高纯铪由于具有独特的理化性质, 在核反应堆、 等离子切割机、 光学元件等方面有着重要的应用。 高纯铪中杂质的种类和含量会影响高纯铪的物理化学性能, 应用中对高纯铪纯度的要求也越来越高, 这就对高纯铪的分析检测技术提出了更高的要求。 激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS)是激光剥蚀进样技术与电感耦合等离子体质谱联用,可以直接分析固体样品,并且方法前处理简单,可以避免样品前处理过程中引入杂质, 是一项高效、 快速、 精密的分析技术, 在环境、 地质、 冶金、 燃料能源、 材料、 生物医药、 考古等领域广泛应用。 所以, 激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS)是高纯金属杂质元素最佳检测方法之一。 还未见有应用LA-ICP-MS于高纯铪样品的报道。 用LA-ICP-MS对高纯铪中10种杂质元素(Al,Sc,Ti,Fe, Ni, Cu, Mo, Ag, Sn, W)进行定量分析。 为了降低激光剥蚀过程中元素的分馏效应, 提高信号灵敏度和稳定度, 对激光剥蚀参数进行优化实验。 确定了激光剥蚀的最优仪器参数为: 氦气流量600 mL·min^-1, 激光能量90%, 剥蚀孔径150 μm, 激光扫描速度60 μm·s^-1, 激光脉冲频率20 Hz。 经实验优化后的ICP-MS仪器工作参数为: RF功率1 450 W, 射频匹配电压1.8 V, 载气流量0.85 L·min^-1, 冷却器流量0.85 L·min^-1, 采样深度7.5 mm。 在最优参数条件下, 利用内控标样建立工作曲线, 各杂质元素标准曲线的线性相关系数为0.993 6~0.999 8。 采集载气空白的信号强度, 平行测定11次, 以3倍空白信号的标准偏差所对应的含量作为元素的检出限, 得到各元素的检出限为0.001~0.08 μg·g^-1。 将高纯铪制成尺寸合适的样品, 用硝酸洗去样品表面的氧化物, 将其装入剥蚀池中, 运用线扫描剥蚀方式, 在最佳仪器工作条件下, 对三个高纯铪样品中的10种杂质元素进行定量分析。 实验结果显示, 杂质元素含量为0.17~36.76 μg·g^-1, 相对标准偏差为1.4%~20%, 精密度良好。 以¹⁸⁴W为例, 将LA-ICP-MS法和ICP-MS法的测定结果进行t检验, 三个样品的 t值分别为2.14, 1.64和2.11, 均小于显著性水平为0.05时的临界值( t_{0.05, 12}=2.18), 说明LA-ICP-MS法和ICP-MS法的测定结果在置信度为95%时没有显著性差异, 即正确度良好。 所以, 该方法正确度和精密度良好, 可用于高纯铪中杂质的定量分析。

High purified hafnium has important applications in nuclear reactor, plasma cutting machine, optical element and so on, because of its unique physical and chemical properties. The type and content of impurities in high purity hafnium affect the physical and chemical properties of high purity hafnium, and the purity requirement of high-purity hafnium is also higher and higher. This requires higher requirements for the analysis and detection technology of high-purity hafnium. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a combination of laser ablation sampling technique and inductively coupled plasma mass spectrometry. The advantage of this method is that impurities can be avoided in the preprocessing,and the solid sample can be analyzed directly. So,this method is an efficient,fast and precise analytical technology, widely applied in the fields of environment, geology, metallurgy, fuel energy, materials, biomedicine, archaeology and so on. However, the application of testing high purity hafnium by LA-ICP-MS has not been reported while LA-ICP-MS is one of the best methods for the detection of high purity metallic impurities. Ten kinds of impurities (Al, Sc, Ti, Fe, Ni, Cu, Mo, Ag, Sn, W) in high purified hafnium were quantitatively analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In order to reduce the fractionation effect of elements in the laser ablation process and improve the signal sensitivity and stability, the laser denudation parameters were optimized. Experiments showed that the optimal laser ablation parameters were that He flow rate was 600 mL·min^-1, energy 90%, spot size 150 μm, scan rate 60 μm·s^-1and pulse repetition 20 Hz. The working parameters of ICP-MS instrument after experimental optimization were that RF power was 1 450 W, RF matching voltage 1.8 V, carrier gas flow rate 0.85 L·min^-1, cooling gas flow rate 0.85 L·min^-1, sample depth 7.5 mm. Under the best experimental conditions, internal control standard samples were used to establish working curves; the linear correlation coefficients of impurities were between 0.993 6 and 0.999 8. The signal intensity of the blank carrier gas was collected and measured for 11 times. The content of the standard deviation of the 3 times blank signal was taken as the detection limit of the elements. The detection limits of each element were from 0.001 to 0.08 μg·g^-1. High purified hafnium was made into a suitable sample of size. The oxide on the surface of the sample was washed with nitric acid. The sample was loaded into ablation pool, and laser ablated by line scanning. Under the best experimental conditions, ten kinds of impurities in three high purified hafnium samples were determined by LA-ICP-MS. The content of impurity elements was 0.17~36.76 μg·g^-1. Relative standard deviations were from 1.4% to 20%, which showed that the method has good precision. In the case of W, Student’s t test was made between the determination of LA-ICP-MS and ICP-MS. Student’s t test shows that the t values of the three samples were 2.14, 1.64 and 2.11, which were lower than the critical value of the significant level of 0.05 ( t_{0.05, 12}=2.18), so there was no significant difference between the results of LA-ICP-MS method and ICP-MS method. The trueness and precision were favorable, which showed that this method can be used for quantitative analysis of impurities in high pure hafnium.