Progress of Analytical Techniques for Stable Iron Isotopes
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ABSTRACT
BACKGROUNDIron is the most abundant element on earth with variable valences. It is widely distributed in various minerals, rocks, fluids and organisms, and is involved in diagenesis, mineralization, hydrothermal activities and life activities. The study of iron isotope composition provides important information for geochemistry, astrochemistry and biochemistry. The accurate measurement of Fe isotopes is an important basis for the development of related research.OBJECTIVESTo summarize the research progress of Fe isotope measurement technology.METHODSThe current chemical separation and purification methods and main instrumental analysis techniques commonly used for iron isotopes, were compared and analyzed in this review, and the mechanism of different types of fractionations during mass spectrometry were discussed. These advances included:(1) Improvement of anion resin during determination of iron isotope by solution method; (2) Mass spectrometry development from traditional thermal ionization mass spectrometry to multi-collector inductively coupled plasma mass spectrometry; (3) Development of laser in situ analytical technology. On this basis, the steps and calibration methods that would cause iron isotope fractionation during the analysis were summarized, and the advantages and disadvantages of different analytical methods were reviewed.RESULTSThe analysis process of solution method was long and complicated, but the precision was high (0.03‰, 2SD) and the method was stable. In situ iron isotope analysis method developed from nanosecond laser denudation to femtosecond laser denudation, with shorter pulse duration, higher pulse peak intensity (up to 1012W), and focusing intensity exceeding 1020W/cm2. In situ iron isotope analysis method was fast and had high spatial resolution, which can be used to discuss the geochemical process from the microscopic perspective. However, the presence of matrix effects limited the widespread use of iron isotopes.CONCLUSIONSShortening solution analysis process and developing a series of matrix-matched standard samples are the research direction of iron isotope analysis.
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