聚氨酯泡沫塑料吸附-电感耦合等离子体质谱法测定地质化探样品中金

由于地质化探样品中金的品位较低,需将金分离富集后再进行测定。实验将样品经650 ℃高温灼烧后以王水(1+1)溶解,加入溴水以确保金全部被氧化为金,采用经20 g/L氢氧化钠-10%丙酮溶液处理过的聚氨酯泡沫塑料吸附金后于700 ℃灼烧灰化,用王水(1+1)溶解灰分,以5.0 ng/mL¹⁸⁵Re为内标,实现了电感耦合等离子体质谱法(ICP-MS)对地质化探样品中金的测定。实验表明:用取样器加入1.0 mL饱和溴水进行氧化,控制吸附体积约为100 mL,加入泡沫塑料后振荡吸附35 min,金的吸附率可达到98.9%。金在1～10 μg/mL质量浓度范围内与其对应的信号强度呈线性关系,相关系数为0.999 4,方法检出限为0.12 ng/g。采用实验方法对铂族元素地球化学成分分析标准物质、金矿石标准物质、化探金标准物质中金进行测定,测得结果与认定值的相对误差(RE)小于9%,相对标准偏差(RSD,n=12)小于10%。

Determination of gold in geochemical samples by inductively coupled plasma mass spectrometry with polyurethane foam plastic absorption

The content of gold in geochemical sample was relatively low and it should be separated and enriched before determination. The sample was burned at 650 ℃ followed by dissolution with aqua regia (1+1). The bromine water was added to make sure that all of gold was oxidized to gold(III). Then, gold(III) was adsorbed with polyurethane foam plastic which was pretreated by 20 g/L NaOH-10% acetone solution. After burning at 700 ℃, the ash was dissolved with aqua regia(1+1). Finally, the content of gold in geochemical sample was determined by inductively coupled plasma mass spectrometry (ICP-MS) with 5.0 ng/mL ¹⁸⁵Re as internal standard. The results showed that the adsorption rate of gold was up to 98.9% under the following experimental conditions: 1.0 mL of saturated bromine water was added with sampling device for oxidization of gold; the adsorption volume was controlled at about 100 mL; the oscillation adsorption time after adding polyurethane foam plastic was 35 min. The mass concentration of gold in range of 1-10 μg/mL was linear to the corresponding signal intensity with correlation coefficient of 0.999 4. The detection limit of method was 0.12 ng/g. The proposed method was applied to the determination of gold in certified reference materials for geochemical component analysis of platinum family elements, gold ore and geochemical gold. The relative errors (RE) between the results and the certified values were less than 9%. The relative standard deviations (RSD, n=12) were less than 10%.