The isotopic composition of iron, zinc, copper, and cadmium (δ56Fe, δ66Zn, δ65Cu, and δ114Cd) are novel and promising tools to study the metabolism and homeostasis of trace metals in the human body. Serum δ65Cu has been proposed as a potential tool for diagnosis of cancer in liquid biopsy, and other metals may have similar utility. However, accurate analysis of trace metal isotopes is challenging because of the difficulties in purifying the metals from biological samples. Here we developed a simple and rapid method for sequential purification of Cu, Fe, Zn, and Cd from a single blood plasma sample. By using a combination of 11 M acetic acid and 4 M HCl in the first steps of column chemistry on AG-MP1 resin, we dramatically improve the separation of Cu from matrix elements compared to previous methods which use concentrated HCl alone. Our new method achieves full recovery of Cu, Fe, Zn, and Cd to prevent column-induced isotope fractionation effects, and effectively separates analytes from the matrix in order to reduce polyatomic interferences during isotope analysis. Our methods were verified by the analysis of isotope standards, a whole blood reference material, and a preliminary sample set including five plasma samples from healthy individuals and five plasma samples from cancer patients. This new method simplifies preparation of blood samples for metal isotope analysis, accelerating multi-isotope approaches to medical studies and contributing to our understanding of the cycling of Fe, Zn, Cu, and Cd in the human body.
δ56Fe δ66Zn δ65Cu δ114Cd Chromatography Blood
This is a preview of subscription content, log in to check access.
We would like to thank Nick Hawco, Paulina Pinedo-Gonzalez, and Irit Tal for technical support. We would also like to thank Editor Alfredo Sanz-Medel and two anonymous referees for their helpful comments.
This work was supported by NSF award 1636332.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All sampling procedures were approved by the University of Southern California, University Park Institutional Review Board (FWA no. 00007099), and the Scripps Health Green Hospital Institutional Review Board (FWA no. 00000411). All study participants provided written informed consent.
Dauphas N, John SG, Rouxel O. Iron isotope systematics. Rev Mineral Geochem. 2017;82:415–510.CrossRefGoogle Scholar
Moynier F, Vance D, Fujii T, Savage P. The isotope geochemistry of zinc and copper. Rev Mineral Geochem. 2017;82:543–600.CrossRefGoogle Scholar
Teng FZ, Dauphas N, Watkins JM. Non-traditional stable isotopes: retrospective and prospective. Rev Mineral Geochem. 2017;82:1–26.CrossRefGoogle Scholar
Albarède F, Télouk P, Balter V, Bondanese VP, Albalat E, Oger P, et al. Medical applications of Cu, Zn, and S isotope effects. Metallomics. 2016;8:1056–70.CrossRefGoogle Scholar
Albarède F, Telouk P, Lamboux A, Jaouen K, Balter V. Isotopic evidence of unaccounted for Fe and Cu erythropoietic pathways. Metallomics. 2011;3:926–33.CrossRefGoogle Scholar
Balter V, da Costa AN, Bondanese VP, Jaouen K, Lamboux A, Sangrajrang S, et al. Natural variations of copper and sulfur stable isotopes in blood of hepatocellular carcinoma patients. Proc Natl Acad Sci U S A. 2015;112:982–5.CrossRefGoogle Scholar
Télouk P, Puisieux A, Fujii T, Balter V, Bondanese VP, Morel AP, et al. Copper isotope effect in serum of cancer patients. A pilot study. Metallomics. 2015;7:299–308.CrossRefGoogle Scholar
Dauphas N, Janney PE, Mendybaev RA, Wadhwa M, Richter FM, Davis AM, et al. Chromatographic separation and multicollection-ICPMS analysis of iron. Investigating mass-dependent and-independent isotope effects. Anal Chem. 2004;76:5855–63.CrossRefGoogle Scholar
Maréchal CN, Télouk P, Albarède F. Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry. Chem Geol. 1999;156:251–73.CrossRefGoogle Scholar
Heghe LV, Engström E, Rodushkin I, Cloquet C, Vanhaecke F. Isotopic analysis of the metabolically relevant transition metals Cu, Fe and Zn in human blood from vegetarians and omnivores using multi-collector ICP-mass spectrometry. J Anal At Spectrom. 2012;27:1327–34.CrossRefGoogle Scholar
Borrok DM, Wanty RB, Ridley WI, Wolf R, Lamothe PJ, Adams M. Separation of copper, iron, and zinc from complex aqueous solutions for isotopic measurement. Chem Geol. 2007;242:400–14.CrossRefGoogle Scholar
