High-Precision Zinc Isotopic Measurement Of Certified Reference Materials Relevant To The Environmental, Earth, Planetary And Biomedical Sciences

The zinc (Zn) stable isotope system has emerged as a powerful tool for investigating natural and anthropogenic processes of interest to disciplines ranging from the Earth and planetary sciences to biomedical research. In nature, Zn isotopes typically fractionate (Zn-66/Zn-64) within the range of -1 and +1 permil (parts per thousand), and however, analytical limitations restrict the application of the Zn isotope system. Specifically, there is a lack of well-characterised matrix-matched reference materials covering most Zn isotope applications that are essential for validating laboratory performance, particularly given the contamination prone nature of Zn. Furthermore, the increasing demand for analysis of size-limited materials and sample types displaying small, sub-permil level Zn isotope variations requires improvements in measurement procedures. To address these limitations, the delta Zn-66 values of two pure Zn solutions and eighteen reference materials including the previously uncharacterised RGM-2, BCR-279, DOLT-4, DOLT-5, NASS-7, SBC-1, SGR-1b, MESS-3 and HISS-1, and the understudied QLO-1, SDC-1, BCR-414, NASS-6 and COQ-1 materials are reported. Furthermore, a(70)Zn-Zn-67 double-spike design has been implemented that routinely achieves intermediate measurement precision better than +/- 0.02 parts per thousand. This represents at least a two-fold improvement when compared with other double-spike designs, providing a robust platform of delta Zn-66 values required for quality control procedures.