利用粒度重组方法克服X射线荧光光谱粉末压片法的基体效应

采用X射线荧光光谱粉末压片法测定铝铁中铝时,由于粒度效应的影响,铝测量结果的准确度降低。通常,采用单一控制样品粒度小于0.075 0 mm的制样方法来克服粒度效应时,铝的X射线荧光强度的相对标准偏差(RSD,n=10)达到4.3%。在大量试验的基础上,提出了一项粒度重组技术,即通过调整样品中的0.250～0.125 mm、0.125～0.075 0 mm、0.075 0～0.045 0 mm、＜0.045 0 mm 4个粒度等级的质量占比为2∶2∶1∶5后,铝的X射线荧光强度的RSD(n=10)降为1.2%,有效降低了粒度效应的影响。从粒度调整对测定结果的影响、两种制样方法对测量强度的影响、不同制样方法样片表面差异、不同分析方法准确度的显著性差异4个方面进行讨论,证明粒度重组方法能有效地消除粒度效应对粉末压片法结果的影响,铝铁中铝的测定结果与EDTA滴定法的结果准确度无显著性差异。

Application of particle size recombination method for overcoming matrix effect of X-ray fluorescence spectrometry with pressed powder pellet

During the determination of aluminum in ferro-aluminum by X-ray fluorescence spectrometry(XRF) with pressed powder pellet, the detection accuracy will be reduced due to the influence of particle size effect. Usually, when a single sample preparation method with sample size less than 0.075 0 mm is adopted to overcome the particle size effect, the relative standard deviation (RSD, n=10) of X-ray fluorescence intensity of aluminum is up to 4.3%. Based on many experiments, a method of particle size recombination was proposed in the study. The mass ratio of sample with four particle sizes, i.e., 0.250-0.125 mm, 0.125-0.075 0 mm, 0.075 0-0.045 0 mm and less than 0.045 0 mm, was adjusted to 2∶2∶1∶5. Accordingly, the RSD(n=10) of X-ray fluorescence intensity of aluminum was reduced to 1.2%, which effectively reduced the influence of particle size effect. Four aspects were discussed, including the particle size recombination on determination results of aluminum, the influence of two sample preparation methods on measuring intensity, the sample surface difference of different preparation methods, and the significance difference accuracy of different analysis methods. It indicated that the proposed particle size recombination method could effectively eliminate the influence of particle size effect on the results of pressed powder pellet. The determination results of aluminum in ferro-aluminum by proposed method had no significant difference with the determination accuracy of EDTA titration.