在采用全杂质元素扣除法进行纯度计算时, 痕量氧对高纯金的纯度测定具有明显影响, 而以往的杂质扣除法不计算氧等非金属元素, 使得纯度测定结果缺乏说服力。 通过建立惰气熔融红外吸收法, 测量高纯金纯度标准物质中痕量氧含量, 同时采用二次离子质谱法进行了方法比对, 确保测量结果的可靠性。 优化了氧氮氢分析仪的测量参数, 确定了最佳工作条件: 吹扫时间35 s, 分析延迟75 s, 排气周期2, 排气时间25 s, 排气功率4 500 W, 分析功率4 000 W; 选择金属锡作为助熔剂, 通过氧释放实验确定金锡比为5∶3, 对金样品进行二次测量发现氧残留与空白一致, 说明锡粒的加入可以促进金中氧的释放, 从而解决了金中氧释放不完全的难题; 对锡粒进行反复脱氧, 降低空白, 获得了稳定的测量空白, 方法定量限达到0.1 mg·kg^-1; 采用碳酸钠纯度标准物质对氧氮氢分析仪进行了校正, 校正系数为1.012, 同时氧的加标回收率在95%~105%之间, 验证了测量方法的可靠性并保证了测量结果的溯源性。 将高纯金制备成树脂靶件, 在二次离子质谱仪中以Cs⁺作为一次离子源, 光阑400 μm, 离子束强度为3 nA, 束斑大小约20 μm, 栅格扫描大小为10 μm, 二次离子光路光阑为400 μm, 质量分辨率约为2 400, 经过溅射和电离, 采集¹⁶O^-和¹⁸O^-离子流, 以SRM685高纯金标准物质作为测量标准, 通过标准、 样品的循环测量, 以标准和样品的离子强度对比计算含氧量。 采用两种方法的测量结果分别为(1.1±0.3)和(0.9±0.3) mg·kg^-1, 两个结果在不确定度范围内一致, 对测量不确定度的评定表明其主要来源为测量重复性, 最终确定高纯金纯度标准物质中痕量氧含量为(1.0±0.4) mg·kg^-1。 测量方法的建立实现了高纯金中痕量氧的准确测定, 为痕量氧测量和高纯金及其他高纯金属纯度标准物质的研制提供了有效的技术手段。

Trace oxygen has a noticeable influence on the purity assessment of high purity gold when the total elemental impurities deduction method was used to calculate the purity. However, the previous elemental impurities deduction method did not calculate the non-metallic elements such as oxygen, making the purity assessment not persuasive. The inert gas fusion infrared absorption method was established to measure the content of trace oxygen in high purity gold reference materials. The secondary ion mass spectrometry was used to compare the methods to ensure the reliability of the measurement results. The measurement parameters of the ONH analyzer were optimized, and the optimal working conditions were confirmed as follows: purge time 35 s, analysis delay 75 s, exhaust cycle 2, exhaust time 25 s, exhaust power 4 500 W, analysis power 4 000 W. Tin was selected as the flux, and the ratio of gold to tin was determined to be 5∶3 by oxygen release experiment. The secondary measurement of the gold sample showed that the residual oxygen was consistent with the blank, indicating that the addition of tin particles could promote the release of oxygen in gold, thus solving the problem of incomplete release of oxygen in gold. The tiny particles were deoxidized repeatedly to reduce the blank, and a stable blank was obtained. The limit of quantitation of the method reached 0.1 mg·kg^-1. The calibration coefficient is 1.012, and the recoveries of oxygen are between 95% and 105%, which verifies the reliability of the measurement method and ensures the traceability of the measurement results. In the secondary ion mass spectrometer, Cs⁺ is used as the primary ion source, the aperture is 400 μm, the ion beam intensity is 3 nA, the beam spot size is about 20 μm, the grid scanning size is 10 μm, and the secondary ion aperture is 400 μm. After sputtering and ionization,¹⁶O^- and¹⁸O^- ion currents were collected. SRM685 high purity gold reference material was used as the measurement standard. The oxygen content was calculated through the cyclic measurement of the standard and sample by comparing the ion current intensities between standard and sample. The results of the two methods were (1.1±0.3) and (0.9±0.3) mg·kg^-1 respectively. The uncertainty evaluation showed that the primary sources were the certified reference materials and measurement repeatability. The two results were consistent within the uncertainty range. Finally, the trace oxygen content in the high-purity gold reference material was (1.0±0.4) mg·kg^-1. The accurate determination of trace oxygen in high purity gold was realized by the two established measurement methods, which provide effective methods for the determination of trace oxygen and the development of high purity gold and other high purity metal certified reference materials.