Fe Isotope Variations in Natural Materials Measured Using High Mass Resolution Multiple Collector ICPMS

• Published in: Analytical chemistry (Washington) Vol. 76; no. 2; pp. 322 - 327
• Main Authors: Arnold, G. L, Weyer, S, Anbar, A. D
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-01-2004
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Isotopes; Measurement; Natural resources; Plasma; Spectrometric and optical methods; Spectrum analysis; Iron isotopes; High resolution; Sample preparation; Coupled method; Reproducibility; Internal standard; Simultaneous measurement; Collector; Ion beam; Isotopic composition; Inductive coupling plasma spectrometry; Mass spectrometry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac034601v

We present the first measurements of Fe isotope variations in chemically purified natural samples using high mass resolution multiple-collector inductively coupled plasma source mass spectrometry (MC-ICPMS). High mass resolution allows polyatomic interferences at Fe masses to be resolved (especially, 40Ar14N+, 40Ar16O+, and 40Ar16OH+). Simultaneous detection of Fe isotope ion beams using multiple Faraday collectors facilitates high-precision isotope ratio measurements. Fe in basalt and paleosol samples was extracted and purified using a simple, single-stage anion chemistry procedure. A Cu “element spike” was used as an internal standard to correct for variations in mass bias. Using this procedure, we obtained data with an external precision of 0.03−0.11‰ and 0.04−0.15‰ for δ56/54Fe and δ57/54Fe, respectively (2σ). Use of Cu was necessary for such reproducibility, presumably because of subtle effects of residual sample matrix on mass bias. These findings demonstrate the utility of high-resolution MC-ICPMS for high-precision Fe isotope analysis in geologic and other natural materials. They also highlight the importance of internal monitoring of mass bias, particularly when using routine methods for Fe extraction and purification.