内标元素强度筛选法在激光诱导击穿光谱定量分析土壤标样中铁钛锶的应用
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摘要
利用激光诱导击穿光谱(LIBS)技术进行光谱定量分析时,由于实验条件不稳定造成的测量结果检出限高、测量精确度低的问题一直是一个亟待解决的难题。实验选取地质矿产部化探分析质量监控站的标准土壤样品为分析样品,以波长为1 064nm的Nd∶YAG激光器为激发光源,脉冲重复频率1Hz,通过激光诱导击穿光谱实验装置采集土壤样品在420~440nm范围内的等离子体光谱图。采用以内标法为基础的数据平均处理和内标元素强度筛选法(即以选定的内标元素谱线强度为参考,进行数据筛选)处理数据分别分析了待测样品中的Fe、Ti和Sr元素的含量并进行了对比,利用内标元素强度筛选法测得Fe、Ti和Sr的质量分数分别为68.4mg/g、10 777μg/g和75.5μg/g,相对误差由平均法测得的10.60%、3.20%和8.57%降低为2.01%、0.21%和1.95%。说明内标元素强度筛选法处理数据可以减少数据处理量,简化数据处理过程并提高分析精度,尤其适用于激光能量输出不稳定、时间延迟较难控制的实验条件下的物质成分定量分析。
During the quantitative analysis by laser induced breakdown spectroscopy(LIBS),the problem of high detection limit and low measurement precision due to the instability of experimental conditions was always a challenge to be solved.The soil standard sample from Quality Control Station of Ministry of Geology and Mineral Resources for geochemical analysis was selected as the test sample.The Nd∶YAG laser with wavelength of 1 064 nm was used as the excitation light source.The pulse repetition frequency was1 Hz.The plasma spectra of soil sample in range of 420-440 nm was collected using LIBS experimental device.The data average processing based on internal standard method and internal standard element intensity-screening method(i.e.,the spectral intensity of selected internal standard element was used as reference for data screening)were used for the analysis and comparison of Fe,Ti and Sr contents in test samples,respectively.The measured mass fraction of Fe,Ti and Sr by internal standard element intensityscreening method was 68.4 mg/g,10 777μg/g and 75.5μg/g,respectively.The relative error was reduced to 2.01%,0.21%and 1.95%from 10.60%,3.20%and 8.57% by average method,respectively.The results indicated that the internal standard element intensity-screening method could reduce the data processing capacity,simplify the data handling process and improve the analysis precision.Particularly,the proposed method was suitable for the quantitative analysis of composition under experimental conditions when the laser energy output was unstable and the time delay was hardly controlled.
During the quantitative analysis by laser induced breakdown spectroscopy(LIBS),the problem of high detection limit and low measurement precision due to the instability of experimental conditions was always a challenge to be solved.The soil standard sample from Quality Control Station of Ministry of Geology and Mineral Resources for geochemical analysis was selected as the test sample.The Nd∶YAG laser with wavelength of 1 064 nm was used as the excitation light source.The pulse repetition frequency was1 Hz.The plasma spectra of soil sample in range of 420-440 nm was collected using LIBS experimental device.The data average processing based on internal standard method and internal standard element intensity-screening method(i.e.,the spectral intensity of selected internal standard element was used as reference for data screening)were used for the analysis and comparison of Fe,Ti and Sr contents in test samples,respectively.The measured mass fraction of Fe,Ti and Sr by internal standard element intensityscreening method was 68.4 mg/g,10 777μg/g and 75.5μg/g,respectively.The relative error was reduced to 2.01%,0.21%and 1.95%from 10.60%,3.20%and 8.57% by average method,respectively.The results indicated that the internal standard element intensity-screening method could reduce the data processing capacity,simplify the data handling process and improve the analysis precision.Particularly,the proposed method was suitable for the quantitative analysis of composition under experimental conditions when the laser energy output was unstable and the time delay was hardly controlled.
