Institute for National Measurement Standards, National Research Council Canada, Ottawa, Ontario K1A 0R6, Canada.
Anal Chem. 2012 Mar 6;84(5):2321-7. doi: 10.1021/ac203006j. Epub 2012 Feb 9.
The much anticipated overhaul of the International System of Units (SI) will result in new definitions of base units in terms of fundamental constants. However, redefinition of the kilogram in terms of the Planck constant (h) cannot proceed without consistency between the Avogadro and Planck constants, which are both related through the Rydberg constant. In this work, an independent assessment of the atomic weight of silicon in a highly enriched (28)Si crystal supplied by the International Avogadro Coordination (IAC) was performed. This recent analytical approach, based on dissolution with NaOH and its isotopic characterization by multicollector inductively coupled plasma mass spectrometry, is critically evaluated. The resultant atomic weight A(r)(Si) = 27.976 968 39(24)(k=1) differs significantly from the most recent value of A(r)(Si) = 27.976 970 27(23)(k=1). Using the results generated herein for A(r)(Si) along with other IAC measurement results for mass, volume, and the lattice spacing, the estimate of the Avogadro constant becomes N(A) = 6.022 140 40(19) × 10(23) mol(-1).
国际单位制（SI）的全面修订将导致基本单位根据基本常数重新定义。然而，如果阿伏伽德罗常数和普朗克常数之间不一致，就无法根据普朗克常数（h）重新定义千克，这两个常数都通过里德伯常数相关联。在这项工作中，对国际阿伏伽德罗协调组织（IAC）提供的高浓度（28）Si 晶体中的硅的原子量进行了独立评估。这种基于 NaOH 溶解及其同位素通过多接收电感耦合等离子体质谱进行特征化的最新分析方法受到了严格评估。得到的原子量 A(r)(Si) = 27.976 968 39(24)(k=1)与最近的 A(r)(Si) = 27.976 970 27(23)(k=1)值有显著差异。使用本文生成的 A(r)(Si)结果以及 IAC 对质量、体积和晶格间距的其他测量结果，阿伏伽德罗常数的估计值变为 N(A) = 6.022 140 40(19) × 10(23) mol(-1)。
