激光诱导击穿光谱分析土壤样品中的锆、铪和铌元素含量实验研究

锆、铪和铌是多目标地球化学样品分析的重要元素，传统的湿法前处理很难将这些高场强元素完全消解，致使测定的结果偏低，且传统的湿法有消解用酸、碱量大，前处理流程长，污染环境等缺点。激光诱导击穿光谱（LIBS）在分析地球化学样品时有独特的优势，尤其是对于那些常规条件下消解不完全的元素。采用激光诱导击穿光谱对土壤样品中的锆、铪和铌元素进行定量分析，首先对激光的输出能量，光谱仪采集延迟时间以及激光器的光斑直径等实验条件进行优化。对比激光输出能量从0.0～4.4 mJ的测定土壤样品中的锆、铪和铌元素的准确度，当选用1.6 mJ时，可得到最佳的实验结果。其次分析光谱仪采集延迟时间对测定土壤样品中的锆、铪和铌元素的影响，结果显示0.5 μs是最佳的采集延迟时间。最后，对比激光不同的光斑直径得到测定结果，发现50 μm的光斑直径测定稳定性最好。还对测定模式和样品制备压力进行了对比研究，结果表明利用激光诱导击穿光谱对土壤样品中锆、铪和铌测量时在制样压力2 000 kN，采用动态模式，LIBS信号的稳定性和定量分析的精确度都是最好的。在最佳的实验条件（激光输出能量1.6mJ、光谱仪采集延长时间0.5 μs和激光光斑直径50 μm）和制样压力2 000 kN采用动态模式对9个国家一级标准物质中的锆、铪和铌元素进行光谱检测，其测定值与推荐值基本吻合，3个国家一级标准物质精密度不超过11%，能满足地球化学样品的分析要求。综上，建立了激光诱导击穿光谱分析土壤样品中的锆、铪和铌元素含量的方法，解决了锆、铪和铌元素湿法消解不能完全消解和测定结果偏低的问题，具有分析效率高，操作简单，无污染，同时也为固体进样技术的发展提供了参考。

Determinations of Zr,Hf and Nb Contents in Soil Samples by Laser-Induced Breakdown Spectroscopy (LIBS)

Zirconium, hafnium and niobium are important elements in analysing multi-objective geochemical samples. It is difficult to completely remove these high field strength elements in traditional wet pretreatment, resulting in low results. Moreover, traditional wet digestion has many disadvantages, such as high acid and alkali, long pretreatment process and environmental pollution. LIBS has a unique advantage in analysing geochemical samples, especially for those elements that are not completely digested under conventional conditions. In this study, the zirconium, hafnium and niobium elements in soil samples were quantitatively analyzed by laser-induced breakdown spectroscopy. Firstly, the output energy of the laser, the longer time of acquisition by the spectrometer and the diameter of the laser spot were optimized. Comparing the accuracy of the laser output energy from 0.0 to 4.4 mJ in determining zirconium, hafnium and niobium in soil samples, when 1.6mj is selected, the best experimental results can be obtained. Secondly, the influence of the extended collection time of the spectrometer on the determination of zirconium, hafnium and niobium in soil samples is analyzed, and the results show that 0.5 μs is the best acquisition delay time condition. Finally, the measurement results are obtained by comparing different laser spot diameters, and 50 μm is selected, the stability of the measurement is the best. At the same time, this experiment also carried out a comparative experimental study from the measurement mode and sample preparation pressure. The results show that the stability of the LIBS signal and the accuracy of quantitative analysis is the best when using laser-induced breakdown spectroscopy to measure Zr, Hf and Nb in soil samples under the sample preparation pressure of 2 000 kN and dynamic mode. Under the optimal experimental conditions (laser output energy 1.6 mJ, spectrometer acquisition time 0.5 ms and laser spot diameter 50 μ m). The dynamic model was used to detect Zr, Hf and Nb in 9 national first-class reference materials. The measured values are consistent with the recommended values. The precision of 3 national first-class reference materials is less than 11%, which can meet the analysis requirements of geochemical samples. Based on the above conditions, this paper established a laser-induced breakdown spectroscopy (LIBS) method to analyze the content of Zr, Hf and Nb in soil samples, which solved the problems of incomplete digestion and low determination results of Zr, Hf and Nb in wet digestion. It has high analysis efficiency, simple operation and no pollution. It also provides a choice for the development of solid sampling technology.