熔融制样XRF法测定海洋沉积物中10种主量元素的条件优化

Optimum conditions for the determination of 10 main elements in marine sediments by the fused bead-X-ray fluorescence spectrometry

采用四硼酸锂-偏硼酸锂混合熔剂(67∶33),硝酸锂为氧化剂,溴化锂为脱模剂,熔融制作样片,利用X射线荧光光谱仪,用土壤、水系沉积物和海洋沉积物等标准物质拟合校准曲线,系统研究了熔剂、稀释比、脱模剂、熔融温度与时间对测定结果的影响,并分析了产生这些影响的机理,优化改进了X射线荧光光谱(XRF)法同时测定海洋沉积物中主量组分(Na2O、MgO、Al2O3、SiO2、P2O5、K2O、CaO、Fe2O3、MnO、Ti2O)的分析方法。结果表明,当样品与混合熔剂在熔融稀释比例为1∶10的条件下混合均匀,在700℃预氧化200 s,升温至1050℃熔融10 min,实验优化获得高质量的熔片,较大的稀释比与未知烧失量(loss on ignition,缩写为LOI)校正结合,无需对样品烧失量进行校正,简化了分析步骤。对海洋沉积物标准物质GBW07314进行精密度考察,各组分含量的相对标准偏差(RSD)为0.32%~2.05%,方法检出限为70~270μg/g。对海洋沉积物、水系沉积物、岩石矿物和土壤4类标准样品进行准确度考察,测定值与标准推荐值无显著性差异。表明方法准确可靠,能满足地质与地理类海洋沉积物、水系沉积物、岩石矿物和土壤等样品准确定量分析。

In this thesis, a method for the determination of major elements(including Na2O, MgO, Al2O3, SiO2,P2O5, K2O, CaO, Fe2O3, MnO, and Ti2O) in marine sediments by the X-ray fluorescence(XRF) spectrometry is optimized. In the experiment, the Li2B4O7-LiBO2 mixture [m(Li2B4O7)∶(LiBO2)=67∶33] is adopted as the flux, LiNO3 as the oxidant, and LiBr as the mold discharging agent. Under the above condition, the sample was prepared by melting. Meanwhile, the calibration curves were constructed, through applying the certified reference materials, such as soil, stream sediment, and marine sediment by X-ray fluorescence spectrometer.Moreover, the effects of flux, dilution ratio, remolding agent, melting temperature, and melting time on the determination results, were systematically studied. The results show that high-quality fuses were obtained under the following conditions: the sample and the mixed flux was uniformly mixed;the melt dilution ratio is 1∶10;the mixture was pre-oxidized at 700 ℃ for 200 seconds and melted at 1050 ℃ for 10 minutes. The loss on ignition(LOI) detection was not necessary while a relative large dilution ratio combined unknown LOI correction was adopted, which greatly simplified the test method. Testing with the marine sediment standard substance GBW07314, we find that the relative standard deviation(RSD) of each component content was 0.32%~ 2.05%, and the detection limit of the method was 70~ 270 ug/g. In the accuracy of the artificial standard sample, there was no significant difference between the measured value and the recommended value.The results reveal that the method is accurate and reliable, which can be utilized for accurate quantitative analysis of geological and geographic stream sediments, rocks, minerals, soils, and other samples., rocks,minerals, soils, and other samples.