Anion-exchange chromatographic separation of Hg for isotope ratio measurements by multicollector ICPMS.
A procedure is described for precise Hg isotope ratio measurements by solution nebulization multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Hg was released from geological samples using aqua regia extraction and then separated from other matrix elements with the aid of anion-exchange chromatography using strongly basic Dowex 1-X8 anion-exchange resin. Performance of the chromatographic procedure was evaluated using various types of replacement anions for elution of mercury, including l-cysteine, thiourea, NO3-, and SO42-. A solution of 0.15% l-cysteine in 0.06 M HCl was found to be the most convenient eluent for subsequent MC-ICPMS measurements. The optimized procedure provides separation of Hg from virtually all concomitant matrix elements while maintaining quantitative (>95%) recovery. In addition, band displacement chromatographic experiments were conducted to assess whether the anion-exchange purification can produce Hg isotope fractionation artifacts. No isotope fractionation between the Hg(II)-l-cysteine complex in aqueous solution and Hg ions in the anion-exchange resin was observed. Hg isotope ratio measurements were performed using the bracketing standards approach and on-line correction for instrumental mass discrimination using Tl spiking and normalization to the 205Tl/203Tl ratio. The absence of spectral interference during Hg isotope ratio measurements was verified using a three-isotope plot. Uncertainties of Hg isotope ratio measurements for replication of the entire procedure, expressed as two standard deviations, are better than +/-0.08 per thousand/amu. The described procedure facilitates study of variations in the isotopic composition of Hg in nature.
Malinovsky
Dmitry
D
Institute for National Measurement To whom correspondences should be Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada. maldima@yandex.ru
Sturgeon
Ralph E
RE
Yang
Lu
L
D000838:Anions / Q000737:chemistry; D002852:Chromatography, Ion Exchange / Q000379:methods*; D007554:Isotopes; D013058:Mass Spectrometry / Q000379:methods*; D008628:Mercury / Q000737:chemistry* / Q000302:isolation & purification*
D000838:Anions; D007554:Isotopes; D008628:Mercury