高纯金属纯度测量研究

Determination of the Total Purity of High Purity Metals

高纯金属作为先进材料和化学成分量溯源的基础原料,其杂质和纯度量值是重要指标。全杂质元素扣除,即扣除包括非金属和气体元素等杂质的纯度测量方法已成为高纯金属纯度定值的权威方法。该文以高纯金纯度标准物质(GBW02793)为例,详细介绍了辉光放电质谱法、高分辨电感耦合等离子体质谱法、燃烧红外法和惰气熔融-红外热导法等多种方法在纯度测量中的研究要点。对引起辉光放电质谱测量偏差的重要因素—相对灵敏度因子进行了修正,将测量不确定度从200%降至30%。分别采用辉光放电质谱法和高分辨电感耦合等离子体质谱法两种方法对高含量的金属杂质元素Na、Fe、Cu进行测量,方法结果一致。痕量气体元素H、C、N、S采用惰气熔融-红外热导法和燃烧红外法进行测量,其含量分别为0.35、0.51、0.45、0.85 mg/kg,均低于定量下限。采用惰气熔融-红外热导法和二次离子质谱法对痕量氧含量进行了测量,两种方法结果相近。同时对惰性气体元素和放射性元素含量进行了合理评估,并对纯度测量不确定度进行了评定。最终得到扣除94种杂质元素的高纯金标准物质中金的质量分数为99.9995%,扩展不确定度为0.0002%。

As fundamental materials of advanced materials and chemical metrological traceability,high purity metals play an important role.The impurity and purity values are important indicators of them.The total purity analysis,means deducting all elemental impurities including non-metals and gas elements,has become an authoritative method for determining the purity of high purity metals.With high purity gold certified reference material(GBW02793)as an example,this paper described in detail the research points of various methods in total purity analysis,including glow discharge mass spectrometry,high resolution inductively coupled plasma mass spectrometry,combustion infra⁃red absorption and inert gas fusion infrared absorption methods.A systematic correction has been made to the relative sensitivity factor,which is an important factor causing measurement bias in glow discharge mass spectrometry method,reducing the measurement uncertainty from 200%to 30%.High mass fraction of metallic elemental impurities Na,Fe and Cu were measured by using glow dis⁃charge mass spectrometry and high resolution inductively coupled plasma mass spectrometry.Both re⁃sults were agreed with each other.Trace gas elements H,C,N,and S were detected by combustion infrared absorption method and inert gas fusion infrared absorption method.And all of them were low⁃er than the limits of quantitative,which were 0.35 mg/kg,0.51 mg/kg,0.45 mg/kg,and 0.85 mg/kg,respectively.Trace oxygen was measured by using inert gas fusion infrared absorption method and secondary ion mass spectrometry.Two measurement results were close.A reasonable evaluation was conducted on the mass fractions of inert gas elements and radioactive elements,and the uncer⁃tainty of gold purity was evaluated.Finally,the determination method of total purity of high purity gold was established.The mass fraction of gold in high purity gold certified reference material was 99.9995%and the extended uncertainty was 0.0002%.