios by the formation of 40Ca16O+, 40Ca16OH+, 40Ca18O+, and 42Ca16O+ in the ICP plasma. The presence of Cr and Ni in relatively low concentrations (μg.L−1) in blood samples have also been found to significantly affect the accuracy of ratios involving 54Fe+ and 58Fe+ isotopes. This study combines the techniques of cool plasma and collision/reaction cell to completely eliminate polyatomic interferences and achieve the necessary precision and accuracy in the determination of Fe isotopes to distinguish between male and female whole blood samples.
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