便携式X射线荧光光谱仪现场测定 萤石矿伴生锑矿样品中钙

便携式X射线荧光光谱仪(PXRF)具有检测速度快、多元素同时测定等优点,已在各种现场检测中得到大量应用。但地质样品矿物伴生类型丰富、基体复杂、各元素之间极易产生干扰,让便携式X射线荧光光谱仪的现场应用受到一定限制。以贵州某萤石矿伴生锑矿区为例,便携式X射线荧光光谱仪现场分析萤石矿伴生锑矿样品中钙,由于仪器应用软件设计不足及仪器能量分辨率所限,样品中元素锑的特征谱线能量叠加在钙元素的特征谱线能量上而使钙的检测结果偏高,实际样品检测发现,偏高程度与样品中锑的含量具有相关性。实验经过回归趋势分析及乘幂方式回归,得出公式y=0.3519x^0.8881(x表示便携式X射线荧光光谱仪测试出锑的含量,y表示受锑影响的假象钙的含量),相关系数R²为0.9992。根据测得的总钙减去假象钙即得实际钙的含量。实际验证15件样品,经校正后的测试结果与室内EDTA滴定法测试结果基本吻合。方法检出限为0.077%,相对标准偏差(RSD)为1.2%,测定范围3%~30%。实验方法很好地解决了该矿区现场对钙元素含量的检测,可快速指导找矿工作圈定矿体,节约了大量成本及时间。

On-site determination of calcium in fluorite associated antimony ore sample by portable X-ray fluorescence spectrometer

The portable X-ray fluorescence spectrometer (PXRF) has many advantages such as rapid detection speed and simultaneous determination of multi-elements, and it has been widely used in various on-site tests. The geological samples usually contain abundant associated minerals and complex matrix. Moreover, the interference is very easily caused among elements. Therefore, the on-site application of PXRF is limited. One fluorite associated antimony ore sample from Guizhou was selected as an example for the on-site analysis of calcium by PXRF. Due to the insufficient design of application software and the limitation of energy resolution of instrument, the energy of characteristic spectral line of antimony in sample was superposed on the characteristic spectral line of calcium, leading to higher detection result of calcium. The determination of actual sample indicated that the degree of deviation was relevant to the content of antimony in sample. By regression trend analysis and exponentiation regression, the equation of y=0.3519x^0.8881 (x presented the content of antimony measured by PXRF, while y presented the content of false calcium which was affected by antimony) was obtained with correlation coefficient of R²=0.9992. Then, the actual content of calcium could be obtained by subtracting false calcium from total calcium. 15 samples were analyzed for verification. It was found that the determination results after correction were basically consistent with those obtained by EDTA titration in laboratory. The detection limit was 0.077%, the relative standard deviation (RSD) was 1.2%, and the determination range was 3%-30%. The experimental method well solved the problem for the on-site detection of calcium in this mine area. It could rapidly guide the searching of ore body, saving much cost and time.