Conway TM, Rosenberg AD, Adkins JF. John SG. A new method for precise determination of iron, zinc and cadmium stable isotope ratios in seawater by double-spike mass spectrometry. Anal Chim Acta. 2013;793:44–52.CrossRefGoogle Scholar
Zhu ZY, Jiang SY, Yang T, Wei HZ. Improvements in Cu–Zn isotope analysis with MC-ICP-MS: a revisit of chemical purification, mass spectrometry measurement and mechanism of Cu/Zn mass bias decoupling effect. Int J Mass Spectrom. 2015;393:34–40.CrossRefGoogle Scholar
Korkisch J. CRC handbook of ion exchange resins, vol. 6: CRC Press; 1988. 154ppGoogle Scholar
Chapman JB, Mason TF, Weiss DJ, Coles BJ, Wilkinson JJ. Chemical separation and isotopic variations of Cu and Zn from five geological reference materials. Geostand Geoanal Res. 2006;30:5–16.CrossRefGoogle Scholar
Larner F, Rehkämper M, Coles BJ, Kreissig K, Weiss DJ, Sampson B, et al. A new separation procedure for Cu prior to stable isotope analysis by MC-ICP-MS. J Anal At Spectrom. 2011;26:1627–32.CrossRefGoogle Scholar
Fritz JS, Pietrzyk DJ. Non-aqueous solvents in anion-exchange separations. Talanta. 1961;8:143–62.CrossRefGoogle Scholar
Korkisch J, Hazan I. Anion exchange separations in hydrobromic acid-organic solvent media. Anal Chem. 1965;37:707–10.CrossRefGoogle Scholar
Klakl E, Korkisch J. Anion-exchange behaviour of several elements in hydrobromic acid-organic solvent media. Talanta. 1969;16:1177–90.CrossRefGoogle Scholar
Marrinucci D, Bethel K, Kolatkar A, Luttgen MS, Malchiodi M, Baehring F, et al. Fluid biopsy in patients with metastatic prostate, pancreatic and breast cancers. Phys Biol. 2012;9:016003.CrossRefGoogle Scholar
Gault-Ringold M, Stirling CH. Anomalous isotopic shifts associated with organic resin residues during cadmium isotopic analysis by double spike MC-ICPMS. J Anal At Spectrom. 2012;27:449–59.CrossRefGoogle Scholar
Takano S, Tanimizu M, Hirata T, Shin KC, Fukami Y, Suzuki K, et al. A simple and rapid method for isotopic analysis of nickel, copper, and zinc in seawater using chelating extraction and anion exchange. Anal Chim Acta. 2017;967:1–11.CrossRefGoogle Scholar
Mason TF, Weiss DJ, Horstwood M, Parrish RR, Russell SS, Mullane E, et al. High-precision Cu and Zn isotope analysis by plasma source mass spectrometry part 2. Correcting for mass discrimination effects. J. Anal Atom Spectrom. 2004;19:218–26.CrossRefGoogle Scholar
Siebert C, Nägler TF, Kramers JD. Determination of molybdenum isotope fractionation by double-spike multicollector inductively coupled plasma mass spectrometry. Geochem Geophys Geosyst. 2001;2:2000GC000124.CrossRefGoogle Scholar
Hou Q, Zhou L, Gao S, Zhang T, Feng L, Yang L. Use of Ga for mass bias correction for the accurate determination of copper isotope ratio in the NIST SRM 3114 Cu standard and geological samples by MC-ICPMS. J Anal At Spectrom. 2015;31:280–7.CrossRefGoogle Scholar
Strelow FW. Distribution coefficients and anion exchange behavior of some elements in hydrobromic-nitric acid mixtures. Anal Chem. 1978;50:1359–61.CrossRefGoogle Scholar
Abouchami W, Galer SJ, Horner TJ, Rehkämper M, Wombacher F, Xue Z, et al. A common reference material for cadmium isotope studies–NIST SRM 3108. Geostand Geoanal Res. 2012;37:5–17.CrossRefGoogle Scholar
Stevenson EI, Fantle MS, Das SB, Williams HM, Aciego SM. The iron isotopic composition of subglacial streams draining the Greenland ice sheet. Geochim Cosmochim Acta. 2017;213:237–54.CrossRefGoogle Scholar
Miller KA, Keenan CM, Martin GR, Jirik FR, Sharkey KA, Wieser ME. The expression levels of cellular prion protein affect copper isotopic shifts in the organs of mice. J Anal At Spectrom. 2016;31:2015–22.CrossRefGoogle Scholar
Costas-Rodríguez M, Anoshkina Y, Lauwens S, Van Vlierberghe H, Delanghe J, Vanhaecke F. Isotopic analysis of Cu in blood serum by multi-collector ICP-mass spectrometry: a new approach for the diagnosis and prognosis of liver cirrhosis? Metallomics. 2015;7:491–8.CrossRefGoogle Scholar
Anoshkina Y, Costas-Rodríguez M, Speeckaert M, Van Biesen W, Delanghe J, Vanhaecke F. Iron isotopic composition of blood serum in anemia of chronic kidney disease. Metallomics. 2017;9:517–24.CrossRefGoogle Scholar