X射线荧光光谱法测定白云石、石灰石中氧化钙、氧化镁和二氧化硅

将白云石、石灰石标准样品直接压片, 通过灼烧减量对氧化钙、氧化镁和二氧化硅含量进行校正, 根据其含量与强度的对应关系绘制校准曲线, 建立了X射线荧光光谱法(XRF)测定白云石、石灰石中这3种主要成分的方法。对一部分试样直接压片测定, 同时另一部分试样进行灼烧减量试验, 可大大节约标准样品的用量。灼烧时间试验表明, 试样在1 100 ℃下灼烧0.5 h就可达到恒重;粒度试验表明, 样品粒度大于200目时可消除粒度效应的影响。用CaO和MgO含量进行基体校正, 可消除其对低含量SiO₂的影响;采用经验系数法可消除元素间的吸收-增强效应。精密度试验结果表明, 氧化钙、氧化镁和二氧化硅测定结果的相对标准偏差(n=8)在0.038%~3.5%之间;对石灰石和白云石标准样品和实际样品进行准确度考察, 测定值与认定值或滴定法的测定值一致。

Determination of calcium oxide,magnesium oxide and silicon dioxide in dolomite and limestone by X-ray fluorescence spectrometry

Certified reference material of dolomite and limestone underwent direct compression, and the contents of calcium oxide, magnesium oxide and silicon dioxide were corrected by loss on ignition, so the calibration curve was plotted based on the correspondence between its content and intensity, and thus the method for the determination of three main components of dolomite and limestone by X-ray fluorescence spectrometry(XRF) was established. One portion of the sample could be determined after direct compression while another portion could be analyzed with the loss on ignition test, so the dosage of the certified reference materials could be significantly reduced. The tests on ignition time showed that when the analyte was burned for 0.5 h at 1 100 ℃, its weight could become constant; and the tests on granularity showed that when the sample size surpassed 200 mesh, the granularity effect could be eliminated. Matrix correction with the CaO and MgO contents could eliminate its influence on low-content SiO₂; and the adoption of experiential coefficient method can eliminate the absorption-enhancement effect among the elements. Precision test results indicated that calcium oxide, magnesium oxide and silicon dioxide measurement results had relative standard deviations (n = 8) in the range of 0.03 8 %-3.5 %; certified reference materials of limestone and dolomite as well as actual samples were tested to determine the accuracy of the method, and it was found that the measured values were consistent with the certified values or those obtained by titration method.