基于基本参数法的EDXRF全谱拟合定量算法及其应用

An EDXRF Quantitative Algorithm Based on Fundamental Parameters and Spectrum Unfolding

在进行能量色散X射线荧光(EDXRF)的解谱操作时,如果样品中元素含量不高,单个元素的谱峰形状在混合样品谱中会保持较好,纯元素谱剥离是一种比较好的解谱方法,同时,在不高的含量范围内,谱峰强度与元素含量的线性关系保持较好,定量较为准确;但在常量分析中,元素之间会存在较强的吸收增强效应,并导致混合样品谱中单个元素的贡献与其纯元素谱的形状不一致,因此,用固定形状的纯元素谱剥离方法就会有较大偏差。同时,吸收增强效应会干扰谱峰强度与元素含量的线性关系,两种因素的叠加,导致元素定量的不准确,因此,在进行常量分析时,简单的纯元素谱剥离的解谱方法并不适用。介绍了一种基于基本参数(FP)法的全谱拟合定量算法,在进行谱图准确拟合的同时,完成定量计算,其操作步骤如下:首先用纯元素谱剥离的方法得到实测的各谱线强度,并以此为依据预估样品中各元素含量,然后代入FP法计算样品中各谱线理论强度,根据与实测值的偏差调整元素含量,并做“FP计算-调整含量”两个过程的迭代,直至计算谱与实测谱的强度无差别;用最后的样品构成计算各元素谱峰形状,并修正纯元素谱,再次重复“剥离解谱-估算含量-迭代FP计算”的步骤,将最终得到的元素含量认为是测试结果。该种方法弥补了简单解谱剥离方法的弊端,借助于基本参数法的计算,纯元素谱峰得到了修正,解谱更准确,同时也能很好地校正基体效应对定量分析的影响。利用这种方法对较高浓度La/Ce/Pr/Nd混合溶液样品的EDXRF谱图进行分析,新方法计算得到的谱图与实测谱的残差σ降至474.5,远小于单纯使用纯元素谱剥离方法的1415.0[1]。用该方法对多个配分含量范围从0~90%的稀土混合溶液进行检测,各样品各元素配分偏差均小于1%,多次连续测试表明,各元素的相对标准偏差RSD<1%,该方法的准确度和稳定性都较好,能很好地满足稀土冶炼行业生产实践的需求。

In the analysis of spectrum for energy dispersive X-ray fluorescence(EDXRF),if the contentof elements is not high in the sample,the peak will keep its original shape as the pure element,peeling the spectrum of pure elements is a good way.Meanwhile,the linear relationship between peak intensity and element content is reliable,and the quantitative analysis is accurate.But in constant analysis,there usually has obvious absorption and enhancement effect between elements,which lead to a different spectrum for the element in the mixed sample compared with pure element spectrum,hence,usingthe fixed shape of pure element spectrum peeling methods will have greater deviation.At the same time,the linear relationship between peak intensity and element content will be disturbed by the absorption enhancement effect.The superposition of the two factors leads to the inaccuracy of element quantification.Therefore,in constant analysis,the simple spectral peeling method is not suitable.This article introduces a full spectrum fitting quantitative algorithm based on the Fundamental Parameter(FP)method,which can fit the spectrum accuratelyandrealize the quantitative calculation at the same time.The process is as follows:firstly,the measured intensity for each line was obtained base on pure element peeling method,and which was used to estimate the content for elements in the sample,and then the theoretical intensity of each spectral line was calculated in the sample using FP method.The element content was adjusted according to the deviation of the measured value,and the two processes of“FP calculating content Adjusting”were iterated until the intensity of the calculated spectrum has no different from the measured spectrum.The obtained sample composition was used to calculate the shape of spectrum intensity for each element.In the meantime,the pure element spectrum was modified.And the steps of“peeling spectrum-estimating content-iterating FP calculation”was repeated.After that,the final element content was considered the test result.This method was used to analyze La/Ce/Pr/Nd spectra in mixed solution samples for about 250 g·L^(-1) based on EDXRF.The residual error between the calculated spectra and the measured spectra was reduced to 474.5,which was less than the 1415.0[1]for using the pure element spectral stripping method alone.The method is applied to the determination of several rare earth mixed solutions with the partition content ranging from 0%to 90%,and the deviation of each element in each sample is less than 1%.For a successive test,each element’s relative standard deviation(RSD)was less than 1%.The actual measurement shows that the accuracy and stability of the method are good,which can well meet the needs of the rare earth hydrometallurgy industry.