基于内标法分析土壤中Pb元素的LIBS试验研究

Quantitative Analysis of Pb in Soil Using LIBS and Internal Standard Method

采用激光诱导击穿光谱技术(LIBS,laser induced breakdown spectroscopy)检测土壤样品的重金属元素,光谱仪探测等离子体发射信号,测量并分析了激光能量对土壤中Pb元素的等离子体特性的影响,结果表明激光能量为60mJ时信背比(SBR)最佳。为了减小误差,采用Lorenizian函数进行光谱轮廓曲线拟合数据预处理,提取光谱净强度值。选取土壤样品中的基体元素Fe作为内标元素,以PbI 405.78nm为分析线、FeI 406.35nm作为内标线,分别根据Pb元素的谱线强度、分析线与内标线强度比建立不同的定标曲线,两种定标曲线的拟合度R2分别为0.879、0.970。实验结果表明,内标法强度比能有效提高定标曲线的拟合度,减少定量分析误差,提高准确度。

At atmospheric pressure,soil samples were excited by pulse laser and plasma was formed. Laser induced breakdown spectroscopy（LIBS） was applied to measure heavy metal content ,was collected by fiber spectrometer. The influence of the la ser energy are measured and analyzed on Pb plasma characteristics in the soil. The experimental results showed that the signal to-background ratio（SBR） is best when the laser energy is 60mJ. To reduce the error, Lorenizian function is used to carry out the pre-processing of the data of spectral profile curve fitting, and extract spectral intensity values. The matrix element Fe was selected as internal standard,and with the spectral line of PbI 405.78nm as analysis line, the spectral line of FeI 406.35nm as internal line. Calibration curves were drawn respectively using the peak intensity of lead line and the intensity ratio of lead line and Iron line. The fitting degree of two different calibration curves（R2） are 0. 879 and 0.97. The results of the analysis show that internal standard method seems more adequate than the peak intensity method for establishing the calibration cures.