Development of Two New Copper Isotope Standard Solutions and their Copper Isotopic Compositions

In this study, two new laboratory reference solutions for testing Cu isotopic composition were established and investigated. Two commercially available pure copper products, copper plate and copper wire, were dissolved in 1000-ml Teflon® bottles, to produce 200 μg ml−1 stock solutions (hereafter referred to as NWU-Cu-A and NWU-Cu-B), and cryogenically stored. The Cu isotopic compositions of the two samples were determined in three different laboratories using multi-collector inductively coupled plasma-mass spectrometry, and the Cu isotopic compositions obtained from the standard-sample bracketing method were consistent within the two standard deviation (2s) range. The Cu isotopic compositions of the NWU-Cu-A and NWU-Cu-B standard solutions were δ65Cu = +0.91 ± 0.03‰ (2s, n = 42) and δ65Cu = −0.05 ±0.03‰ (2s, n = 49), respectively, relative to the reference material NIST SRM 976.