粉末压片制样-波长色散X射线荧光光谱法测定土壤和水系沉积物中溴氯氟磷硫

采用粉末直接压片制样,波长色散X射线荧光光谱法(WD-XRF)同时测定土壤及水系沉积物样品中的Br、Cl、F、P和S时,5种待测元素受矿物、化学态和粒度效应影响,测试难度较大。实验选择水系沉积物和土壤标准物质建立校准曲线,Br采用经验系数法和Rh Kα康普顿散射内标法校正基体效应和谱线干扰,F采用经验系数法和F背景内标法进行校正,Cl、P和S采用经验系数法进行校正,可以实现5种元素的准确测定。研究发现,Cl的测定值随重复测定次数的增加而增大,当Cl的质量分数达到4 800 μg/g时测定值不受测量次数的影响;为了保证分析结果的准确性,样片只能测定1次,并以第1次测定结果为准,且样片应及时测量或者放入干燥器中待测;此外,价态对S荧光强度的影响不是主要因素,矿物效应化学态和粒度效应可能是最主要的干扰因素。确认了As Kβ对Br Kα,Mo Lγ1对Cl Kα,Mo Lα对S Kα以及Y Lβ1对P Kα存在谱线干扰,并采用经验系数校正干扰。对土壤和水系沉积物标准物质中5种元素进行测定,结果的相对误差(RE)均小于11%,相对标准偏差(RSD)均小于6%,其检出限和准确度均达到行业标准DZ/T 0258—2014的要求,适用于测定大批量的地质样品。

Determination of bromine,chlorine, fluorine,phosphorus and sulfur in soil and stream sediment by wavelength dispersive X-ray fluorescence spectrometry with pressed powder pellet

When the contents of bromine, chlorine, fluorine, phosphorus and sulfur in soil and stream sediment are determined simultaneously by wavelength dispersive X-ray fluorescence spectrometry(WD-XRF) with direct pressed powder pellet method, these five elements will be affected by mineral, chemical state and particle size effect. Therefore, the determination difficulty is relatively high. In experiments, the certified reference materials of stream sediment and soil were selected to establish the calibration curve. The empirical coefficient method and Rh Kα Compton scattering internal standard method were used to correct the matrix effect and spectral line interference during the determination of Br. The empirical coefficient method and F background internal standard method were used for correction during the determination of F. The testing of Cl, P and S could be corrected by empirical coefficient method. Consequently, the accurate determination of five elements were realized. It was found that the testing value of Cl increased with the number of repeated detections. When the Cl content was up to 4 800 μg/g, the measured value was not affected by the number of measurements. In order to ensure the accuracy of the analysis results, the sample could only be measured once, and the first measurement result shall prevail. Moreover, the sample should be measured in time or placed in a desiccator for testing. In addition, the influence of valence state on the fluorescence intensity of S was not the main factor, while the mineral effect chemical state and particle size effect were possibly the most important interference factors. It was confirmed that As Kβ line overlapped with Br Kα line, Mo Lγ1 line overlapped with Cl Kα line, Mo Lα line overlapped with S Kα line, and Y Lβ1 line overlapped with P Kα line. The interference was corrected by empirical coefficients. Five elements in the certified reference materials of stream sediment and soil were determined. The relative errors (RE) of determination results were all less than 11%, and the relative standard deviations (RSD) were less than 6%. The limit of detection and accuracy could meet the requirements of industrial standard (DZ/T 0258-2014). The proposed method was suitable for measuring large quantities of geological samples.