Cadmium Isotope Ratios of Standard Solutions and Geological Reference Materials Measured by MC‐ICP‐MS

Abstract

We report high‐precision cadmium isotope ratios for a series of standard solutions and geological reference materials for interlaboratory comparison. Complete separation of Cd from a matrix in geological samples was achieved using AG MP‐1M anion exchange resin with > 97.8% recovery. Cadmium isotope ratios were measured by both Neptune plus multi‐collector‐inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS) and Nu Plasma II MC‐ICP‐MS at low‐resolution mode. Both sample calibrator bracketing (SSB) and double‐spike techniques (DS) were utilised for mass bias correction. Cadmium isotope ratio data of standard solutions (BAM I012 Cd, SPEX Cd, Alfa Aesar Cd, GSB Cd) and geological reference materials (GSS‐1, GXR‐1, GXR‐2, GSD‐12, NIST SRM 2711a) are reported relative to Cd solution (NIST SRM 3108). The intermediate precision over a three‐year period was better than ± 0.09‰ (2s) for δ114Cd/110Cd and ± 0.06‰ (2s) for δ112Cd/110Cd ratios. SPEX Cd was used as a secondary reference material for Cd isotopic measurement with a δ114/110CdNIST SRM 3108 value of −2.13 ± 0.09‰ (2s). The soil reference material NIST SRM 2711a has a significantly heavier isotopic composition than other soil materials, GXR‐1, GXR‐2 and GSS‐1. New recommended values are presented for future interlaboratory calibration.

High‐Precision Cd Isotope Measurements of Soil and Rock Reference Materials by MC‐ICP‐MS with Double Spike Correction

“…The Cd mass fractions of soil reference materials were reported by NIST and IGGE, and most of the values for rock reference materials were determined by isotope dilution mass spectrometry in this study. With the exception of GSS‐1 and NOD‐P‐1, only minimal Cd isotope data for NIST SRM 2709, 2709a, 2711, 2711a, BIR‐1, and AGV‐2 have been reported (Cloquet et al , Pallavicini et al , Wiggenhauser et al , Palk et al , Imseng et al , Li et al ), and the Cd isotope values of some of the reference materials are reported for the first time in this study.…”

“…, Li et al . ); other symbols represent the data from this study. Errors of data from the literature and this study reflect two standard deviations (2 s ).…”

“…With advances in instrumentation, increasingly high precision Cd isotope measurement results have been reported using different chemical purification procedures and different instrumental analysis methods (e.g., Wombacher et al , Cloquet et al , Ripperger and Rehkämper , Gao et al , Schmitt et al , Xue et al , Li et al ). The Cd isotopes of different types of samples with low Cd mass fractions including organic materials, plants, carbonates, silicate rocks, river sediments, seawater and meteorites have been determined precisely and accurately (e.g., Rosman and De Laeter , Cloquet et al , Ripperger and Rehkämper , Gao et al , Wombacher et al , Schmitt et al , Abouchami et al , Pallavicini et al , Georgiev et al , Wei et al , Wiggenhauser et al , Wen et al , Hohl et al , John et al , Imseng et al , Li et al , Viehman et al ). The mass bias produced by the instrument has been corrected by different methods including sample‐calibrator bracketing, and the Ag doping and double spike method (Wombacher et al , Cloquet et al , Ripperger and Rehkämper , Schmitt et al , Li et al ).…”

“…The Cd isotopes of different types of samples with low Cd mass fractions including organic materials, plants, carbonates, silicate rocks, river sediments, seawater and meteorites have been determined precisely and accurately (e.g., Rosman and De Laeter , Cloquet et al , Ripperger and Rehkämper , Gao et al , Wombacher et al , Schmitt et al , Abouchami et al , Pallavicini et al , Georgiev et al , Wei et al , Wiggenhauser et al , Wen et al , Hohl et al , John et al , Imseng et al , Li et al , Viehman et al ). The mass bias produced by the instrument has been corrected by different methods including sample‐calibrator bracketing, and the Ag doping and double spike method (Wombacher et al , Cloquet et al , Ripperger and Rehkämper , Schmitt et al , Li et al ). The double spike method can accurately correct mass fractionation produced by the chemical purification process and instrumental mass bias, and an increasing number of laboratories have chosen to use the double spike method in recent Cd isotope studies (Schmitt et al , Rehkämper et al ).…”

“…It is of critical importance to correct the interference effects in Cd isotope measurement. The study performed by Wombacher et al () and other studies (e.g., Cloquet et al , Horner et al , Pallavicini et al , Li et al ) evaluated in detail the effects of molecular and isobaric interferences using MC‐ICP‐MS and found that even a large amount of Sn in the sample solutions can still be accurately corrected, whereas limited tolerance for Ru and Zn was found. The effects of Pd and In on Cd isotope measurement were also evaluated in previous studies, but the precise Pd/Cd and In/Cd ratios that can be tolerated in sample solutions are still unknown.…”