单变量分析方法与多变量分析方法结合激光诱导击穿光谱分析翡翠化学成分的对比

Comparison of Univariate and Multivariate Analysis for JadeiteUsing Laser Induced Breakdown Spectroscopy

  • 摘要: 激光诱导击穿光谱(LIBS)是一种原子光谱技术,可以同时快速分析多基质成分样品的化学元素组成,包括气体、液体和固体。然而,由于激光消融的不稳定性、基体效应以及自吸收等原因,LIBS的定量测量分析的能力一直没有得到公认。LIBS结合单变量分析方法与多变量分析方法可以快速分析多基质成分样品的化学元素含量,为了探究哪一种分析方法更适合LIBS定量测量分析翡翠,分别采用单变量和多变量的偏最小二乘法(PLS)分析翡翠样品的LIBS光谱数据并建立模型预测Ca和Al的含量。采用单变量建立模型时,对于Ca元素,校正模型与预测模型的相关系数分别为0.93和0.92,校正模型与预测模型的标准均方根误差分别为1.14和1.43;对于Al元素,校正模型与预测模型的相关系数分别为0.63和0.58,校正模型与预测模型的标准均方根误差分别为3.04和3.59。在建立多变量的偏最小二乘法模型时,使用波长197.33~762.8 nm范围的峰值强度与质量分数之间的拟合,对于Ca元素,校正模型与预测模型的相关系数分别为0.97和0.95,校正模型与预测模型的相标准均方根误差分别为0.81和1.08;对于Al元素,校正模型与预测模型的相关系数分别为0.92和0.89,校正模型与预测模型的标准均方根误差分别为1.36和1.79。结果显示偏最小二乘法能够提高LIBS对缅甸翡翠的定量测量分析。

     

    Abstract: Laser induced breakdown spectroscopy (LIBS) is an atom analysis technique which can be used for studying the element composition of multitudinous specimen matrices, including gas, liquid or solid.LIBS has demonstrated significant potential for the gemstone identification, with the capabilities of simultaneous multiple elements detection and rapid analysis.However, for the unstable ablation, matrix effect and self-absorption, there has been long controversy about its quantitative analytical capability.Univariate and multivariate analysis are the main means for LIBS to analyze and test element composition of multitudinous specimen matrices.Multivariate analytical techniques have great potential for analyzing the complicated LIBS spectra.In this paper, univariate and multivariate statistical analysis techniques were coupled with LIBS to identify different types of jadeite samples with various elemental composition concentrations.The authors employed the univariate and the partial least square (PLS) techniques to analyze the LIBS spectra of jadeite samples and built calibration models predicting Ca and Al concentrations.The results indicated that PLS could significantly improve the analytical results in comparison with the univariate technique.The normalized root mean square error (RMSE) and R2 of the univariate models were 1.14 and 0.93 in calibration and 1.43 and 0.92 in prediction for Ca, while 3.04 and 0.63 in calibration and 3.59 and 0.58 in prediction for Al.For the PLS models using the spectral range 197.33 to 762.8 nm, the RMSE and R2 are 0.81 and 0.97 for Ca, 1.08 and 0.95 for Al in calibration respectively, as well as 1.36 and 0.92 for Ca and 1.79 and 0.89 for Al in prediction respectively.The results showed that PLS could enhance the quantitative analytical capability of LIBS for jadeite analysis.

     

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