Isotopic delta values of molybdenum standard reference and prepared solutions measured by MC-ICP-MS: Proposition for delta zero and secondary references

Abstract

We report the isotopic composition of five molybdenum (Mo) standard reference solutions and four fractions from one of these solutions eluted through anion resin column relative to a sixth reference solution. The reference solutions were National Institute of Standards and Technology (NIST) SRM 3134 (lot#891307), Johnson Matthey Specpure (JMC)-Mo Sie (lot #602332B), JMC-Mo Wen (lot#13989C), Merck (lot#170334), Sigma-Aldrich (lot#207306) and Prolabo. Measurements were conducted using Isoprobe multi collector inductively coupled plasma mass spectrometer (MC-ICP-MS) at the Centre de Recherches P etrographiques et G eochimiques (France) and Nu Plasma MC-ICP-MS at either the Ecole Normale Sup erieure de Lyon (France) or the Laboratory of Isotope Geology in the Ministry of Land and Resources (China). The sample-standard bracketing method was employed to correct the mass bias for Mo isotopes during instrumental measurement. Except for the Merck Mo solution, all the Mo solutions were identical in isotopic composition within error. Although the JMC Mo solution has been used as the internal reference material by various groups, uncertainty may still occur with different lot numbers and availability might be limited. Here, we propose the NIST 3134 Mo solution as a new candidate for delta zero reference material, used for reporting Mo isotopic composition of natural samples. Isotopic compositions for four eluted fractions of the Sigma-Aldrich Mo solution were 2.18&, 0.98&, À1.10& and À1.95& for d 97/95 Mo relative to the NIST Mo standard. These values span the range of reported isotopic compositions for natural terrestrial and experimental samples (approximately À0.5& to 1.6& for d 97/95 Mo). We propose these eluted fractions to be used as a secondary reference for Mo isotope measurements. Mo solutions are available at CRPG upon request.

Molybdenum Mass Fractions and Isotopic Compositions of International Geological Reference Materials

“…The NIST SRM 3134 Mo solution has been proposed as a universal zero-delta reference material for expressing Mo isotope data in delta notation for natural samples (Wen et al 2010, Greber et al 2012, Goldberg et al 2013. As demonstrated by Greber et al (2012) and Goldberg et al (2013) (Dodson 1963).…”

Assessment of international reference materials for isotope-ratio analysis (IUPAC Technical Report)

“…Unfortunately, no internationally accepted reference material was available, and therefore each group used its own isotopic reference material. This problem has been recognized, and recently different reference materials have been analyzed relative to each other [251,252], including the material used as the best measurement for defining the Mo atomic weight (NIST SRM 3134) [253,254,258]. This material, which is an atomic spectrometry standard provided by NIST, has been proposed as an anchor point for the δ 98/95 Mo [251] 9 .…”

“…This problem has been recognized, and recently different reference materials have been analyzed relative to each other [251,252], including the material used as the best measurement for defining the Mo atomic weight (NIST SRM 3134) [253,254,258]. This material, which is an atomic spectrometry standard provided by NIST, has been proposed as an anchor point for the δ 98/95 Mo [251] 9 . Mean Ocean Molybdenum (MOMo) δ 98/95 Mo has been measured as +2.09 ± 0.07 ‰ relative to NIST SRM 3134 [252] by analysis of five IAPSO ampoules (four from the Atlantic and one from the Mediterranean).…”

Molybdenum isotopic composition as a tracer for low-medium temperature hydrothermal ore-forming systems: A case study on the Dajiangping pyrite deposit, western Guangdong Province, China

“…Results are reliable and satisfied with the quality control criteria. a) The reference values of SG-2 and SG-3 are quoted from Wen et al [28].…”

“…Because there are few universally acknowledged Mo isotopic international standards, a latest calibrating NIST SRM 3134 solution recommend by Wen et al [28] was used as an internal reference standard. Meanwhile, Wen et al suggested that the current international internal isotope laboratory using various criteria, such as JMC, Merck, NIST SRM 3134, with its Mo isotopic composition is consistent within errors [28].…”