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首页> 外文期刊>Spectrochimica Acta, Part B. Atomic Spectroscopy >Reduction of spectral interferences and noise effects in laser ablation molecular isotopic spectrometry with partial least square regression - a computer simulation study
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Reduction of spectral interferences and noise effects in laser ablation molecular isotopic spectrometry with partial least square regression - a computer simulation study

机译：偏最小二乘回归减少激光烧蚀分子同位素光谱中的光谱干扰和噪声影响-计算机模拟研究

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The fundamental analytical accuracies and precisions attainable by laser ablation molecular isotopic spectrometry (LAMIS), with emphasis on the impacts from spectral interferences and measurement noise, were investigated by means of computer simulation. The study focused on the analysis of a minor isotope at sub- to single-percentage abundance level. With a natural abundance about 1.1% for C-13, the C-2 Swan band (d 3 Pi(g-a) (3)Pi(u)) with Delta v = +1 was selected as a representative system. The characteristics (e.g., noise amplitude and distribution, signal strength, and signal-to-background ratio) of the simulated spectra were experimentally characterized. Partial least square (PLS) regression was used to extract isotopic information from the simulated molecular spectra. In the absence of any spectral interference and with the use of a calibration set consisting of eleven isotopic standards, the theoretical accuracies and precisions with signal accumulation from 100 laser shots are about 0.002% and 0.001%, respectively, in absolute percentage abundance of C-13. The theoretical analytical accuracies slightly degrade, but are adequate for many applications, to 0.004% and 0.008% respectively, for calibrations involving only three and two isotopic standards. It was found that PLS regression is not only immune to both source-flicker and photon-shot noise, but is also effective in differentiating the spectral patterns from the analyte against those from spectral interferences. The influences of spectral interference from single or multiple atomic emission lines were simulated, and new ways to minimize their impacts were formulated and demonstrated. It was found that the wavelength range selected for the computation of the normalization factor should not contain any spectral-interfering peak, and a properly chosen wavelength range increases the tolerance of spectral interference by at least one order of magnitude. With matrix-matched calibration standards, the precisions (expressed as RSDs of the determined C-13 isotopic abundances) degrade from similar to 1 parts per thousand in the absence of spectral interference, to similar to 3 parts per thousand, 10 parts per thousand and 20 parts per thousand with multiple spectral-interfering peaks that are 10x, 100x and 1000x, respectively, stronger than the molecular bandhead of the analyte. The study concluded that PIS regression is a powerful and indispensable tool for extraction of isotopic information from LAMIS spectra. (C) 2016 Elsevier B.V. All rights reserved.
机译：通过计算机模拟研究了激光烧蚀分子同位素光谱法（LAMIS）可获得的基本分析精度和精度，重点是光谱干扰和测量噪声的影响。该研究的重点是在亚百分比至单百分比丰度水平上分析次要同位素。由于C-13的自然丰度约为1.1％，因此选择了Delta v = +1的C-2​​天鹅带（d 3 Pi（g-a）（3）Pi（u））作为代表系统。实验地表征了模拟光谱的特征（例如，噪声幅度和分布，信号强度和信噪比）。使用偏最小二乘（PLS）回归从模拟分子光谱中提取同位素信息。在没有任何光谱干扰的情况下，并使用由11种同位素标准物组成的校准集，从100次激光发射中积累的信号的理论准确度和精确度分别约为C-的绝对百分比丰度为0.002％和0.001％。 13对于仅涉及三个和两个同位素标准品的校准，理论分析精度会稍有下降，但足以满足许多应用的需要，分别达到0.004％和0.008％。已经发现，PLS回归不仅能抵抗源闪烁和光子发射噪声，而且在区分光谱图谱与分析物谱图与光谱干扰谱图方面也很有效。模拟了来自单个或多个原子发射谱线的光谱干扰的影响，并提出并演示了将其影响最小化的新方法。已经发现，为计算归一化因子而选择的波长范围不应包含任何光谱干扰峰，并且适当选择的波长范围会使光谱干扰的容忍度提高至少一个数量级。使用与矩阵匹配的校准标准品，其精度（表示为确定的C-13同位素丰度的RSD）从无光谱干扰时的约千分之一降低到约千分之三，千分之十和每千分之20的样品具有多个光谱干扰峰，分别比分析物的分子带头强10倍，100倍和1000倍。研究得出结论，PIS回归是从LAMIS光谱中提取同位素信息的强大而必不可少的工具。 （C）2016 Elsevier B.V.保留所有权利。

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