银保护灰吹铅试金-高分辨率连续光源火焰原子吸收光谱法测定铁粉中痕量金

铁粉是提取Au的重要原料,故需准确测定铁粉中的Au。采用自制并提纯的碱式碳酸铅作为捕集剂熔融得到铅扣,经加银保护灰吹铅扣将Au进一步富集在银合粒中,压制银合粒成片,采用先加入HNO₃加热溶解,再加入HCl加热溶解的方式溶解银片,使Au完全溶解进入溶液,选择像素点为5,采用高分辨率连续光源火焰原子吸收光谱法(HR-CS-FAAS)进行分析,实现了对铁粉样品中Au的测定。实验比较了王水加热溶解-聚氨酯泡沫塑料富集分离和加Ag保护灰吹铅试金法两种样品处理方法。结果表明,采用王水加热溶解样品不能将样品溶解完全,且Au的测定结果相比加Ag保护灰吹铅试金法显著偏低,而采用铅试金法处理样品,样品熔融状态较好、熔渣流动性好,可使Au完全富集在铅扣中。对银合粒的溶解方法进行了试验,结果表明,采用加HNO₃加热溶解后再加HCl的分步加热溶解方式可将银合粒溶解完全。共存离子干扰试验表明,样品中的共存离子不干扰测定。在选定的优化实验条件下,Au的吸光度与其对应的质量浓度运用二次方程最小二乘法拟合校准曲线,校准曲线决定系数为0.999 9;方法检出限为0.005 25 μg/g,定量限为0.017 32 μg/g。将所建立的方法应用于实际铁粉样品中0.56~12.6 μg/g Au的测定,结果的相对标准偏差(n=6)为2.3%～3.7%,加标回收率为92%～107%,满足国家地质矿产行业标准DZ/T 0130—2006对于回收率的要求。

Determination of trace gold in iron powder by high resolution continuum source flame atomic absorption spectrometry with silver protection cupellation lead fire assay enrichment

Iron powder is an important raw material for Au extraction, so it is necessary to accurately determine Au in iron powder. The self-prepared and purified basic lead carbonate was used as collector to obtain lead button by melting. Through silver protection cupellation, Au was further enriched in the silver particles. The silver particles were pressed to sheet and dissolved with HNO₃ by heating. Then, the silver sheet was dissolved by adding HCl and heating. Au was fully dissolved and entered the solution. The solution was determined by high resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS) by selecting the pixel of 5. Consequently, the determination of Au in iron powder sample was realized. Two kinds of sample treatment methods, i.e., aqua regia heating-polyurethane foam adsorption separation enrichment and Ag protection cupellation lead fire assay, were compared in experiments. The results showed that the samples could not be completely dissolved by heating with aqua regia, and the determination results of Au was significantly lower than that of Ag protection cupellation lead fire assay. When the sample was treated by lead fire assay, the melting state of sample was good, and the fluidity of melting slag was also good. Au could be fully enriched in lead button. The dissolution method of Ag granule was investigated. The results showed that the Ag granule could be fully dissolved via HNO₃ heating followed by HCl heating in sequence. The interference test of coexistence ions indicated that the coexistence ions did not interfere with the determination. Under the selected optimal conditions, the absorbance of Au and the corresponding mass concentration were fitted with least square method of quadratic equation to obtain the calibration curve. The linearity of the calibration curve was good, and the determination coefficient was 0.999 9. The limit of detection of method was 0.005 25 μg/g, and the limit of quantification was 0.017 32 μg/g. The proposed method was applied for the determination of actual iron powder sampled with Au content of 0.56-12.6 μg/g. The relative standard deviations (RSD, n=6) were between 2.3% and 3.7%. The spiked recoveries were between 92% and 107%, which could meet the requirement of recovery rate in national geological and mineral industry standard DZ/T 0130-2006.