直接粉末制样-小型偏振激发能量色散X射线荧光光谱法分析地质样品中多元素

采用小型偏振激发能量色散X射线荧光光谱仪,直接粉末制样法,分析了硅酸盐类岩石、土壤、沉积物样品.实验结果表明,主量元素的总分析精度优于2%RSD,主要受制样精度控制.不同含量的痕量元素的总分析精度一般优于5%RSD,含量低时可达约20%RSD.制样精度(方差)在分析总精度(方差)中所占的比例一般大于50%,且元素原子序数越小、含量越高(计数统计涨落小),所占的比例越大.实验还表明,对于大多数元素,在样品量大于1 g后,分析结果变化不显著;但Ba等重元素在样品量小于5 g时结果受样品量影响显著;实际分析中可以不必称量样品,但应保证所使用的样品量大于5 g.通过作为未知样品分析的标准参考物的分析结果和参校标准物质的回算结果的综合考察,并参照中国地质调查局多目标地球化学调查规范(1:25万),该方法在常规情况下可定量分析K、Ca、Ti、V、Cr、Mn、Fe、Ni、Cu、Zn、Ga、As、Rb、Sr、Y、Zr、Nb、Ba、Pb、Th等20个元素,过渡金属元素的测定限在10 mg/kg左右.由于制样方法简单,无需制样设备,该方法适合于车载野外现场快速分析.

Multi-element Determination in Geological Materials by Bench-top Polarized Energy Dispersive X-ray Fluorescence Spectrometry Coupled with Directly Pressed Powder Sample Preparation Technique

A bench-top type polarized energy dispersive X-ray fluorescence spectrometry coupled with directly pressed powder sample has been used to analyze silicate rocks, soils and sediments. The experimental results show that about 50 elements can be simultaneously monitored, among which 20 elements (including K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, As, Rb, St, Y, Zr, Nb, Ba, Pb, Th) can be quantified in accordance with the regulation on multi-purpose geochemical survey (1 : 250 000) issued by China Geological Survey. The analytical precision for major elements is better than 2% RSD and mainly affected by sample preparation. For most elements with analytical line energies lower than that of the Compton line of Mo Ka which is used as internal standard, no obvious variation of the results is observed when sampling mass excesses 1 g. But for heavier elements such as Ba and Sn, the variation of the results is remarkable when sampling mass is less than 5 g due to higher energy K lines are used for measurements. In practice, sampling mass need not be controlled when sampling mass excesses 5 g. The method is suitable for on-site geochemical analysis for its simplicity and powerful measurement capability.