Jump to main content
Jump to site search

High-sensitivity determination of Cd isotopes in low-Cd geological samples by double spike MC-ICP-MS


With new advancements in MC-ICP-MS technology, small Cd isotope fractionations in geological processes have attracted more interests in recent years. However, challenges remain in obtaining high-precision Cd isotope data for geological samples with low Cd concentrations and complex matrices. By an improved Cd purification and cleaning resin scheme for low-Cd samples using AGMP-1M resin with >90% Cd recovery, the ratios of trace elements Sn, Mo, Zr, etc. to Cd in the samples, which could potentially jeopardize the accuracy and precision of Cd isotopes analysis under high-sensitivity setup, were less than 0.001 after purification, and the total procedure blank is ≤0.1 ng. Hence, sample size containing 20-30ng Cd can be employed to purify for isotope measurement. Cadmium isotope fractionation (expressed in δ114/110Cd relative to NIST 3108) during column separation and instrument mass bias was corrected for by a 111Cd-113Cd double spike. NIST 3108 was determined at a concentration of 5 -25 ng mL-1 on Neptune Plus (112Cd signal intensity:~640V/ppm) and 25 -50 ng mL-1 on Nu plasma III (112Cd signal intensity:~280V/ppm) MC-ICP-MS equipped with Aridus II/III desolvator for more than one year, with a totally external analytical precision of 0.034‰ (2SD, N=181). The NIST SRM 2711a, NOD-P-1 and GSS-1 were measured at 5, 10, 20, 25 and 50 ng mL-1 level to be 0.532±0.038‰, 0.133±0.038‰ and 0.098±0.027‰, respectively, indicating good accuracy and precision of Cd isotope analysis can be achieved with an injecting sample size as low as 5 ng Cd. Our method can be reliably applied to various geological reference materials (GRMs). The δ114/110Cd of GRMs with relatively high and low Cd concentrations are consistent with previous studies: NOD-A-1(0.124±0.067‰), GSD-11 (-0.274±0.037‰) and BCR-2 (-0.030±0.063‰). The SGR-1b (0.069±0.049‰), GSH-1(-0.337±0.077‰) and others are reported for the first time in this paper. The δ114/110Cd in basalts and stream sediments is relatively homogenous and overlaps with that of the bulk silicate earth (BSE). The δ114/110Cd in shales and soils varies greatly from -0.694 to 0.532‰. Human hair and other animal organs are enriched in light isotopes relative to BSE, whereas terrestrial plants are enriched in heavy isotopes.

Back to tab navigation

Supplementary files

Article information

20 Nov 2019
14 Jan 2020
First published
15 Jan 2020

J. Anal. At. Spectrom., 2020, Accepted Manuscript
Article type

High-sensitivity determination of Cd isotopes in low-Cd geological samples by double spike MC-ICP-MS

D. Tan, J. Zhu, X. Wang, G. Han, Z. Lu and W. Xu, J. Anal. At. Spectrom., 2020, Accepted Manuscript , DOI: 10.1039/C9JA00397E

Social activity

Search articles by author