Measurement of zinc stable isotope ratios in biogeochemical matrices by double-spike MC-ICPMS and determination of the isotope ratio pool available for plants from soil

Maria Schonbachler, Tim Arnold, Maria Schönbächler, Mark Rehkämper, Schuofei Dong, Fang Jie Zhao, Guy J D Kirk, Barry J. Coles, Dominik J. Weiss

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Analysis of naturally occurring isotopic variations is a promising tool for investigating Zn transport and cycling in geological and biological settings. Here, we present the recently installed double-spike (DS) technique at the MAGIC laboratories at Imperial College London. The procedure improves on previous published DS methods in terms of ease of measurement and precisions obtained. The analytical method involves addition of a 64Zn-67Zn double-spike to the samples prior to digestion, separation of Zn from the sample matrix by ion exchange chromatography, and isotopic analysis by multiple-collector inductively coupled plasma mass spectrometry. The accuracy and reproducibility of the method were validated by analyses of several in-house and international elemental reference materials. Multiple analyses of pure Zn standard solutions consistently yielded a reproducibility of about ±0.05‰ (2 SD) for δ66Zn, and comparable precisions were obtained for analyses of geological and biological materials. Highly fractionated Zn standards analyzed by DS and standard sample bracketing yield slightly varying results, which probably originate from repetitive fractionation events during manufacture of the standards. However, the δ66Zn values (all reported relative to JMC Lyon Zn) for two less fractionated in-house Zn standard solutions, Imperial Zn (0.10∈±∈0.08‰: 2 SD) and London Zn (0. 08∈±∈0.04‰), are within uncertainties to data reported with different mass spectrometric techniques and instruments. Two standard reference materials, blend ore BCR 027 and ryegrass BCR 281, were also measured, and the δ66Zn were found to be 0.25∈±∈0. 06‰ (2 SD) and 0.40∈±∈0.09‰, respectively. Taken together, these standard measurements ascertain that the double-spike methodology is suitable for accurate and precise Zn isotope analyses of a wide range of natural samples. The newly installed technique was consequently applied to soil samples and soil leachates to investigate the isotopic signature of plant available Zn. We find that the isotopic composition is heavier than the residual, indicating the presence of loosely bound Zn deposited by atmospheric pollution, which is readily available to plants. [Figure not available: see fulltext.] © 2010 The Author(s).
    Original languageEnglish
    Pages (from-to)3115-3125
    Number of pages10
    JournalAnalytical and bioanalytical chemistry
    Volume398
    Issue number7-8
    DOIs
    Publication statusPublished - Dec 2010

    Keywords

    • Double-spike
    • Mass bias correction
    • MC-ICPMS
    • Soil biogeochemistry
    • Stable isotope fractionation
    • Zinc isotopes

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