熔融制样-X射线荧光光谱法测定菱镁矿中主次组分

实验采用熔融法制样,以X射线荧光光谱法(XRF)实现了菱镁矿中MgO、Al₂O₃、SiO₂、P₂O₅、CaO、TiO₂、MnO、Fe₂O₃主次量组分的测定。选择白云岩、水镁石和石灰石国家一级标准物质及人工合成校准样品绘制校准曲线解决了高含量MgO和低含量CaO的测定问题。先测量样品灼烧减量,用灼烧后的样品进行熔片,以消去灼烧减量的含量与X射线荧光强度建立校准曲线,并进行基体校正,测出未知样灼烧后的含量后,再换算为样品实际含量。灼烧后样品与熔剂Li₂B₄O₇的稀释比为1∶10,加入1滴LiBr溶液(1.0 g/mL)作为脱模剂,在1 050 ℃熔融9 min制备熔片。各组分校准曲线的相关系数在0.997 6~0.999 9之间;方法检出限在10~320 μg/g之间。对一菱镁矿实际样品进行精密度考察,各组分测定结果的相对标准偏差(RSD,n=12)在0.25%～3.6%之间。所建方法应用于菱镁矿标准物质和实际样品的测定,结果与标准物质认定值或实际样品湿法值基本一致。

Determination of major and minor components in magnesite by X-ray fluorescence spectrometry with fusion sample preparation

After the magnesite sample was prepared with fusion method, the content of MgO, Al₂O₃, SiO₂, P₂O₅, CaO, TiO₂, MnO and Fe₂O₃ in magnesite was determined by X-ray fluorescence spectrometry(XRF), realizing the simultaneous determination of major and minor components. The calibration curve was plotted with the national certified reference materials of dolomite, brucite and limestone and artificially synthetic calibration sample, solving the determination problems of high content MgO and low content CaO. The loss on ignition of sample was firstly measured. Then, the burned sample was prepared for fuse pieces. The calibration curve was established by the content after correction of loss on ignition and the corresponding X-ray fluorescence intensity, and the matrix correction was also conducted. Finally, the content in burned sample was determined to calculate the content in actual sample. The dilution ratio between the burned sample and flux (Li₂B₄O₇) was 1∶10. One drop of LiBr solution (1.0 g/mL) was added and used as releasing agent. The fuse piece was prepared at 1 050 ℃ for 9 min. The correlation coefficients of calibration curves of components were between 0.997 6 and 0.999 9. The detection limit of method was 10-320 μg/g. One actual magnesite sample was used for precision test. The relative standard deviation(RSD, n=12) of components were between 0.25% and 3.6%. The proposed method was applied to the determination of certified reference material and actual samples of magnesite, and the results were basically consistent with the certified values and those obtained by wet method.