探索在内标物谱线选择受限情况下利用激光诱导击穿光谱(LIBS)技术进行定量分析的可行方案, 并应用到复杂钢铁合金中痕量金属元素钼(Mo)的检测分析中。 实验中烧蚀激光波长为532 nm, LIBS信号的采集通过光栅单色仪、 CCD、 Boxcar和PMT来完成。 对Mo的550.649, 553.305和557.045 nm三条原子谱线峰高值随Mo元素含量的改变进行分析, 利用双盲法检测分析一待测样品中所含Mo元素质量分数。 待测样品中Mo元素质量分数标定值为2.111%, 其中利用 Mo Ⅰ 550.649 nm谱线进行分析得待测样品中Mo元素质量分数为2.229%, 与标定值相对误差5.57%为最小; 利用 Mo Ⅰ 553.305 nm谱线分析结果次之; 由于 Mo Ⅰ 557.045 nm谱线发射强度较低且受到合金中Fe Ⅰ 556.9618 nm和Fe Ⅰ 557.2841 nm等元素谱线干扰, 所得Mo元素质量分数为2.346%, 与标定值相对误差11.15%为最大。 利用三条谱线的峰高值之和进行分析得Mo元素质量分数为2.271%, 与标定值相对误差为7.58%, 结果优于三条谱线分别定标结果的平均值。 可见, 采用上述三条Mo原子谱线峰高值之和进行定量分析或对三条谱线定标分析的结果取平均值, 可在一定程度上解决用单一谱线定标时由于选择受干扰谱线而引起的分析误差较大的问题。 本文还讨论了实验中保持样品有效烧蚀效率稳定性的方法。 结果表明, 在内标选择受限情况下, 保证实验条件一致性, 选择合理的分析谱线以及方案也可以得到较高定量分析精度。

The quantitative analysis using laser induced breakdown spectroscopy (LIBS), lack of appropriate interior label element, is described and applied to trace element molybdenum (Mo) detection in complex metallic alloys. A Q-switched Nd∶YAG laser operating at 532 nm was utilized to generate plasma and the emission was recorded by a grating spectrometer equipped with CCD, boxcar and PMT. The three peak heights of Mo Ⅰ, 550.649, 553.305 and 557.045 nm, changing with Mo mass fraction in metallic alloys were measured to produce calibration curves respectively, and double blind method was used to analyse a test sample. Based on Mo Ⅰ 550.649 nm line, the Mo mass fraction in the test sample was determined to be 2.229% with relative error of 5.57% in comparison with the given value of 2.111%. On using Mo Ⅰ 557.045 nm line, the relative error was found to be doubled due to the overlap with Fe emission lines. While taking the total height of three atomic lines into account in analysis, the resulted error dropped to 7.58%, even better than the average of predicted concentrations based on the above three lines. The obtained results demonstrate that satisfactory precision could be obtained under a consistent experiment condition with the above scheme, even without appropriate interior label element. The methods of maintaining stable laser ablation efficiency on sample are also discussed.