Matrix and energy effects during in-situ determination of Cu isotope ratios by ultraviolet-femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry
Matrix and energy effects during in-situ determination of Cu isotope ratios by ultraviolet-femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry
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DOI：
10.1016/j.sab.2015.06.013
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发表时间：
2015-09-01
影响因子：
3.3
通讯作者：
Horn, Ingo
中科院分区：
文献类型：
--
作者：
Lazarov, Marina;Horn, Ingo
采用深紫外飞秒激光烧蚀多接收器电感耦合等离子体质谱（UV-fsLA-MC-ICP-MS）测定了含铜金属和矿物中铜同位素组成。研究了纯铜金属、黄铜和几种富铜矿物（黄铜矿、硫砷铜矿、铜蓝、孔雀石和赤铜矿）。在NIST SRM 976（美国国家标准与技术研究所）铜金属标准的95%置信限下，该技术的长期重现性优于0.08份/千份。采用HIST SRM 976，通过标准品-样品-标准品交叉进样计算所有样品的Δ Cu-65值。在进入等离子体炬之前，使用Ni作为通过雾化添加的质量鉴别监测器进行所有分析。为了进一步验证，已通过常规溶液雾化MC-ICP-MS分析样品，并将所得结果与UV-fsLA-MC-ICP-MS的结果进行了比较。（S-32-（OO）-O-16-O-17）（+）不影响硫化物的Cu同位素测量，而干扰Ni同位素的杂质，如Zn-H或双电荷Sn ~（2+），可以忽略或通过计算去除。与基体无关的Cu同位素测量对施加到样品上的能量密度（注量）敏感，并且当使用高达2 J/cm（2）的能量密度进行烧蚀时，可以在所获得的Δ Cu-65值中产生人为偏移，对于Cu金属，Δ Cu-65值大约为千分之3，对于黄铜，Δ Cu-65值大约为千分之0.5，对于孔雀石，Δ Cu-65值大约为千分之0.3。在能量密度为0.2 ~ 1.3J/cm（2）的范围内（低于ns激光烧蚀的阈值），所施加的能量密度与同位素比移动的幅度之间存在正相关关系。结果表明，通过使用适当的低能量密度，它是可能的测量Cu同位素比率在自然铜和含Cu的硫化物，碳酸盐和氧化物在原位的精度优于0.1千分之一（2SD），而不使用基质匹配的标准在激光烧蚀分析。因此，这是一个合适的工具来解决铜硫化物，碳酸盐和氧化物中大于0.1千分之一的铜同位素分带。(C)2015 Elsevier B. V.版权所有。
Copper isotope compositions in Cu-bearing metals and minerals have been measured by deep (194 nm) ultraviolet femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (UV-fsLA-MC-ICP-MS). Pure Cu-metal, brass, and several Cu-rich minerals (chalcopyrite, enargite, covellite, malachite and cuprite) have been investigated. A long-term reproducibility of better than 0.08 parts per thousand at the 95% confidence limit on the NIST SRM 976 (National Institute of Standards and Technology) Cu-metal standard has been achieved with this technique. The delta Cu-65 values for all samples have been calculated by standard-sample-standard bracketing with HIST SRM 976. All analyses have been carried out using Ni as a mass discrimination monitor added by nebulization prior to entering the plasma torch. For further verification samples have been analysed by conventional solution nebulization MC-ICP-MS and the results obtained have been compared with those from UV-fsLA-MC-ICP-MS. Several potential matrix-induced molecular interferences on the mineral copper isotope ratio, such as ((SS)-S-32-S-33)(+) and (S-32-(OO)-O-16-O-17)(+) do not affect the Cu isotope measurements on sulfides, while hydrides, such as Zn-H or doubly-charged Sn2+ that interfere Ni isotopes can be either neglected or stripped by calculation. Matrix independent Cu-isotope measurements are sensitive to the energy density (fluence) applied onto the sample and can produce artificial shifts in the obtained delta Cu-65 values which are on the order of 3 parts per thousand for Cu-metal, 0.5 parts per thousand for brass and 0.3 parts per thousand for malachite when using energy density of up to 2 J/cm(2) for ablation. A positive correlation between applied energy density and the magnitude of the isotope ratio shift has been found in the energy density range from 0.2 to 1.3 J/cm(2) which is below the ablation threshold for ns-laser ablation. The results demonstrate that by using appropriate low fluence it is possible to measure Cu isotopic ratios in native copper and Cu-bearing sulfides, carbonates and oxides in situ with a precision of better than 0.1 parts per thousand (2SD) without using a matrix-matched standard during laser ablation analyses. Thus, this is a suitable tool to resolve Cu isotopic zoning larger than 0.1 parts per thousand in Cu-sulfides, carbonates and oxides. (C) 2015 Elsevier B.V. All rights reserved.