土壤中元素活动态的全反射X射线荧光光谱分析

doi:10.3964/j.issn.1000-0593(2020)07-2278-05

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Abstract Delineating abnormity zones of elements in mobile forms is one of the effective methods of deep-penetrating geochemistry for finding concealed orebodies, which can obtain deep mineralization information and predict the supply of metallogenic materials. However, samples have to be transported to the laboratory for analysis under conventional experimental techniques. Transportation process and time may affect the concentration of the elements of mobile forms. Moreover, the large amount of samples required for conventional analysis limits the study of extraction time of mobile forms. Total reflection X-ray fluorescence spectrometry (TXRF) has the advantages of high sensitivity, simple quantification and less dosage. With characteristics of the compact and portable instrument as well as no need for carrier gas and cooling water, TXRF is suitable for on-site analysis. In this paper, TXRF was used to establish a method for the analysis of mobile forms of Ti, V, Mn, Fe, Ni, Cu, Zn, Rb, Sr, Y, Ba, Ce and Pb in soils, by selecting internal standard and controlling quality. Because of the high content of organic matter in the extract, the concentration of internal standard Se was set higher (10 μg·mL^-1 Se in the analytical solution), so as to improve the analytical accuracy of Se under high background. In order to control the pollution and reduce the error, blank reflectors were analyzed by TXRF for 100 s. The reflectors without impurity peak were used for the experiment. The main steps list as follows: (1) 5 g soil samples were mixed with 50 mL polymetallic extractant (0.09 mol·L^-1 ammonium oxalate, 0.1 mol·L^-1 ammonium citrate, 0.001 mol·L^-1 EDTA, 0.001 mol·L^-1 DTPA, 0.001 mol·L^-1 NTA, 0.005 mol·L^-1 TEA). The mixture was oscillated for 72 h at room temperature and then filtered with 0.45 μm filter membrane. (2) The 100 μL of filtrate (extract) was spiked with 10 μL internal standard of 100 μg·mL^-1 Se. (3) After vortexing, 10 μL drop of aqueous solution was deposited onto a siliconized quartz glass reflector and dried at 50 ℃ for TXRF analysis (monochromatic excitation of Mo-Kα, measure time 1 000 s). The results showed that the detection limit of elements ranged from several to dozens of μg·L^-1. The RSD of most elements wa less than 10%. The average relative error was 18% compared with ICP-MS/ICP-OES. This method is suitable for rapid on-site analysis of elements mobile forms. 10 μL drop of 100 μL prepared samples to make it suitable for time experiment of mobile forms by using small volume continuous sampling, with high efficiency, relatively strong continuity and minor error.

Key words：Mobile forms of element; Total reflection X-ray fluorescence spectrometry; Deep-penetrating geochemistry; Small volume samples; On-site analysis

Received: 2019-06-12 Accepted: 2019-10-29

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O657.34

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2020)07-2278-05 OR https://www.gpxygpfx.com/EN/Y2020/V40/I07/2278