Abstract

Zinc is an essential element to humans, and accurate measurements of zinc isotope ratios and total zinc content in metabolic studies are therefore crucial. In the present study a new method is described for the simultaneous measurement of zinc isotope ratios (⁶⁴Zn⁺/⁶⁶Zn⁺, ⁶⁷Zn⁺/⁶⁶Zn⁺, ⁶⁸Zn⁺/⁶⁶Zn⁺ and ⁷⁰Zn⁺/⁶⁶Zn⁺) and total zinc content in human faeces, urine and serum using high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). Relative standard deviations (RSD) of 0.7% were found for ⁶⁷Zn⁺/⁶⁶Zn⁺, ⁶⁸Zn⁺/⁶⁶Zn⁺ and ⁷⁰Zn⁺/⁶⁶Zn⁺, while a RSD of 1.2% was found for ⁶⁴Zn⁺/⁶⁶Zn⁺. Judged by the analysis of faecal sample solutions spiked with enriched ⁶⁸Zn the accuracy of the isotope ratio measurements is high. The measurement of total zinc content showed a fairly good agreement with atomic absorption spectrometry (AAS) data. Using a mass resolution of 6000 all zinc isotopes could be measured free from interferences, except for ⁶⁴Zn⁺, where the overlap from ⁶⁴Ni⁺ had to be corrected for mathematically. The use of different mass resolution settings ensured a positive identification of all spectral interferences found on the zinc isotopes in faeces, urine and serum.