蒸汽加热消解-电感耦合等离子体质谱法测定化探样品中痕量金

将样品焙烧后采用蒸汽加热王水消解,用两块聚氨酯泡塑分两次吸附消解后样品溶液中的痕量Au,将两块泡塑合并、灰化,用王水溶解,以Re为内标进行校正,实现了采用电感耦合等离子体质谱法(ICP-MS)对化探样品中痕量Au的测定。对消解条件、吸附条件和脱附条件进行了优化,结果表明:采用蒸汽加热消解所得到的Au测定结果与电热板消解相同,但蒸汽加热消解方法能够明显节约电力能源并能有效降低外来污染;选用化探金标准物质为试验对象,在吸附时间相同的条件下,分两次投入2块泡塑进行吸附,Au的回收率为97%~101%,比一次投入2块泡塑的Au回收率87%~92%更接近100%;采用先在180℃灰化20min,再经50min升温至700℃灰化1h的方法对载Au泡塑进行灰化,化探金标准物质中Au的回收率稳定在100%附近。在选定的实验条件下,校准曲线的线性相关系数为0.9996,方法检出限为0.13ng/g,测定下限为0.43ng/g,测定上限为120ng/g。应用实验方法对3件化探金标准物质、3件土壤样品和3件水系沉积物样品中Au进行了测定,结果表明:化探金标准物质的测定值与认定值相符;Au测定值的相对标准偏差(RSD,n=12)为2.9%~6.4%。按照实验方法对化探金标准物质进行加标回收试验,回收率为98%~104%。

Determination of trace gold in geochemical sample by inductively coupled plasma mass spectrometry with steam heating digestion

After the sample was roasted and digested in aqua regia by steam heating. The trace gold in sample solution after digestion was adsorbed for twice with two pieces of polyurethane foam plastics. The foam plastics were merged and ashed followed by dissolution with aqua regia. The internal standard Re was selected for correction. Thus, a determination method of trace gold in geochemical sample by inductively coupled plasma mass spectrometry (ICP-MS) was established. The conditions of digestion, adsorption and desorption were optimized. The results showed that when the sample was digested by steam heating, the determination results of gold were the same as those obtained by electric heating plate digestion. However, the steam heating digestion could save electrical energy and effectively reduce the external pollution. The certified reference materials of geochemical gold were selected for comparison tests. Two pieces of foam plastics were used for absorption in twice with absorption time keep the same. The recoveries of gold were between 97% and 101%, which were more close to 100% compared to those obtained by two pieces of foam plastics for once absorption (i.e., 87%-92%). The gold-loaded foam plastics were firstly ashsed at 180℃ for 20min. Then the temperature was increased to 700℃ within 50min and the foam plastics were further ashed for 1h. The recoveries of gold in certified reference materials of geochemical gold were stable near 100%. Under the selected experimental conditions, the linear correlation coefficient of calibration curve was 0.9996. The detection limit of method was 0.13ng/g. The lower and upper determination limit was 0.43ng/g and 120ng/g, respectively. The proposed method was applied for the determination of gold in three certified reference materials of geochemical gold, three soil samples and three stream sediments. It was found that the results of certified reference materials of geochemical gold were consistent with the certified values. The relative standard deviations (RSD, n=12) of the determination results of gold were between 2.9% and 6.4%. The recovery test of standard addition was conducted according to the experimental method with certified reference materials of geochemical gold. The recoveries were between 98% and 104%.