An improved method of Cr purification for high precision measurement of Cr isotopes by double spike MC-ICP-MS

Abstract

A flexible, easy and highly efficient Cr purification method was developed for high-precision measurement of Cr isotopes by double-spike MC-ICP-MS.

High‐Precision Measurement of Stable Cr Isotopes in Geological Reference Materials by a Double‐Spike TIMS Method

“…In this study, two basalt reference materials from the USGS, BHVO‐1 (−0.120 ± 0.029‰, 2 s ) and BHVO‐2 (−0.129 ± 0.032‰, 2 s ), gave slightly lower δ 53/52 Cr NIST SRM 979 values than that of peridotite reference material JP‐1 from JSG (−0.088 ± 0.034‰; 2 s ) with the mean results over a period of two years. The data obtained in this study for these basalt and peridotite reference materials are consistent with the δ 53/52 Cr NIST SRM 979 values reported by previous studies within the precision quoted (Schoenberg et al , , Wang et al , Li et al , , Gueguen et al , Bonnand et al , b, Wu et al , Xia et al , Zhu et al ) (Figure b).…”

“…Comparison of geological reference material data analysed in this study (red symbols) with literature values (black symbols) (Schoenberg et al , , Gueguen et al . , Wang et al , Li et al , , Bonnand et al , b, Xia et al , Wu et al , Zhu et al ). [Colour figure can be viewed at wileyonlinelibrary.com]…”

“…The 50 Cr‐ 54 Cr double spike is usually used to correct the mass dependence fractionation generated during sample processing as well as by instrumental mass bias effects for the Cr isotope ratio of samples (Ellis and Bullen , Schoenberg et al , Frei et al , Zink et al , Qin et al , Bonnand et al , Farkaš et al , Planavsky et al , Wang et al , Cole et al , Li et al , Xia et al , Zhu et al ). The mass‐dependent isotopic fractionation in the laboratory, from the column chemistry and from isotopic fractionation by TIMS, was corrected by a 50 Cr‐ 54 Cr double‐spike technique.…”

“…Chromium mainly has two valence states in solution, and the behaviours of Cr(III) and Cr(VI) during ion exchange separation are very different (Schoenberg et al , Trinquier et al , Yamakawa et al , Li et al ). To convert all chromium ions to the same valence state, various oxidising or reducing agents ((NH 4 ) 2 S 2 O 8 , K 2 S 2 O 8 , KMnO 4 and HCl) were used in previous studies in the anion or cation resin stage, and correspondingly, two, three or even four columns were used (Table ; Lugmair and Shukolyukov , Ball and Bassett , Ellis and Bullen , Johnson and Bullen , Halicz et al , Trinquier et al , Schoenberg et al , Yamakawa et al , Døssing et al , Schiller et al , Rodler et al , Li et al , Schoenberg et al , Li et al , Zhu et al ). These methods can obtain satisfactory pure Cr cuts from multiple kinds of samples.…”

Factors affecting chromium isotope measurements using the double‐spike method

“…Later, Ellis et al added a 50 Cr‐ 54 Cr double spike to the sample to correct for mass‐dependent fractionation during both the TIMS measurement and the purification process; these authors obtained an external precision of ±0.2‰ on rock and groundwater samples. In the last decade, stable Cr isotopic measurements were performed by combining the double‐spike technique and multi‐collector mass spectrometry, with long‐term reproducibilities (2SD) of around 0.05‰ to 0.06‰ being reported. In 2014, Schiller et al reported a sample‐standard bracketing (SSB) method for Cr isotopic measurements.…”