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粉末压片-X射线荧光光谱法测定小样品量土壤和沉积物中主量元素

Determination of Major Elements in Small-Weight Soil and Sediment Samples by X-ray Fluorescence Spectroscopy with Pressed-Powder Pellets

  • 摘要: 实现小样品量的X射线荧光光谱(XRF)分析测试是获取珍贵和稀缺样品中化学组成过程需要解决的关键技术问题。同时,应用XRF对标准物质进行均匀性检验在最小取样量上也存在争议。在目前地质分析样品(包括标准物质)大多为74μm(−200目)粒度水平下,XRF分析压片法的常规样品量为4g左右。本文利用0.1g样品量进行粉末压片,通过更换XRF试样盒面罩直径为12mm,缩小视野光栏直径为10mm,同时在优化制样条件和仪器测量条件基础上,利用32种不同类型、不同含量梯度的地球化学标准物质,建立了0.1g样品量条件下XRF粉末直接压片法测定土壤和沉积物样品中10种主量元素(SiO2、Al2O3、TFe2O3、MgO、CaO、Na2O、K2O、Mn、Ti和P)的分析方法,大幅度降低了样品量。0.1g样品量分析方法检出限为14μg/g~0.35%,精密度(RSD,n=12)小于3.9%。经对比分析,采用本文0.1g样品量方法分析不同含量标准物质的测定值均在标准值范围内,相对误差绝对值(|RE|)在0~15.7%,与4g样品量分析结果(|RE|在0.3%~28.3%)差异不大。采用本文方法0.1g样品量和常规方法4g样品量两种方法分析实际样品的测定结果基本吻合,验证了建立的0.1g样品量XRF分析方法可靠。

     

    Abstract: The analysis of small-weight samples utilizing X-ray fluorescence spectrometry (XRF) poses a pivotal technical challenge in determining the chemical composition of valuable and scarce materials. Furthermore, the application of XRF to verify the homogeneity of reference materials has sparked debates regarding the minimum sample weight. Presently, geological samples, encompassing reference materials, predominantly adhere to a particle size of 74μm (-200 mesh). In the context of XRF analysis employing pressed-powder pellets, the conventional sample weight is approximately 4g. In this paper, 0.1g weight soil or sediment was used for pressed-powder pellet preparation. The diameter of the XRF spectrometry sample box mask was changed to 12mm, and the diameter of the field view light barrier was reduced to 10mm. Based on the previously optimized instrumental measurement conditions, we successfully established a 0.1g sample weight analytical method for the quantification of ten major elements (SiO2, Al2O3, TFe2O3, MgO, Cao, Na2O, K2O, Mn, Ti, and P) utilizing wavelength dispersive X-ray fluorescence (XRF) spectroscopy, which significantly reducing the necessary sample weight. This methodology employed a diverse range of 32 geochemical reference materials, encompassing various types and content gradients. The detection limit of the 0.1g sample weight analysis method was between 14μg/g and 0.35%, and the precision (RSD, n=12) was less than 3.9%. Through comparative analysis, the results of the reference materials were all within the standard value range, and the absolute value of relative error (|RE|) was between 0 and 15.7%. There was no significant difference with the 4g sample weight analysis results (|RE| ranged from 0.3% to 28.3%). The practical sample results determined by the method of 0.1g sample and the conventional method of 4g sample are consistent. The established XRF method for the 0.1g weight sample is reliable.

     

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