Trace element quantitation with EELS is a powerful tool for providing information about elemental distribution in biological and materials sciences. Linear least squares fit (LSF) to standards of the signal and the background is a widely used method for retrieving small signals superimposed on a large, slowly varying background. Theoretically, for most accurate background fitting, the fitting window should be as large as possible. However, when using a large window, there may be a mismatch between the fine structure of the standard and the measured background, due to instability of the instrument and the experimental conditions and radiation damage. This mismatch, distributed over the entire window, can severely affect the accuracy of the small signal extracted with LSF. To overcome this problem, a small window, slightly larger than the signal is often used. Fig. 1 shows the results of extracting a small Ca signal by using respectively, a large and a small window for fitting an EELS spectrum collected from a specimen containing 26.3 mmol/kg dry weight Ca.

中文翻译：

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使用适合鳗鱼的线性最小二乘法定量微量元素的最佳窗口大小

使用 EELS 进行痕量元素定量是提供有关生物和材料科学中元素分布信息的强大工具。信号和背景标准的线性最小二乘拟合 (LSF) 是一种广泛使用的方法，用于检索叠加在大的、缓慢变化的背景上的小信号。理论上，对于最准确的背景拟合，拟合窗口应尽可能大。但是，当使用大窗口时，由于仪器和实验条件的不稳定性以及辐射损伤，标准品的精细结构与测量的背景之间可能存在不匹配。这种分布在整个窗口上的失配会严重影响 LSF 提取的小信号的准确性。为了克服这个问题，一个小窗口，通常使用比信号稍大的信号。图 1 显示了分别使用大窗口和小窗口拟合从含有 26.3 mmol/kg 干重 Ca 的样品中采集的 EELS 光谱提取小 Ca 信号的结果。