A Common Reference Material for Cadmium Isotope Studies – NIST SRM 3108

Abstract

Research into natural mass‐dependent stable isotope fractionation of cadmium has rapidly expanded in the past few years. Methodologies are diverse with MC‐ICP‐MS favoured by all but one laboratory, which uses thermal ionisation mass spectrometry (TIMS). To quantify the isotope fractionation and correct for instrumental mass bias, double‐spike techniques, sample‐calibrator bracketing or element doping has been used. However, easy comparison between data sets has been hampered by the multitude of in‐house Cd solutions used as zero‐delta reference in different laboratories. The lack of a suitable isotopic reference material for Cd is detrimental for progress in the long term. We have conducted a comprehensive round‐robin assay of NIST SRM 3108 and the Cd isotope offsets to commonly used in‐house reference materials. Here, we advocate NIST SRM 3108 both as an isotope standard and the isotopic reference point for Cd and encourage its use as ‘zero‐delta’ in future studies. The purity of NIST SRM 3108 was evaluated regarding isobaric and polyatomic molecular interferences, and the levels of Zn, Pd and Sn found were not significant. The isotope ratio 114Cd/110Cd for NIST SRM 3108 lies within ∼ 10 ppm Da−1 of best estimates for the Bulk Silicate Earth and is validated for all measurement technologies currently in use.

Cadmium Isotope Fractionation in Soil–Wheat Systems

“…These measurements yielded δ 114/110 Cd = -1.30 ± 0.09 (2sd, n = 12), in good agreement with the consensus value of -1.33 ± 0.04. 6 The Cd isotope compositions and contents of three geological and biological SRMs with matrices and…”

“…4,5 More recently, several studies conducted 48 isotopic analyses of micronutrients, including Zn [6][7][8] , Cu 7,9 , Fe 10,11 and Ni…”

Chromatographic Separation of Cd from Plants via Anion-Exchange Resin for an Isotope Determination by Multiple Collector ICP-MS

“…18,19,25,36 It is clear that the Cd isotopic composition was different if the laboratories used their own Cd reference solutions as "zero-delta". Based on this situation, Abouchami et al 10 calibrated the Cd isotope values of the Cd reference materials in different laboratories and advocated NIST SRM 3108 as the Cd isotope standard for "zero-delta" in future studies firstly. In this study, four second Cd standard solutions were measured and the 114/110 Cd of Münster Cd, Spex Cd, Spex-1 Cd solutions relative to the NIST SRM 3108 were +4.45 ± 0.08 (2SD, N = 12), -0.09 ± 0.01 (2SD, N = 2), -1.25 ± 0.06 (2SD, N = 3), respectively.…”

“…10,37 Most laboratories used their own and in-house Cd reference materials for "zero-delta", such as BAM 1012, JMC Cd Münster, Alfa Cd Zürich, JMC Cd Mainz, NIST SRM 3108, Münster Cd, and so on. 18,19,25,36 It is clear that the Cd isotopic composition was different if the laboratories used their own Cd reference solutions as "zero-delta".…”

“…[3][4][5][6][7][8] Especially, the recent advent in multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) has extended dramatically the range of applications of stable Cd isotopes as tracers in natural systems. 9,10 Cd isotope analyses have been applied in order to investigate the evolution of celestial bodies, [11][12][13] mineral genesis and material source, 7,14 paleo-ocean environments, [15][16][17][18][19] and environmental cadmium pollution sources. 3,4,8,[20][21][22] Furthermore, Wei et al 6 suggested that Cd isotope fractionation in Cd hyperaccumulator plants could apply new insights in the enrichment mechanisms.…”