引文
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[2]章婷婷,舒嵘,刘鹏希,等.远程激光诱导击穿光谱技术分析岩石元素成分[J].光谱学与光谱分析,2017,37(2):594-598.ZHANG Ting-ting,SHU Rong,LIU Peng-xi,et al.Element analysis of rock with remote laser induced breakdown spectroscopy[J].Spectroscopy and Spectral Analysis,2017,37(2):594-598.
[3]葛锦蔓,苏俊宏,徐均琪,等.激光诱导击穿光谱在薄膜损伤分析中的应用[J].光子学报,2016,45(4):0414004-1-0414004-6.GE Jin-man,SU Jun-hong,XU Jun-qi,et al.Application of laser-induced breakdown spectroscopy to analysis of thin-film damage[J].Acta Photonica Sinica,2016,45(4):0414004-1-0414004-6.
[4]张勇,许涛,刘英,等.发射光谱法对早期激光诱导铝合金等离子体诊断研究[J].光谱学与光谱分析,2017,37(7):2210-2215.ZHANG Yong,XU Tao,LIU Ying,et al.Early stage diagnostics for laser-induced aluminum alloy with optical emission spectroscopy[J].Spectroscopy and Spectral Analysis,2017,37(7):2210-2215.
[5]Fisher B T,Johnsen H A,Buckley S G,et al.Temporal gating for the optimization of laser-induced breakdown spectroscopy detection and analysis of toxic metals[J].Appl.Spectrose.,2001,55(10):1312-1319.
[6]周卫东,刘艳杰,黄基松.工作参数对激光诱导土壤等离子体光谱特性的影响[J].大气与环境光学学报,2016,11(5):361-365.ZHOU Wei-dong,LIU Yan-jie,HUANG Ji-song.Effect of parameters on spectrum characteristics of laser induced soil plasma[J].Journal of Atmospheric and Environmental Optics,2016,11(5):361-365.
[7]Jin Yu,Qianli Ma,V.m.Ros,et al.Generation and expansion of laser-induced plasma as a spectroscopic emission source[J].Front.Phys.,2012,7(6):649-669.
[8]赵书瑞,赵志巍,王华丽,等.激光频率对激光诱导等离子体特性的影响[J].冶金分析,2017,37(6):9-13.ZHAO Shu-rui,ZHAO Zhi-wei,WANG Hua-li,et al.The affection of the laser frequency on the laser-induced soil plasma[J].Metallurgical Analysis,2017,37(6):9-13.
[9]李百慧,高勋,宋超,等.磁空混合约束激光诱导Cu等离子体光谱特性[J].物理学报,2016,65(23):235201-1-235201-6.LI Bai-hui,GAO Xun,SONG Chao,et al.Laser induced plasma spectral characteristics of Cu with magnetically and spatially combined con nement[J].Acta Phys.Sin.,2016,65(23):235201-1-235201-6.
[10]Jose V.Pastor,Jose M.Garcia-oliver,Antonio Garcia,et al.Laser induced plasma methodology for ignition control in direct injection sprays[J].Energy Conversion and Managment,2016,86(4):144-156.
[11]Zong Hou,Zhe Wang,Lizhe Li,et al.Improving data stability and prediction accuracy in laser-induced breakdown spectroscopy by utilizing a combined atomic line algorithm[J].J.Anal.At.Spectrom.,2013,28(1):107-113.
[12]刘莉.双谱线内标对激光诱导击穿光谱稳定性的改善[J].激光技术,2015,39(1):90-95.LIU Li.Stability improvement of laser-induced breakdown spectroscopy based on dual-line intenral standard[J].Laser Technology,2015,39(1):90-95.
[13]张雷,马维光,闫晓娟,等.激光诱导等离子体光谱用于煤中氧的定量分析[J].量子光学学报,2011,17(1):70-76.ZHANG Lei,MA Wei-guang,YAN Xiao-juan,et al.Quantitative analysis of oxygen in coal by laser-induced plasma spectroscopy[J].Acta Sinica Quantum Optica,2011,17(1):70-76.