直接粉末进样-能量色散X射线荧光光谱法测定地质样品中多种组分

为提高现场快速分析的能力,充分发挥小型实验室设备的功能,实验采用能量色散X射线荧光光谱仪,直接使用粉末样品分析常规地质样品中的多种组分。用理论α系数和康普顿内标校正基体效应和谱线重叠干扰,直接将粉碎加工到200目(74μm)的样品放在液体塑料盒中进行测量。对地质样品标准物质进行样品用量试验表明,样品用量大于3.0g时,测量结果趋于稳定或者在认定值的准确度控制范围内变动,实验时选取4.0g作为样品用量。精密度试验表明,除组分La、Ce、Sn、W、U和Na_2O的相对标准偏差(RSD,n=12)大于10%外,其他组分的RSD都小于10%,尤其是组分Ti、Mn、Co、Rb、Sr、SiO_2、K_2O、CaO和Fe_2O_3的RSD都在1%以下。通过对未参加回归的标准物质的验证,参照《地球化学普查(比例尺1∶50 000)规范样品分析技术要求补充规定》,该法对常规地质样品可定量分析Ti、V、Mn、Co、Ni、Cu、Zn、Ga、As、Rb、Sr、Y、Zr、Nb、Th、U、K_2O、CaO和Fe_2O_3等19种组分,近似定量分析Ce和W,半定量分析Cr、La、Sn、SiO_2和Na_2O。由于将样品放入液体塑料盒中进行测量,无需压片制样设备,该法适合野外现场分析应用。

Determination of multi-components in geological samples by energy dispersive X-ray fluorescence spectrometry coupled with direct powder introduction

In order to improve the rapid analysis ability in field and perform the functions of small laboratory equipments, several components in conventional geological samples were directly analyzed by energy dispersion X-ray fluorescence spectrometer with powder samples. The matrix effect and spectral overlapping interference were corrected by theoretical α coefficient and Compton internal standard method. The samples were directly pulverized into 200 mesh (74 μm) followed by determination in liquid plastic case. The dosage of sample was tested with certified reference materials of geological sample. The results indicated that the determination values trended to stable or to be varied in accuracy range of certified values when more than 3.0 g of sample was used.Thus, 4.0 g of sample was used for experiments. The precision tests showed that the relative standard deviations (RSD, n=12) of La, Ce, Sn, W, U and Na₂O were higher than 10%, while the RSDs of other components were less than 10%. Especially the RSDs of Ti, Mn, Co, Rb, Sr, SiO₂, K₂O, CaO and Fe₂O₃ were less than 1%. The proposed method was verified with the certified reference materials which were not used for regression. According to the supplemental provisions of samples analytical requirements norm for geochemical reconnaissance (scale of 1∶50 000), the proposed method could be used for the quantitative analysis of 19 components in conventional geological samples (including Ti, V, Mn, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Th, U, K₂O, CaO and Fe₂O₃), the approximately quantitative analysis of Ce and W, and the semi-quantitative analysis of Cr, La, Sn, SiO₂ and Na₂O. The sample could be put into liquid plastic case for measurement without sample preparation. Therefore, the proposed method was applicable for analysis in field.