基于X射线荧光光谱分析水稻籽粒离子组

Simultaneous analysis of ionome in rice grains based on X-ray fluorescence spectrometry

【目的】水稻籽粒离子组通常采用电感耦合等离子体质谱(ICP-MS)和电感耦合等离子体发射光谱(ICPOES)等技术进行分析,需要破坏性取样且样品前处理过程复杂。X射线荧光光谱法(XRF)一般无需进行样品处理,可以快速无损地检测样品中的元素含量。本研究建立和优化了利用XRF进行水稻籽粒离子组分析的方法。【方法】通过比较不同的试验条件对水稻籽粒中不同元素XRF谱图的影响,确定适合进行XRF分析的元素及试验条件,通过与ICP-MS定量结果的相关性分析,检验XRF定量方法的适用性、定量结果的准确性。【结果】在样品室抽真空时,光源在30 kV和600μA并且不使用滤光片的条件下,使用50μm步长面扫描时,样品中的P、S、Cl、K、Ca、Mn、Fe和Zn等元素信号与背景对比明显。同时,XRF扫描获得的Mn和Zn的荧光定量结果与ICP-MS的测定结果具有较高的相关性,线性拟合的决定系数分别为0.8415(P<0.001)和0.7736(P<0.001)。采用优化的分析条件,水稻籽粒中Cd的两条特征谱线La和Ka分别受到K和Mn信号的压抑,不能用于Cd含量的定量分析。【结论】采用优化的试验条件,XRF方法可以无损地同时测定稻米中多个营养元素,特别是锌和锰。但由于Cd特征图谱与稻米中含量较高的K和Mn接近,信号无法清楚识别,因此,XRF仪无法快速测定水稻籽粒中Cd含量是否超标。

【Objectives】The ionomic profile of rice grain is usually characterized by techniques such as inductively coupled plasma mass spectrometry(ICP-MS)and inductively coupled plasma emission spectrometry(ICP-OES),which require complicated sample preparation and cannot analyze samples non-destructively.On the contrary,X-ray fluorescence spectrometry(XRF)does not require sample preparation and can detect the elemental content of a sample directly.The purpose of this study was to optimize experimental conditions of XRF for the quantitative analysis of elements in rice grains.【Methods】The determining conditions of XRF spectra for individual element in rice grains were compared and then optimized,according to the results.The applicability and accuracy of quantitative results of XRF measurement were evaluated by correlating them with ICP-MS results.【Results】Using filter-free scanning at a 50μm step,with a light source of 30 kV,and a current of 600μA under vacuum,the signals of P,S,Cl,K,Ca,Mn,Fe were distinctly different from the background noise signals.The quantification of XRF signals for Mn and Zn was highly correlated with their concentrations determined by ICP-MS,the determination coefficients of the linear fitting equations were 0.8415(P<0.001)and 0.7736(P<0.001),respectively.For Cd detection,the two spectrum signals,La and Ka,were very close to that of K and Mn,respectively.Cd had two spectrum,La and Ka;the La spectrum was very close to that of K,making it unable to differentiate from K,and the Ka spectrum was close to that of Mn,which was pressed completely by Mn signal and could not be isolated.【Conclusions】Under the optimized conditions,XRF scanning can be used to quantitatively determine the concentration of multiple elements,except for Cd,in rice grains simultaneously and non-destructively,particularly for Mn and Zn.