Direct Determination of Lead Isotopes (206Pb, 207Pb, 208Pb) in Arctic Ice Samples at Picogram per Gram Levels Using Inductively Coupled Plasma-Sector Field MS Coupled

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• 作者：Michael Krachler ; James Zheng ; David Fisher ; and William Shotyk
• 刊名：Analytical Chemistry
• 出版年：2004
• 出版时间：September 15, 2004
• 年：2004
• 卷：76
• 期：18
• 页码：5510 - 5517
• 全文大小：97K
• 年卷期：v.76,no.18(September 15, 2004)
• ISSN：1520-6882

文摘

Adopting strict cleanroom procedures, ice samples fromthe Canadian High Arctic have been analyzed for Pbconcentrations and Pb isotopes (²⁰⁶Pb, ²⁰⁷Pb, ²⁰⁸Pb)using ICP-SMS. The detection limit for Pb (0.06 pg g^-1)was ~2 orders of magnitude lower than the lowestconcentration of Pb in the ice samples (range, 4.3-1660pg g^-1; median, 45 pg g^-1). Acidification of ice sampleswith high-purity HNO₃ for stabilization purposes contributed only 0.004 pg of Pb g^-1, which is an insignificantsource of Pb. Using a new sample introduction systemconsisting of a heated (140 C) minicyclonic spray chamber and a Peltier cooled condenser (2 C) and by replacingthe conventional sample cone with a high-performancecone, signal intensities for Pb were increased by ~1 orderof magnitude. Thus, it was possible not only to measurePb isotope ratios directly using ICP-SMS but also toachieve reasonable precision (~0.2%) at low picogram pergram concentrations of total Pb. This precision is comparable to that achievable by thermal ionization massspectrometry at such low Pb concentrations, but the ICP-SMS requires much less sample volume (~2 mL), needsno sample pretreatment, and therefore is considerablyfaster and less expensive than the conventional approach.Even though absolute Pb concentrations in two icesamples dating from 1974 and 1852 were very similar(9 and 6 pg g^-1) their fundamentally different isotopicsignature (²⁰⁶Pb/²⁰⁷Pb: 1.169 ± 0.002 vs 1.147 ±0.003) clearly indicates different sources of Pb. Theanalytical procedures described here, therefore, offergreat promise for fingerprinting the predominant sourcesof atmospheric Pb in polar snow and ice.