Istituto Nazionale di Ricerca Metrologica (INRIM) , Strada delle Cacce 91, 10135 Torino, Italy.
Department of Chemistry, University of Pavia , via Taramelli 12, 27100 Pavia, Italy.
Anal Chem. 2017 Jun 20;89(12):6726-6730. doi: 10.1021/acs.analchem.7b00963. Epub 2017 Jun 8.
The use of new silicon single crystals highly enriched in Si recently produced for the upcoming redetermination of the Avogadro constant requires knowledge of their molar masses. The isotopic composition data are collected independently in different laboratories but all using the virtual element technique with multicollector inductively coupled plasma mass spectrometers. In this framework, the comparison of the results with an independent measurement of the amount of at least one of the depleted isotopes is useful to limit hidden systematic errors. To this aim, the Si mole fraction of a sample of the new material was measured using a relative measurement protocol based on instrumental neutron activation analysis. The protocol is similar to that previously applied with the AVO28 silicon material used for the last determination of the Avogadro constant value with the exception that unknown and standard samples are not coirradiated. The x(Si) = 5.701 × 10 mol mol estimate is close to the expected one and is given with a standard uncertainty of 8.8 × 10 mol mol. This value, if adopted, gives a contribution to the relative standard uncertainty of the Avogadro constant of 6.3 × 10.
新的硅单晶，其硅的同位素丰度极高，最近被用于即将进行的阿伏伽德罗常数重新测定，这需要知道它们的摩尔质量。同位素组成数据是在不同的实验室中独立收集的，但都使用带有多接收电感耦合等离子体质谱仪的虚拟元素技术。在这种情况下，将结果与对至少一种耗尽同位素的量的独立测量进行比较，有助于限制隐藏的系统误差。为此，使用基于仪器中子活化分析的相对测量方案，对新材料的样品中的 Si 摩尔分数进行了测量。该方案与之前在 AVO28 硅材料中应用的方案相似，不同之处在于标准和未知样品不是同辐照的。x(Si) = 5.701 × 10 mol/mol 的估计值接近预期值，并给出了 8.8 × 10 mol/mol 的标准不确定度。如果采用这个值，将对阿伏伽德罗常数的相对标准不确定度贡献 6.3 × 10。
