title: Hg stable isotope analysis by the double-spike method.
abstract: Recent publications suggest great potential for analysis of Hg stable isotope abundances to elucidate sources and/or chemical processes that control the environmental impact of mercury. We have developed a new MC-ICP-MS method for analysis of mercury isotope ratios using the double-spike approach, in which a solution containing enriched (196)Hg and (204)Hg is mixed with samples and provides a means to correct for instrumental mass bias and most isotopic fractionation that may occur during sample preparation and introduction into the instrument. Large amounts of isotopic fractionation induced by sample preparation and introduction into the instrument (e.g., by batch reactors) are corrected for. This may greatly enhance various Hg pre-concentration methods by correcting for minor fractionation that may occur during preparation and removing the need to demonstrate 100% recovery. Current precision, when ratios are normalized to the daily average, is 0.06 per thousand, 0.06 per thousand, 0.05 per thousand, and 0.05 per thousand (2sigma) for (202)Hg/(198)Hg, (201)Hg/(198)Hg, (200)Hg/(198)Hg, and (199)Hg/(198)Hg, respectively. This is slightly better than previously published methods. Additionally, this precision was attained despite the presence of large amounts of other Hg isotopes (e.g., 5.0% atom percent (198)Hg) in the spike solution; substantially better precision could be achieved if purer (196)Hg were used.
authors.affiliation: Arizona State University, School of Earth and Space Exploration, P.O. Box 871404, Tempe, AZ 85287, USA. chris.mead@asu.edu
authors.forename: Chris
authors.initials: C
authors.lastname: Mead
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Johnson
mesh_terms: D013058:Mass Spectrometry / Q000379:methods*; D008629:Mercury Isotopes / Q000032:analysis
chemical_list: D008629:Mercury Isotopes