粉末压片制样-X射线荧光光谱法测定土壤和水系沉积物中氯和溴

Cl和Br是土地质量调查和评价的重要指标,X射线荧光光谱法测定土壤和水系沉积物中Cl和Br的难点在于Cl容易污染,测量值易受测量时间、测量次数等因素影响,方法稳定性差;而Br的地球化学背景值低,方法准确性和稳定性较差。实验重点对Cl和Br元素的谱线选择、测量时间、基体校正以及Cl元素测量时样片的放置时间、测量次数和Br元素测量的方法稳定性进行研究,建立了粉末压片制样-X射线荧光光谱法测定(XRF)土壤和水系沉积物中Cl和Br的分析方法。待测样放置时间建议不超过48 h;推荐Cl的测量时间为24～30 s,Br的测量时间为30 s;Cl测量次数为1片1次。方法中,Cl无需进行谱线干扰校正,Br选用As扣除谱线干扰,用Rh-KαC线作内标;Cl、Br均采用经验系数法校正基体效应。Cl、Br检出限分别为20×10^-6和0.6×10^-6。以12个标准物质和一个未知样为考察对象,按照实验方法进行测定,Cl和Br结果的相对标准偏差(RSD,n=12)均小于10%;采用实验方法分析土壤和水系沉积物标准物质,测定值与认定值吻合良好。

Determination of chlorine and bromine in soil and stream sediment by X-ray fluorescence spectrometry with pressed powder pellet

Cl and Br were important indexes for the investigation and evaluation of land quality. The difficulties for determining Cl and Br in soil and stream sediments by X-ray fluorescence spectrometry were as follows: Cl was easily polluted, and its determination results was easily affected by determination time and the number of determination, then the stability of method was poor; the geochemical background value of Br was low, and the accuracy and stability of the method were poor. The spectral line selection, the determination time, the matrix correction of Cl and Br, the sample placing time and the numbers of determination of Cl, and the method stability for determination of Br were studied. Thus, a method for the determination of Cl and Br in soil and stream sediments was developed by X-ray fluorescence spectrometry (XRF) with pressed powder pellet. The recommended placing time for test sample was less than 48 h. The recommended determination time for Cl and Br was 24-30 s and 30 s, respectively. The number of determination for Cl was one piece at each determination. The correction of spectral interference for Cl was not necessary. For Br, As was selected to deduct the spectral interference, and Rh-KαC line was used as the internal standard. The empirical coefficient method was employed to correct the matrix effect for both Cl and Br. The limits of detection for Cl and Br were 20×10^-6 and 0.6×10^-6, respectively. Twelve reference materials and one unknown sample were determined according to the experimental method. The relative standard deviations (RSDs, n=12) for Cl and Br were both less than 10%. The certified reference materials of soil and stream sediment were determined according to the experimental method, and the results were consistent with the certified values.